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FAQ ENTRY DELETE


1. What is an Air Cooled transformer?
It is a transformer that uses "air" as the cooling medium. This term is abbreviated with the ANSI designati** AA, indicating open, natural draft ventilated c**structi**.


2. What is Ambient Noise Level?
The noise level of the surrounding area, measured in decibels (dB).


3. What is Ambient Temperature?
It is the inherent or existing temperature of the atmosphere surrounding a transformer into which its heat is dissipated.


4. What is an Ampere?
It is the unit of measurement for electric current flow.


5. What does ANSI stand for?
The American Nati**al Standards Institute Inc. - **e of the recognized organizati**s that specify the standards for transformers.


6. What is an Autotransformer?
It is a transformer that has **ly **e winding per phase, part of which is comm** to both the primary and sec**dary circuits.


7. What does the term Banked describe?
Two or **** single-phase transformers c**nected together to supply a three-phase load.


8. What does the term BIL mean?
Basic impulse level is a means to express the ability of the insulati** system to withstand high voltage surges.


9. What is a Buck Boost transformer?
It is a two-winding, single-phase transformer with low voltage sec**dary windings, which can be c**nected as an autotransformer. Used to raise or lower single and three phase line voltages by 10 - 20%.


10. What is a Cast Coil transformer?
A transformer with coils solidly cast in epoxy resin under vacuum in a mold. Also called cast resin or epoxy cast coil transformers.


11. What is a Center Tap?
It is a reduced capacity tap at the midpoint in a winding.


12. What makes up a Coil?
Turns of electrical grade wire or strip c**ductor material wound ** a form, referred to as a winding.


13. What is Coil Hot-Spot Temperature?
It is the absolute maximum temperature present in the transformer. This number is equal to the sum of the ambient temperature, temperature rise and a variable.
T Hot Spot = T ambient + T rise + (10-20) °C.


14. What is Comm** Mode?
An electrical noise or voltage disturbance, that occurs between all of the line leads and the comm** ground, or between the ground plane and either line or the neutral.


15. What is a Compensated Transformer?
It is a transformer with a turn's ratio that provides a higher than rated voltage at no load, and rated voltage at rated load. These transformers CANNOT be used for reverse feed.


16. What is the term C**tinuous Rating?
The c**stant load which a transformer can carry its rated primary voltage and frequency, without exceeding its specified temperature rise.


17. What is a C**trol Transformer?
It is a transformer that is designed to supply good voltage regulati** characteristics when low power factor or high inrush current is drawn. Usually referred to as an Industrial C**trol Transformer.


18. What is the Core of a transformer?
It is the electrical grade steel laminati**s, which carry the magnetic flux.


19. What is Core Loss?
Losses in watts caused by magnetizati** of the core and its resistance to magnetic flux when excited or energized at rated voltage and frequency. Also referred to as excitati** loss or no-load loss.


20. What is a Current Transformer?
It is a transformer generally used in c**trol or instrumentati** circuits for measuring current.


21. What is a Delta c**necti**?
The delta c**necti** is a standard three phase c**necti** with the ends of each phase winding c**nected in series to form a closed loop with each phase 120 degrees from the other.


22. What is a Delta-Wye c**necti**?
A Delta Wye is when the primary is c**nected in delta and the sec**dary in Wye when pertaining to a three-phase transformer bank or three-phase transformer.


23. What are "Dielectric Tests"?
These tests c**sist of the applicati** of a voltage higher than the rated voltage for a specified time, for the purpose of determining the adequacy against breakdowns of insulating materials and spacing under normal c**diti**s.


24. What is a "Dry Type" transformer?
A dry type transformer is **e in which the transformer core and coils are not immersed in a liquid.


25. What is a "Dual Winding"?
A winding c**sisting of two separate parts which can be c**nected in series or parallel. Also referred to as dual voltage or series-multiple winding.


26. What is the "Efficiency" of a transformer?
The percentage of power transferred from the input of equipment to the output of equipment in Watts. (power out/power in x 100)


27. What is an "Electrostatic Shield"?
It is Copper or other c**ducting material placed between the primary and sec**dary winding and grounded to reduce electrical interference and to provide additi**al protecti**.


28. What is "Exciting Current (No-Load Current)"?
Current which flows in any winding used to excite the transformer when all other windings are open-circuited. It is usually expressed in percent of the rated current of a winding in which it is measured.


29. What does the term "Encapsulated" describe?
A transformer with its coils either encased or cast in an epoxy resin or other encapsulating materials.


30. What does the abbreviati** FCAN stand for?
"Full Capacity Above Normal." This designates that a transformer will deliver its rated kVA when c**nected to a voltage source that is higher than the rated voltage.


31. What does the abbreviati** FCBN stand for?
"Full Capacity Below Normal." Same as FCAN except that the taps are below rated voltage.


32. What is a Fan Cooled transformer?
A transformer cooled mechanically to maintain its rated temperature rise, typically using auxiliary fans to accelerate heat dissipati**.


33. Describe a Flexible C**necti**?
A n**-rigid c**necti** used to reduce transmissi** of noise and vibrati**.


34. Describe Flux Density?
The magnetic field strength in the core, typically measured in Telsa or Gauss.


35. Explain Frequency?
** AC circuits, designates the number of times the polarity alternates from positive to negative and back again . . . such as 60 cycles per sec**d. Measured in Hertz.


36. What is a Full Capacity Tap?
A full capacity tap is **e through which the transformer can deliver its rated kVA output without exceeding the specified temperature rise.


37. What is a Grounding Transformer?
It is a special three-phase autotransformer for establishing a neutral ** a 3-wire delta sec**dary. Also referred to as a 'Zigzag' transformer.


38. Describe Grounds or Grounding?
C**necting **e side of a circuit to the earth through low resistance or low impedance paths.


39. What is a Harm**ic?
A Harm**ic is a sinusoidal comp**ent of a periodic wave having a frequency that is a multiple of the fundamental frequency. For example, a comp**ent whose frequency is twice the fundamental frequency is referred to as the sec**d harm**ic, (120 Hz is the 2nd harm**ic of 60 Hz).


40. What does the term Hertz (Hz) mean?
It is a term for AC frequency in cycles per sec**d.


41. What are High Voltage and Low Voltage windings?
These terms are used to distinguish the winding having the greater voltage rating from that having the lesser in two winding transformers.


42. Describe Hi Pot?
It is a high potential dielectric test impressed ** the windings to check insulati** materials and clearances.


43. What is Impedance?
It is the apparent resistance in a circuit to the flow of an alternating current analogous to the actual resistance to a direct current.


44. What is an Impulse Test?
It is a dielectric test that determines the BIL capability by applying high frequency, steep wave-fr**t voltage between windings and ground.


45. What is an Induced Potential Test?
It is a standard dielectric test that verifies the integrity of insulating materials and electrical clearances between turns and layers of a transformer winding.


46. What is Inductance?
It is a property that opposes a change in current flow.


47. What is Inrush Current?
It is an abnormally high transient current, caused by residual flux in the core, which maybe drawn when a transformer is energized.


48. What are Insulating Materials?
Those materials used to electrically insulate the transformer's windings, turn-to-turn or layer-to-layer, and other assemblies in the transformer such as the core and busswork.


49. What is an Isolati** Transformer?
It is a transformer that insulates the primary circuit from the sec**dary circuit. Also referred to as a two-winding or insulating transformer.


50. What is the abbreviati** KVA stand for?
"Kilovolt Ampere Rating" designates the output that a transformer can deliver for a specified time at rated sec**dary voltage and rated frequency without exceeding the specified temperature rise. (1 kVA = 1000 VA, or 1000 volt amperes)


51. What are Knockouts and what are they used for?
They are easily removable circle of metal in an enclosure that eliminates the need for punching holes for c**duit.


52. What is a Laminati**?
Thin sheets of special steel used to make the core of a transformer.


53. What is a Line Reactor?
It is an electrical device whose primary purpose is to introduce a specific amount of inductive reactance into a circuit, usually to reduce or c**trol current.


54. What is the term Load?
The load of a transformer is the power in kVA or volt-amperes supplied by the transformer.


55. What are Load Losses?
They are losses in a transformer, which are incident to load carrying. Load loses include I2R loss in the windings due to load current, stray loss due to stray fluxes in the windings, core clamps, etc., and to circulating currents (if any), in parallel windings.


56. What is a Mid-tap?
It is a reduced capacity tap midway in a winding. Also referred to as a 'Center tap'. Usually it is in the sec**dary winding.


57. Describe Moisture Resistance?
Materials or equipment c**structed or treated so that it will not be harmed readily by exposure to a moist atmosphere.


58. What does the abbreviati** NEC?
Nati**al Electric Code


59. What does the abbreviati** NEMA?
Nati**al Electrical Manufacturers Associati**.


60. What are No-Load Losses (Excitati** Losses)?
It is the loss in a transformer that is excited at rated voltage and frequency, but without a load c**nected to the sec**dary. No-load losses include core loss, dielectric loss, and copper loss in the winding due to exciting current.


61. What is Overload?
When a transformer is overloaded, excessive heat develops and the insulati** system begins to breakdown. Life expectancy of the transformer is decreased due to heat exceeding the rating of the insulati** system.


62. What is Parallel Operati**?
Single and three phase transformers may be operated in parallel by c**necting similarly marked terminals, provided their ratios, voltages, resistances, reactance and ground c**necti**s are designed to permit parallel operati**. Current and voltage angular displacements are also required to be the same in the case of three phase transformers.


63. Explain the term Phase?
It is a type of AC electrical circuit; usually single phase 2-wire or 3-wire, or three-phase, 3 or 4 wire.


64. What is Polarity?
It designates the instantaneous directi** of voltages in the primary compared to the sec**dary.


65. What is a Potential (Voltage) Transformer?
A transformer generally used in instrumentati** circuits for measuring or c**trolling voltage.


66. What is Power Factor?
It is the relati** of watts to volt amps in a circuit.


67. What are Primary Taps?
Taps added to the primary winding. (See Taps)


68. What is Primary Voltage Rating?
Designates the input circuit voltage for which the primary winding is designed.


69. What is a Primary Winding?
The primary winding is the winding ** the energy input (supply) side.


70. Describe the term Rating?
It is the design characteristics such as primary and sec**dary voltage, kVA capacity, temperature rise, frequency, etc.


71. What is Ratio in terms of Voltage?
It is a reference to either the primary to sec**dary winding turns ratio or to the voltage ratio of the transformer.


72. What is a Ratio Test?
It is a standard test of transformers to determine the ratio of the primary to sec**dary voltage.


73. What is Reactance?
It is the impedance comp**ent due to inductance and/or capacitance.


74. What is a Reactor?
A single winding device with an air or ir** core which, produces a specific amount of inductive reactance into a circuit, usually to reduce or c**trol current.


75. What is a Rectifier Transformer?
A transformer designed to supply AC input to a rectifier to obtain the desired DC output and have the ability to withstand the heating effects caused by rectifier commutati** or ripple.


76. What is RCBN - Reduced Capacity Below Normal?
It is taps that carry full-rated winding current **ly, thus reducing available power because of lower output voltage.


77. Define Regulati**?
Usually expressed as the percent change output voltage when the load goes from full load to no load at a given power factor.


78. What is a SCR?
It is a silic**-c**trolled rectifier.


79. Describe Saturati**?
Saturati** is a natural c**diti** in which an increase in current results in a decrease in inductance.


80. What is a Scott C**necti**?
It is a c**necti** for polyphase using two special single-phase transformers. Usually used to change from two-phase to three-phase or three-phase to two-phase.


81. What is Sec**dary Voltage Rating?
Designates the no-load circuit voltage for which the sec**dary winding (winding ** the output side) is designed.


82. What is a Sec**dary Winding?
The transformer winding c**nected to the load or output side.


83. Define Series/Multiple?
A winding c**sisting of two or **** secti**s which can be c**nected for series operati** or multiple (parallel) operati**. Also referred to as dual voltage or series-parallel.


84. What is a Short Circuit?
A short circuit c**diti** occurs when an abnormal c**necti** or relatively low impedance, whether made accidentally or intenti**ally, occurs between to points of different potential in a circuit.


85. What is a Solid State Device?
It is a device that c**tains comp**ents that do not depend ** electr**ic c**ducti** in a vacuum or gas. Semic**ductors or the use of otherwise completely static comp**ents such as resistors or capacitors performs the electrical functi** of a solid-state device.


86. What is a Step-Down Transformer?
It is a transformer where the high voltage winding (primary) is c**nected to the input or power source and the low voltage winding (sec**dary) to the output or load.


87. What is a Step-Up Transformer?
A transformer in which the low voltage winding (sec**dary) is c**nected to the input or power source and the high voltage winding (primary) is c**nected to the output or load.


88. What is a Tap?
A tap is a c**necti** brought out of a winding at some point between its extremities, usually to permit changing the voltage or current ratio.


89. What is a T-C**necti**?
A Scott c**nected three-phase transformer utilizing two primary and two sec**dary coils called the main and the teaser.


90. What is Temperature Class?
It is the maximum temperature that the insulati** can c**tinuously withstand. The classes of insulati** systems in a transformer are rated as follows:
Class 105°C
Class 150°C
Class 180°C
Class 220°C


91. What is Temperature Rise?
It is the increase over ambient temperature of the winding due to energizing and loading the transformer.


92. How do you calculate the Total Losses in a transformer?
It is the transformer electrical losses, which include no-load losses (core losses) and load losses (winding losses).


93. What is a Transformer?
It is a static electrical device, which, by electromagnetic inducti** transforms energy at **e voltage and current to another voltage and current at the same frequency.


94. Describe Transient?
It is a temporary or brief change in a given parameter. This is typically associated with input voltage or output load parameters.


95. What are some of the Tests performed ** transformers?
Normal, routine producti** tests include: (1) core loss; (2) load loss - winding or copper loss;
(3) Impedance; (4) hi-pot - high voltage between windings and ground; (5) induced - double induced two times voltage. Opti**al special tests include: (a) heat run - temperature testing;
(b) Noise tests - sound level measurement; (c) impulse tests - BIL tests: (d) partial discharge.


96. What is Transverse Mode?
It is electrical noise or voltage disturbance that occurs between phase and neutral (between lines), or from spurious signals across the metallic hot line and the neutral c**ductor.


97. What is the abbreviati** UL?
Underwriters Laboratories


98. Define VPI Impregnati**?
A vacuum and pressure impregnati** process using a resin which, is then oven cured to completely seal and protect the surface of a transformer and provides a str**g mechanical b**d. This process is standard ** all Hamm**d transformer products.


99. What is Voltage Regulati**?
The change in sec**dary voltage that occurs when the load is reduced from rated value to zero, with the value of all other quantities remaining unchanged. Regulati** may be expressed in percent (per unit) ** the basis of rated sec**dary voltage at full load.


100. What is Volt-Amperes (VA)?
It is the current flowing in a circuit multiplied by the voltage of the circuit. It is an expressi** of the output rating of a transformer.


101. What is a Wye C**necti**?
A standard 3-wire transformer c**necti** with similar ends of the single-phase coils c**nected. This comm** point forms the electrical neutral point and may be grounded.


102. What is a Zig Zag C**necti**?
It is a special transformer c**necti** comm**ly used in grounded transformers. See also grounding transformers.


103. What is a C**trol Transformer?
A c**trol transformer is an isolati** transformer designed to provide a high degree of sec**dary voltage stability (regulati**) during a brief period of overload c**diti** (also referred to as "inrush current"). C**trol transformers are also known as Machine Tool Transformers, Industrial C**trol Transformers or C**trol Power Transformers.


104. When you calculate the VA requirement of a Transformer, do you use the Primary or the Sec**dary Voltage?
When selecting the VA requirement, you use the Sec**dary Voltage.


105. Can you use a C**trol Transformer c**nected in reverse?
Yes, a c**trol transformer can be c**nected in reverse. However, keep in mind the output voltage will be less than it's rating, due to the compensati** factor of the windings.


106. Can a C**trol Transformer regulate the output voltage?
A c**trol transformer will not regulate the voltage. Output voltage is a functi** of the coil's turn ratio **ly, times the input voltage.


107. What is the benefit of "Vacuum Impregnati**" ** a Transformer?
All Hamm**d C**trol Transformers are vacuum impregnated with "VT Polyester Resin" and oven cured which seals the surface and eliminates moisture. Impregnating the entire unit provides a str**g mechanical b**d and offers protecti** from envir**mental c**diti**s.


108. Explain the "VA" or "Volt Ampere Output" Rating?
The VA or volt-ampere output rating designates the output that a transformer can deliver for a specified time at its rated sec**dary voltage and rated frequency, without exceeding its specified temperature rise.


109. Insulating Materials, what are they made of and what is their purpose?
Hamm**d Power Soluti**s utilizes Mylar, Nomex and other high quality insulating materials. Insulati** is used to electrically insulate turn-to-turn windings, layer-to-layer windings, primary to sec**dary windings and ground.


110. What is the effect of "Overload"?
When a transformer is c**tinually overloaded, excessive heat develops and the insulati** system will begin to breakdown. As a result, the life expectancy of the transformer is shortened due to the heat exceeding the rating of the insulati** system.


111. What is a buck-boost transformer?
Buck-boost transformers are small single-phase transformers designed to lower (buck) or raise (boost) line voltage from 5-20%. The most comm** applicati**s for buck-boost transformers
Include boosting 208 volts to 230 or 240 volts for air c**diti**ing systems, boosting 110 to 120 volts and 240 to 277 volts for lighting applicati**s, heating systems and inducti** motors of all types. Many applicati**s exist where supply voltages are frequently above or below nominal.
Buck-boost transformers are c**venti**al low voltage, single-phase distributi** transformer, with standard primary voltages of 120, 240 or 480 volts, and sec**dary voltages of 12, 16, 24, 32 or 48 volts. They are available in sizes ranging from 50 VA to 10,000 VA. The primary and sec**dary are wired together to form a single-winding autotransformer. Utilizing the additive and subtractive polarity, small amounts of voltage are either added or subtracted from a distributi** circuit.


112. How does a buck-boost transformer differ from an isolating transformer?
A Buck-Boost transformer is manufactured as an isolating transformer, with separable primary and sec**dary, and is shipped from the factory in that c**figurati**. When the end user at site c**nects it, the primary is c**nected to the sec**dary changing the transformer's electrical characteristics to those of an autotransformer. This provides the smaller voltage correcti** that is typical of Buck-Boost. The primary and sec**dary windings are no l**ger isolated as they are c**nected together.


113. What is the difference between a buck-boost transformer and an autotransformer?
As noted above, when the primary and sec**dary are c**nected together to buck or boost voltage, the transformer becomes an autotransformer. If the c**necti** between the primary and sec**dary winding is not made, then the unit remains as an isolati** transformer.


114. Why are they used?
A Buck-Boost transformer is a simple and effective way of correcting off-standard voltages. Electrical and electr**ic equipment is designed to operate ****** a standard tolerance of nominal supply voltages. When the supply voltage is c**sistently too high or low - typically **** than 10%, the equipment will operate below peak efficiency.


115. Can Buck-Boost transformers be used to power low voltage circuits?
Installed as two-winding, isolati** transformers, these units can be used to power low voltage circuits including c**trol, lighting circuits, or other low voltage applicati**s that require 12, 16, 24, 32 or 48 volts output, c**sistent with the sec**dary of these designs. The unit is c**nected as an isolating transformer and the nameplate kVA rating is the transformer's capacity.


116. Why do Buck-Boost transformers have 4 windings?
A four winding buck-boost transformer with 2 primary and 2 sec**dary windings can be c**nected eight different ways to provide a multitude of voltages and kVA's. This provides the flexibility necessary for the broad variety of applicati**s. A two-winding transformer can **ly be c**nected in two different ways.


117. Will a Buck-Boost transformer stabilize voltage?
Autotransformers will not stabilize supply line voltage. The output voltage of an autotransformer is a functi** of the input voltage. If the input voltage varies, then the output voltage will also vary by the same percentage.


118. Are there any restricti**s ** the type of load that can be operated from a Buck-Boost transformer?
There are no restricti**s as to applicati** for Buck-Boost, including single or three-phase motor loads.


119. As an Autotransformer, how can a Buck-Boost transformer supply kVA power?
This is a functi** of adding voltage - a small amount of voltage is added and a small amount of corresp**ding power capacity is added as well. For example, if the transformer is c**nected in such a way that 22 volts is added to a 208 volt primary, a 230-volt output will result.
Using this example, the calculati** for autotransformer kVA is as follows:
KVA = (Output Volts x Sec**dary Amps)/1000
KVA = (230V x 41.67 Amps)/1000 = 9.58 KVA


120. How are single phase and three phase load amps and load kVA calculated?
Single phase Amps = (kVA x 1000)/Volts
Three phase Amps = (kVA x 1000)/Volts x 1.73
Single phase KVA = (Volts x Amps)/1000
Three phase KVA = (Volts x Amps x 1.73)/1000


121. Can Buck-Boost transformers be used ** 3 phase systems?
Interc**necting two or three single-phase units will readily accommodate three phase systems - refer to the corresp**ding three-phase secti** in this catalog. The number of units to be used in a 3-phase installati** depends ** the number of wires in the supply line. If the 3-phase supply is 4-wire Wye, then three Buck-Boost transformers are required. If the 3-phase supply is 3-wire Wye (neutral not available), two Buck-Boost transformers are needed.


122. Should Buck-Boost transformers be used to develop 3-phase 4 wire Wye circuits from 3-phase 3 wire Delta circuits?
No - a three-phase "Wye" buck-boost transformer c**necti** should be used **ly ** a 4-wire source of supply. A delta to Wye c**necti** does not provide adequate current capacity to accommodate unbalanced currents fl owing in the neutral wire of the 4-wire circuit.


123. Why isn't a 'closed Delta' Buck-Boost c**necti** recommended?
This c**necti** requires **** kVA power than a "Wye" or open delta c**necti**, and phase shifting occurs ** the output. The closed delta c**necti** is **** expensive and electrically inferior to other three-phase c**necti**s.


124. How do you know how to c**nect a Buck-Boost transformer?
A c**necti** chart is provided with each unit that shows how to make the corresp**ding c**necti**s. These same charts are also shown in this secti**.


125. Can 60-Hertz Buck-Boost transformers be operated ** 50-Hertz?
Due to 'saturati**' of the core, 60-Hertz Buck-Boost transformers should **ly be operated at 60 Hertz, and not 50 Hertz. Units manufactured as 50-Hertz units will however, operate at 60 Hertz.


126. Why are Buck-Boost transformers shipped from the factory c**nected as isolating transformers, and not pre-c**nected autotransformers?
The same 4-winding Buck-Boost transformer can be c**nected eight different ways to provide a multitude of voltage combinati**s. The user when assessing the supply voltage at site can best determine the correct c**necti**.


127. Why is the isolati** transformer kVA rating shown ** the nameplate instead of the autotransformer kVA rating?
Shipped as an isolating transformer, the nameplate is required to show the performance characteristics accordingly. Additi**ally, as an autotransformer, the eight different combinati**s of voltages and kava's would be impractical to list ** the nameplate. A c**necti** chart, listing the various c**necti**s, is included with each unit.


128. Do Buck-Boost transformers present a safety hazard compared to c**venti**al autotransformers?
Buck-Boost transformers **ly change voltage by a small amount, such as 208 to 240 volts. This small increase does not represent a safety hazard. C**venti**al autotransformers, manufactured as single winding transformers, change much higher magnitudes of voltage, e.g. 480 to 240 volts. In a system where the line is grounded, it is possible to have 480 volts to ground when the expectati**s are that 240 volts is at the output. For this reas**, qualified pers**nel **ly should maintain c**venti**al autotransformers.


129. How does the sound level differ between Buck-Boost and isolati** transformers?
Buck-Boost transformers, c**nected as autotransformers, will be quieter than an equivalent isolati** transformer capable of handling the same load. The isolati** transformer would have to be physically larger than the buck-boost transformer, and smaller transformers are quieter than larger **es. For example, a 10kVA is 35dB and a 75kVA is 50dB.


130. How do the costs compare between a Buck-Boost transformer and an Isolati** transformer handling the same load?
For most Buck-Boost applicati**s, the savings are about 75% compared to the use of an isolati** transformer for the same applicati**.


131. What is the life expectancy of a Buck-Boost transformer?
Buck-Boost transformers have exactly the same life expectancy as other dry type transformers.


132. Buck-Boost transformers are almost always installed as autotransformers. Does the Nati**al Electrical Code (NEC) permit the use of autotransformers?
Autotransformers are very comm** and recognized by all the safety and standard authorities. You can refer to N.E.C. Article 450-4, "Autotransformers 600 Volts, Nominal, or Less", as a reference publicati**. Item (a) details over-current protecti** for an autotransformer, and Item (b) covers an isolati** transformer being field c**nected as an autotransformer for a Buck-Boost applicati**.


133. When a Buck-Boost transformer is c**nected as an autotransformer, what is the procedure for determining the current rating of the over-current protective device, such as the fuse or circuit breaker?
The NEC Article 450-4 outlines over-current protecti** for autotransformers. It is reproduced as follows: "NEC 450-4 - Autotransformers 600 Volts, Nominal, or Less
(a) Over-current Protecti**. Each autotransformer 600 volts nominal, or less shall be protected by an individual over-current device installed in series with each ungrounded input c**ductor. Such over-current device shall be rated or set at not **** than 125 percent of the rated full load input current of the autotransformer. An over-current device shall not be installed in series with the shunt winding.
Excepti**: Where the rated input current of an auto transformer is 9 amperes or **** and 125 percent of this current does not corresp**d to a standard rating of a fuse or n**-adjustable circuit breaker; the next higher standard rating described in our secti** shall be permitted. When the rated input current is less than 9 amperes, an over-current device rated or set at not **** than 167 percent of the input current shall be permitted.
(b) Transformer Field-C**nected as an Autotransformer. A transformer field-c**nected as autotransformers shall be identified for use at elevated voltage."
Example: A 1kVA transformer, Catalog No. BKN4EA, is rated 120 x 240 to 12 x 24 volts. It is to be c**nected as an autotransformer to raise 208 to 230 volts single-phase. When c**nected as an autotransformer in this applicati**, the kVA rating is increased to 9.58 kVA, or 9,580 VA. This is the rating to be used for determining the full load input amps and the corresp**ding size of the over-current protecti** device, either a fuse or breaker.
Full load input amps = 9,580 Volt Amps = 46 Amp, 208 Volts.
When the full load current is greater than 9 amps, the over-current protecti** device - usually a fuse or n**adjustable breaker, the current rating can be up to 125 percent of the full load rating of the autotransformer input current.
Max. current rating of the over-current device = 46 amps x 125% = 57.5 amps.
The Nati**al Electrical Code, Article 450-4 (a) Excepti**, permits the use of the next higher standard ampere rating of the over-current device. This is shown in Article 240-6 of the N.E.C.
Max. size of the fuse or circuit breaker = 60 amps.


134. What is Nuisance Tripping and how can a Line Reactor eliminate it?
Transients due to switching ** the utility line and harm**ics from the drive system can cause intermittent tripping of circuit breakers. Further****, modern switchgear, equipped with solid-state trip sensing devices, is designed to react to peak current rather than RMS current. As switching transients can peak over 1000 volts, the resulting over-voltage will cause undesirable interrupti**s. A reactor added to your circuit restricts the surge current by utilizing its inductive characteristics, and therefore eliminates nuisance tripping.


135. How does a Line Reactor extend the life of switching comp**ents?
Due to the attenuati** of line disturbances, the life of your solid state devices are extended when protected by the use of a Hamm**d line reactor.


136. Will a Hamm**d Line Reactor saturate?
Due to the care in the selecti** of the core material with its optimum flux density, Hamm**d line reactors will not saturate under the most adverse line c**diti**s. Since the inductance is linear over a broader current range, equipment is protected even in extreme over-current circumstances.


137. Will a Hamm**d Line Reactor extend the life of your motor?
Line reactors, when selected for the output of your drive, will enhance the waveform and virtually eliminate failures due to output circuit faults. Subsequently, motor operating temperatures are reduced by 10 to 20 degrees and motor noise is reduced due to the removal of some of the high frequency harm**ic currents.


138. How do Hamm**d Line Reactors handle Heat Dissipati**?
Particular attenti** has been focused ** the design and field-testing of this product line. The results are reactors with ideal operating features including low temperature rises and reduced losses. Hamm**d reactors will operate efficiently and heat dissipati** in your equipment will be of minimal c**cern.


139. How does a Line Reactor minimize harm**ic Distorti**?
N**linear current waveforms c**tain harm**ic distorti**. By using a Hamm**d line reactor you can limit the inrush current to the rectifier in your drive. The peak current is reduced, the waveform is rounded and harm**ic distorti** is minimized. Current distorti** typically is reduced to 30%. Severe Harm**ic current distorti** can also cause the system voltage to distort. Often, high peak harm**ic current drawn by the drive, causes "fl at-topping" of the voltage waveform. Adding a reactor c**trols the current comp**ent, and voltage harm**ic distorti** is therefore reduced.


140. What level of Short Circuit Capability do Hamm**d Line Reactors have?
Hamm**d line reactors can withstand current under short circuit c**diti**s, reducing the potential of severe damage to electr**ic equipment. In a short circuit, the inductance of the coil is necessary to limit over-current after the core has saturated. Hamm**d has extensive experience in designing and testing dry-type transformers to withstand short circuits for the most demanding applicati**s, and this experience has been applied to line reactor design.


141. How does a Hamm**d Line Reactor reduce Line Notching?
Whenever a rectifier c**verts AC power to DC, using a n**linear device, such as an SCR, the process of commutati** occurs. The result is a notch in the voltage waveform. The number of notches is a functi** of both the number of pulses and the number of SCR's in the rectifier.
Line Reactors are used to provide the inductive reactance needed to reduce notching, which can adversely effect equipment operati**.


142. What are DV/DT Filter Reactors?
The advent of pulse width modulated (PWM) inverters with IGBT high-speed transistors, has resulted in smaller **** cost effective drives and increased switching speeds. A waveform with increased harm**ics at higher frequencies is the result of these much faster switching devices, usually at frequencies of 10,000 to 20,000 Hertz.
Drives and motors often need to be separated by significant distances. For deep wells or mines, the motors are usually c**trolled ** the surface. As a result, the distance between the drive and the motor creates l**g motor lead lengths. In some plant applicati**s, the motors can withstand the harsh envir**ment but the sensitive variable frequency drive cannot. This again results in l**g lead lengths to the motor.
Most manufactures of variable frequency drives will publish a recommended maximum distance between their equipment and the motor. Sometimes these recommendati**s create applicati** difficulties, thus increased motor lead lengths are inevitable.
DV/DT is explained as the steep-fr**t voltage pulses that travel down these l**g leads in the circuit to the motor and subsequently reverted back in a "reflective wave". When the c**ductors are l**g enough, usually 20 feet or ****, the time for reflecti** matches the time for transmissi** resulting in a high amplitude 'standing wave' ** the circuit. Voltage spikes of up to 2100 volts are frequently experienced for 600-volt systems, and motor winding failures are the result.
A Filter Reactor, installed in fr**t of the motor, combines the current limiting ability of an AC line reactor plus a resistive capacitance circuit that forms a damped, low pass filter. It provides protecti** for the motor by slowing the rate of voltage increase and minimizing the peak voltage that occurs at the motor terminals.
The cost of a DV/DT Filter Reactor is little **** than the cost of the reactor and can be mounted next to the motor, or inside the PWM enclosure.


143. What are some DV/DT applicati**s?
The Hamm**d RC series DV/DT filter reactors are specifically designed for drive/motor applicati**s with l**g lead lengths (usually where the motor cable length is 20 feet and greater). They are always installed between the IGBT variable frequency drive and the motor. Typical installati** applicati**s include producti** process lines, c**veyor systems and deep wells.


144. What is the typical "RC" DV/DT Filter Reactor performance?
The RC series DV/DT filter reactors combine appropriate values of inductance, capacitance and resistance to form a filter, which reduces DV/DT and peak voltages from the PWM voltage waveform. This combined with a 3% impedance reactor that will reduce motor heating harm**ics, will significantly increase the life of the motor.
L**g lead length motor drive applicati**s can experience motor terminal peak voltage spikes twice the DC bus voltage, and higher. Therefore motor terminal voltage peaks of 1200 volts for 480V drives and 1600 volts for 600V drives are not uncomm**. The highest peak voltages will typically occur in lower HP applicati**s.


145. What are Industrial C**trol Transformers?
A c**trol transformer is an isolati** transformer designed to provide a high degree of sec**dary voltage stability (regulati**) during a brief period of overload c**diti** (also referred to as "Inrush Current"). C**trol transformers are usually rated for 600 volts or less.


146. What is the difference between an Air Core Reactor and an Ir** Core Reactor?
Air Core:
They are used primarily as current or voltage limiting devices, particularly where large currents can enter a system that uses small amounts of power. An example is the teleph**e system, which uses very small voltages where the current in a fault c**diti** needs to be kept to a minimum.
Ir** Core:
An ir** core reactor provides the same current or voltage c**trol ** a system as its air core counterpart. Ir** core units tend to be used ** smaller applicati**s where the variables need greater or **** sensitive c**trol.


147. What are General Purpose Distributi** Transformers and where are they used?
General Purpose distributi** transformers are rated for 600 volts and below. They are generally used for supplying appliance, lighting, motorized machine and power loads from electrical distributi** systems. They are either ventilated or totally enclosed, and are available in standard ratings from 250VA up to 750kVA.


148. What are Shielded Distributi** Transformers and where are they used?
Hamm**d shielded distributi** transformers provide a copper electrostatic shield between the primary and sec**dary windings. The shield is grounded and thus shunts most noise and transients to the ground path rather than passing them through to the sec**dary. Applicati**s for shielded transformers are similar to those above, and they are ideal for commercial or electrical installati**s where electr**ic circuitry operating at low voltage DC is present and is very sensitive to 'noise'.


149. What are K-Factor Transformers and where are they used?
K-factor transformers are used as a general-purpose transformer but are designed to withstand the variety of harm**ics created in today's office and industrial envir**ments. The expanding use of devices with switch-mode power supplies and rectifier circuits with the subsequent wave distorti** requires transformers to withstand the higher harm**ics in the neutral c**ductor in the distributi** system.


150. Define K-Factor?
K-Factor is defined as a ratio between the additi**al losses created by the harm**ics and the eddy losses at the rated 60 Hz. This factor is used to specify the size of the transformer to meet the magnitude of the harm**ic load in the circuit. A standard general-purpose transformer does not have the shielding, c**ductor sizes, core cross-secti**, or the capacity in the neutral to provide the same service.


151. What is a Low Voltage General Purpose Transformer?
Hamm**d's low voltage general-purpose transformers provide a safe, l**g lasting, highly reliable power source. They are designed for general lighting and other low voltage applicati**s. They are UL listed and CSA certified.


152. What are Buck-Boost Transformers and where are they used?
Buck-Boost transformers are c**trol transformers with low voltage sec**dary windings. By field c**necting the primary and sec**dary windings in an autotransformer c**figurati**, they offer an ec**omical soluti** to the adjustment of line voltages that are slightly above or below normal.
Buck-Boost transformers can be used to adjust stable voltages **ly. Fluctuating line voltages should be regulated with a Hamm**d Voltage C**diti**er.


153. What are Autotransformers?
Autotransformers are similar to Buck-Boost transformers in that they are also an ec**omical means of adjusting an output voltage. Autotransformers are designed to adjust the supply voltage when isolati** from the line is not necessary and where local electrical codes permit. Units are designed in either a step-up or step-down applicati** and to meet motor inrush currents.


154. What are Motor Starting Autotransformers?
Motors have a large inrush current comp**ent that requires a special design. Motor starting transformers are designed to withstand an inrush of upward of 25 times normal current. They typically are tapped ** larger sizes to soft-start the motor until it is up to full RPM.


155. What are Energy Efficient (TP1) Transformers?
There is a growing movement in the electrical industry towards energy efficient products in all sectors including dry type transformers. In additi** to the benefits to the envir**ment, energy efficient transformers also can realize substantial savings in operating costs thereby having a direct impact ** the initial investment evaluated over a period of time.
The specificati**s covering energy efficiency in transformers, is the NEMA Standards Publicati**, TP-1-1996, "Guide for Determining Energy Efficiency for Distributi** Transformers". This specificati** has carefully c**sidered the total owning cost unique for industrial or commercial installati**s where the load factor is an integral part of the efficiency rating.


156. What are Low Temperature Rise Transformers?
All transformers have operating losses, and heat is the product of these losses. Hamm**d low temperature rise transformers are designed with reduced 115°C or 80°C full load operating temperature rises. These units decrease total operating losses by 20% and 35% respectively, compared with the standard 150°C rise operating system. Hamm**d low temperature rise transformers provide greater efficiency under normal operating c**diti**s, and overload capability without harm to their service life or reliability.


157. What are Encapsulated Transformers and where are they used?
These units are encapsulated and completely enclosed. The encapsulated design is especially suited for installati**s in harsh envir**ments where dust, lint, moisture and corrosive c**taminants are present. Typical applicati**s include: pulp and paper plants; steel mills; food processing plants; breweries; mines; marine and shipboard installati**s.


158. What are Medium Voltage Transformers and where are they used?
Hamm**d medium voltage transformers are really 5kV class dry type distributi** transformers. They are designed primarily for use in stepping down medium voltage power to a lower operating voltage for commercial, instituti**al or industrial applicati**s.


159. What are Drive Isolati** Transformers and where are they used?
Drive isolati** transformers are designed to supply power to AC and DC variable speed drives. The harm**ics created by SCR type drives requires careful designing to match the rated hp of each drive system. The duty cycle included is approximately **e start every 2 hours. The windings are designed for an over-current of 150% for 60 sec**ds, or 200% for 30 sec**ds.


160. What are Clean Power Products?
Computer regulators and hard-wired line voltage c**diti**ers protect equipment from both noise and voltage fluctuati**s while super isolati** transformers are all designed to provide protecti** against frequency variati** or noise related disturbances.


161. What are Power Transformers?
Hamm**d offers a wide range of dry type power transformers, rated from 750kVA up to 25 MVA. They are suitable for commercial, industrial, manufacturing or producti** process applicati**s. With three phase ratings to 46 kV class and up to 25 MVA, Hamm**d offers the latest technology and manufacturing processes available today.




162. Explain the Banking of Transformers?
Two or three, single-phase transformers can be c**nected to make a three-phase bank. The primary windings of the single-phase transformers can be c**nected in delta or Wye and the sec**dary windings can be c**nected in either a delta or Wye c**figurati**. The equivalent capacity of the bank will be equal to three times the nameplate rating of each single-phase transformer. Usually this type of installati** is **** expensive than using a single three phase transformer.


163. What are Primary Voltage Taps?
In some cases, the actual supply voltage to the primary of the transformer is either slightly higher or lower than the nameplate rating. Taps are provided ** most transformers ** the primary winding to correct this c**diti** and maintain full rated output voltage and capacity. Standard taps are usually in 2 1/2% or 5% increments. Example: The transformer has a 480V primary rating and the incoming voltage is at 504V. The primary c**necti** should be made at the +5% tap in order to maintain the nominal sec**dary voltage.


164. Can you operate a 60Hz Transformer at 50 Hz?
Transformers rated at 60Hz should not be used ** a 50Hz supply due to higher losses and core saturati**, and the resultant higher temperature rise. Transformers rated for 50Hz, however, can be operated ** a 60Hz supply.


165. Explain Balance Loading ** Single and Three Phase Transformers?
A single-phase transformer with 120/240V sec**dary has two separate 120V sec**dary windings and is usually c**nected into a 3-wire system. Care must be exercised in distributing the load ** the two 120V windings evenly, so each winding is carrying about half of the total load.
Similarly for a three-phase transformer, each phase should be c**sidered as a single-phase transformer. When distributing single-phase loads between the three phases, each of the three windings should be evenly loaded.


166. When is Sound Level an issue in the design?
Sound needs to be c**sidered when transformers are located in close proximity to occupied areas. All energized transformers emanate sound due to the alternating flux in the core. This normal sound emitted by the transformer can be a source of annoyance unless it is kept below acceptable levels. There are ways of minimizing sound emissi** as discussed in the Hamm**d "Field Service Guide". Hamm**d Transformers are built to meet the latest ANSI, CSA and UL standards. These standards are outlined in the accompanying table.


167. When can you Reverse C**nect a transformer?
In general, distributi** transformers can be reverse c**nected without de-rating the nameplate
KVA capacity. However some precauti**s need to be taken for reverse c**necti** of some smaller transformers. ** Hamm**d transformers under 6kVA three phase and 3kVA single phase, there is a "turns ratio compensati**" ** the low voltage winding.
When the input voltage, equal to the nameplate rated voltage, is c**nected to the low voltage winding, the output voltage will be slightly lower than the nameplate rating.
When a three-phase transformer is reverse c**nected thus resulting in a Wye-Delta c**figurati**, the neutral terminal must be isolated. Further, the reverse c**nected transformer may draw a higher inrush current during energizati**. Hence the sizing of the line fusing or circuit breaker may be affected.


168. Under what circumstance does need D.C. Resistance Measurement?
Current from a D.C. resistance bridge is applied to the transformers windings to determine the D.C. resistance voltage of the coils. This test is important for the calculati** of I2R for use in the winding temperature test, and as base data for future assessment in the field.


169. What is a Polarity and Phase-Relati** test for?
Polarity and phase-relati** tests are made to determine angular displacement and relative phase sequence to facilitate c**necti**s in a transformer. Determining polarity is also essential when paralleling or banking two or **** transformers.


170. Explain Voltage Ratio (turns ratio)?
To c**firm the voltage ratio of a transformer, the ratio of the number of turns in the high-voltage winding with respect to the number of turns in the low-voltage winding, is measured.


171. What are No-Load and Excitati** Current tests?
No-load losses (excitati** losses) are the core losses of a transformer that are "excited" at rated voltage and frequency, but which do not supply load. No-load losses include core loss, dielectric loss, and losses in the windings due to exciting current. The transformer is excited at rated voltage with all other windings open circuited. The exciting current and no load loss is then measured.
(Note: This is a standard test **ly ** units over 500kVA. It will **ly be carried out ** lower kVA units when specifically requested.)


172. What are Dielectric tests?
The purpose of dielectric tests is to dem**strate that the transformer has been designed and c**structed to withstand the voltages associated with specified insulati** levels.


173. What is an Applied Voltage test?
A normal power frequency such as 60hz is applied to each winding for **e minute. These tests are in accordance with table (3) in ANSI C57-12-01.


174. What is an Induced Voltage test?
The induced voltage test is applied for 7200 cycles or 60 sec**ds whichever is shorter. The voltage applied is twice the operating voltage, and c**fines the integrity of the insulati**


175. What are Impedance Voltage and Load Loss tests?
The voltage required to circulate the rated current under short-circuit c**diti**s when c**nected ** the rated voltage tap, is the impedance voltage. Rated current is circulated through the windings with the sec**dary short-circuited. The impedance voltage and load loss is measured. They are corrected to rise +20°C reference temperature. (Note: This is a standard test **ly ** units over 500kVA. It will **ly be carried out ** lower kVA units when specifically requested.)


176. What are Type Tests?
Type Tests are required either to qualify a new product or to further certify a producti** product. The following is a list of type tests performed ** Hamm**d Transformers.
Temperature Rise Test
Sound Level Test
Partial Discharge (cor**a)
Basic Impulse Insulati** Level (BIL)
Short-Circuit Test


177. What is a NEMA 1 enclosure?
This is a general-purpose ventilated enclosure for indoor use primarily designed to provide a degree of protecti** against limited amounts of falling dirt. It is ideal for normal factory envir**ments.


178. What is a NEMA 1-N enclosure?
This is a general-purpose n**-ventilated enclosure for indoor use primarily designed to provide a degree of protecti** against limited amounts of falling dirt. It is ideal for normal factory envir**ments.


179. What is a NEMA 2 enclosure?
This is a general-purpose enclosure for indoor use primarily to provide a further degree of protecti** against limited amounts of falling water (drip proof) and dirt.


180. What is a NEMA 2-S enclosure?
This enclosure is the sprinkler proof versi** of the NEMA 2.


181. What is a NEMA 3 enclosure?
This is a general purpose ventilated enclosure for outdoor use designed primarily to provide a degree of protecti** against rain, sleet, wind blown snow or dust and damage from external ice formati**. It is c**sidered ideal for c**structi** sites, subways etc.


182. What is a N**-ventilated enclosure?
A n**-ventilated enclosure is c**structed to restrict unintenti**al circulati** of external air through the enclosure.


183. What is a Ventilated enclosure?
A ventilated enclosure is c**structed to provide circulati** of external air through the enclosure to remove excess heat.


184. What is a NEMA 3R enclosure?
Similar to the NEMA 3, it is also intended for outdoor use. It provides a greater degree of protecti** against rain, sleet, falling snow or dirt and damage from external ice formati**. It is ideal for any outdoor installati** where no blowing snow or blowing c**ductive dust exists.


185. What is a NEMA 3R-E enclosure?
Although similar to the NEMA 3R it also provides added protecti** against blowing snow and dirt. It is suitable for out-door installati**s where blowing snow or blowing c**ductive dust are present.


186. What is a NEMA 4 enclosure?
NEMA 4 is a n**-ventilated indoor or outdoor enclosure designed primarily to provide a degree of protecti** against windblown dust and rain, splashing water, hose-directed water, and damage from external ice formati**.
It is suitable in areas where exposure to large amounts of water from any directi**. (Note: not submersible)


187. What is a NEMA 4X enclosure?
This enclosure is the same as the NEMA 4, and is also corrosi** resistant. It is ideal for envir**ments such as food processing plants and refineries.


188. What is a NEMA 12 enclosure?
This is a n**-ventilated indoor enclosure designed primarily for providing a degree of protecti** against circulating dust, falling dirt, and dripping n**-corrosive liquids. This enclosure is both oil and rust resistant suitable for applicati**s such as oil refineries where oil or other chemical liquids may be prevalent. (Note: not watertight)


189. Why is Clean Power so critical?
Your computer is a delicate electr**ic instrument. When you use the keyboard, you're sending a series of tiny electr**ic impulses through the computers circuits.
The computer 'reads' these electr**ic impulses and makes calculati**s or performs tasks according to your programmed instructi**s. If the electrical power feeding your computer is smooth and clean, your computer will behave normally.
However, if the power fed into your computer is "dirty", you could be in for many unpleasant surprises.


190. What is Dirty Power?
Dirty power is caused by a number of things. Simply put, dirty power is what causes your radio or teleph**e to 'crackle' during an electrical storm; or what causes 'snow' ** your TV when some**e is using a power tool, sewing machine or other appliances in your house. This dirty power, or electrical noise, is a nuisance when it appears ** your radio, TV or teleph**e. When it gets into your computer, it can cause serious errors; improper readouts, printing problems, or even damage your computers circuit.


191. How does Dirty Power affect my electr**ic equipment?
Your computer operates by reading electr**ic impulses. Dirty power c**tains a great number of random pulses riding ** the normally smooth surface of a power wave. As these random pulses enter the circuits, your computer 'reads' them as data. This can cause a whole range of problems. You may suddenly get garbled numbers or letters in a readout or printout.
You could loose files, skip program steps, have trouble loading programs or have c**necti** problems while ** the Internet.


192. How bad can the Dirty Power problem get?
**e form of dirty power usually called a surge can burn out computer, audio, video or nay other electr**ic circuitry in sec**ds. A surge is a high voltage pulse riding the normal power wave. Surges will comm**ly measure 600 to 2500 volts. Even though they occur for **ly mille-sec**ds, this is enough time to melt down circuits.


193. What are the most comm** power problems?
Research c**ducted by both IBM and Bell indicates that most line disturbances to sensitive equipment are line noise and voltage fluctuati**s.


194. What are Voltage Fluctuati**s?
Under voltages and over voltages are caused by faults ** power lines, and the subsequent acti**s of fault clearing devices. Also, by heavy loads, such as machinery start-up and by the slow reacti** of power company regulating equipment. Since computer equipment is designed to operate close to nominal voltages, the effects of these voltage variati**s can cause serious problems. Voltages can drop as much as 20% of nominal. This can result in expensive and time c**suming errors, loss of informati**, downtime, recovery and rerun costs and possible equipment damage.


195. What is electrical Noise?
Noise is a very broad term that can be applied to a number of AC power line disturbances. Lightening surges or any other sudden changes in load, such as switching motor loads or power factor correcting capacitors can produce voltage spikes and ringing. Phase c**trolled rectifier loads and arcing devices produce c**tinuous noise unless adequately filtered. Noise sources are either comm** mode, which appears between both sides of a power line and ground or of transverse mode, which appears from line to line. Hamm**d Clean Power products, such as our Computer Regulators remove these noise sources.


196. What are Harm**ics?
Harm**ics, in an electrical system, are currents created by n**-linear loads that generate n**-sinusoidal (n**-linear) current waveforms. These current and voltage wave forms operate ** frequencies that are in multiples of the fundamental 60hz frequency. That is, the fundamental frequency is at 60 hertz, the 2nd harm**ic is at 120hz frequency (60 x 2), the 3rd at 180 hertz, and so forth. Harm**ics are principally the by-product of switch-mode power supply technology where AC is rectified to DC, and back again. In the process, a capacitor is charged in the first half-cycle, and then discharged in the next half-cycle, in supplying current to the load. This cycle is repeated. This acti** of recharging causes AC current to flow **ly during a porti** of the AC voltage wave, in abrupt pulses. These abrupt pulses distort the fundamental wave shape causing distorti** to the various harm**ic frequencies.


197. What are N**-Linear Loads?
To**** n**-linear loads make up a large percentage of all electrical demand. Rectified input, switching power supplies and electr**ic lighting ballasts are the most comm** single-phase n**-linear loads. Harm**ic currents and voltages produced by single phase, n**-linear loads which are c**nected phase-to-neutral in a three phase four wire system, are third order, zero sequence harm**ics (the third harm**ic and its odd multiples - 3rd, 9th, 15th, 21st, etc., phasors displaced by zero degrees). These third order, zero sequence harm**ic currents, do not cancel but add up arithmetically ** the neutral bus, creating a primary source of excessive neutral current.


198. Explain the K-Factor rating?
K factor is defined as a ratio between the additi**al losses due to harm**ics and the eddy current losses at 60Hz. It is used to specify transformers for n**-linear loads. Transformers with a rated K factor of 4, 7, 13, 20 and 30 are available. For balanced loading, a transformer with a K factor of 4 should be specified when no **** than 50% of the total load is n**-linear. A transformer with K factor 13 should be specified when 100% of the load is n**-linear.


199. How do you choose the correct, most cost-effective Clean Power Soluti**?
Not every**e has the same power problem. Finding the most cost-effective soluti** requires some analysis of your equipment, the power system and the available soluti**s in the market. The table below lists causes and effects of many comm** power problems. You, or your electrician can determine the most likely cause of power problems based ** knowledge of your locati**, the kinds of equipment you operate in that locati**, and the kind of power distributi** system in your building. The following table lists the types of Clean Power products available from Hamm**d to solve your power problems.
POWER DISTURBANCE TYPE CAUSED BY C**DITI** EFFECT EFFECTS
Voltage Fluctuati**s
Fluctuati**s exceeding +/-5% of nominal.These can occur from millisec**ds to several sec**ds. These can occur from millisec**ds to several sec**ds. • Heavy loads being added to or removed from the power source Including: utility switching equipment, lightning suppressi** apparatus, heavy motor start-up loads such as elevators, generators, furnaces and compressors.
• Lighting loads
• Power line faults and fault clearing devices
• Brownouts • Low voltage to equipment up to 20% below normal. • Loss of Data
• Down Time
• Rerun costs
• Equipment damage
Line Noise
Fluctuati**s, transients, spikes, dips or bursts of high frequency energy, which can range from 10 to 100 times the line voltage. • Lightning
• Static discharge
• Power line faults
• Utility switch gear
• Office equipmento Disk drives
• Heavy office cleaning equipment
• Programmable c**trollers
• Printers and plotters
• Radio transmitters
• Other computers
• Fluorescent lights and dimmers
• Heater c**trols
• Motors and motor c**trols
• Power tools and appliances
• Unshielded automobile igniti** cables • Spikes or surges 600 to 6,000 volts from **e tenth to 100 milli**ths of a sec**d durati**.
• Electromagnetic Interference (EMI) or Radio Frequency Interference (RFI). • Output errors
• Character changes
• Skipped program steps
• System crash
• Memory loss
• File loss
• Misregistrati**
• Circuit damage
• 'Snow' ** video equipment and audible noise in audio equipment.
Other Disturbances • Ground not dedicated or isolated
• Shock Hazards • Electrical safety hazard • Pers**al safety hazard
• Possible equipment damage



200. What are some of the soluti**s to Dirty Power?
The soluti**s are as wide ranging as the problems. So are the prices. We have summarized some soluti**s and their price ranges in the table below.
SOLUTI** COVERAGE PRICE RANGE GENERAL USAGE
Unfiltered Surge Fuses Protect against major surges **ly. $15.00 and up • Basic protecti** against lightning strike surges - do not provide clean power.
Filtered Surge Suppressors Spikes, EMI/RFI Surges $60.00 to $300.00 • Small business, home business, home computers, audio and video.
Computer Regulators and Line Voltage C**diti**ers Spikes, surges, brownouts EMI/RFI $300.00 and up • Office computers, business applicati**s, dedicated lines, labs, test facilities
Isolati** Transformers Spikes, surges EMI/RFI $300.00 and up • Business applicati**s, dedicated services, labs, and test equipment.
U.P.S. (Uninterruptable and Power Supply) All Power problems $750.00 and up • Large main frame computers networks.


Unfiltered Surge Fuses are very inexpensive, and may provide damage protecti** from lightning strikes or other surges, but they do not filter out adverse noise.

Filtered Surge Suppressors are inexpensive soluti**s to noise suppressi** and surge protecti**. The better units inhibit surges above 5000 volts, 200 amps. They should also provide noise filtrati** of 10dB or **** to cover average power disturbances.

Computer Regulators or Line Voltage C**diti**ers protect equipment from both noise and voltage fluctuati**s. They are an inexpensive soluti**, available in both portable or hardwired models. They provide ideal protecti** in high noise areas where voltage fluctuati**s exceed the regulating range of the computers power supply.

Super Isolati** Transformers provide inexpensive protecti** against frequency variati** or noise related disturbances. This is adequate where voltage fluctuati**s are not a serious problem. Most high-end computers have built-in voltage regulati**, but still require protecti** from line noise.

U.P.S. Systems are in effect self-c**tained power centers. They provide backup power for a period of time when utility power is interrupted. Most U.P.S. systems also provide noise filtrati** and surge suppressi**.
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