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Transformer Glossary
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ANSI: ANSI was formed
in 1918. American National Standards Institute is a
recognized body which approves standards for transformers.
ANSI 89.1 is mostly used for dry type transformers.
Auto Transformer: An
auto transformer is an electrical transformer in which
the primary and secondary coils have some or all windings
in common. It uses common windings.
Air cooled Transformer: A
transformer which uses air as the cooling medium. This
may be a forced air with the use of fans.
Alternating current (ac): This
is the electricity that you get from your house's wall
and that is used to power most of your electrical appliances.
It is sinusoidal wave that starts at zero, increases
to a maximum value, and then decreases to a minimum
value, and repeats.
Ambient Noise level: The
level of acoustic noise existing at a given location
like room or compartment etc. Ambient noise level is
measured based on sound level meter or in decibels (db).
Arc voltage: The amount
of voltage present between the electrode and the work
piece. Arc voltage ranges from 17 to 45 volts. Click Me To Top
Banked: Two or more
single-phase transformers connected together to supply
a three-phase load.
BIL Basic Insulation level:
It is an insulation system that can withstand
very high voltage surges.
Breakdown voltage: also known
as Zener voltage: The voltage at which an electrical
breakdown occurs in a gas. It is also known as breakdown
potential, sparking potential or sparking voltage. Click Me To Top
Compensated Transformer: A transformer with a turn’s ratio which provides a higher than rated voltage at no load rated voltage at rated load.
Current Transformer: A current transformer is a device for measuring a current flowing through a power system and inputting the measured current to a protective relay system. A current transformer appears to be the simplest of electrical devices.
Core Loss: Core loss is also known as iron loss. Core loss is a form of energy loss that occurs in electrical transformers and other inductors. Core losses do not include the losses due to resistance in the conductors of the windings, which is often termed copper loss.
Core saturation: Condition that occurs when an inductor or transformer core has reached maximum magnetic strength.
Click Me To Top
Delta-Delta: A connection between a delta source and a delta load.
Double conversion: A UPS design in which the primary power path consists of a rectifier and inverter.
Dropout voltage: The voltage at which a device fails to operate properly or safely. Computer systems will reboot, reset, or lose data.
Delta: Delta is a three phase connection where the ends of each phase winding connection in series to form a closed loop with each phase 120 electrical degrees from the other. Click Me To Top
Electrostatic Shield: A grounded conductor sheet which is connecting primary and secondary winding to decrease or eliminate line to line or line to ground noise. It is also known as Faraday Shield.
Effective Voltage or current:The amount of power being delivered to a DC circuit load can be calculated easily by dividing the load resistance into the applied DC voltage squared.
Eddy Currents: It is induced into a metal when magnetic lines of force move across it.
Efficiency: Ratio of its power output to its total power input
Excitation Current: DC is essential to magnetize a piece of metal. Click Me To Top
FCAN Taps: Full Capacity above nominal. This is used to specify that a transformer will deliver rated KVA when connected to a voltage source which is higher than rated voltage.
FCBN (Full Capacity below Nominal) Taps: It is the same as FCAN except that the taps are below rated voltage.
Filter Press: A device for filtering and absorbing moisture from oil.
Frequency: It means the number of times an AC voltage will rotate from positive to negative and vice versa within a precise time, usually expressed in cycles per second and identified as Hz as in 60 Hz.
Faraday’s Law: A law that states an electric field is induced in any system in which a magnetic field is changing with time.
Filtered: Removing the ripple effect caused by a rectifier. Click Me To Top
Generator: A device that converts mechanical energy into electrical energy by magnetic induction.
Ground: A conducting path, whether intended or unintended, between an electric circuit or equipment and the earth or some other conductor.
Grounded: Connected to the earth or some other conductor. Click Me To Top
Horsepower (HP): One horsepower is 33,000 lb.-ft /minute.
H type core: It is one type of transformer core that surrounds the windings on four sides. This helps lessen flux leakage.
Hydroelectric: Electricity produced by turbines that are turned by water flow.
Hertz (Hz): Cycles per second Click Me To Top
Isolating Transformer: Transformer in which input windings are connected to the line and are completely isolated from those connected to the load.
Insulation: Material with high electrical resistance.
Insulator: Device used for supporting or separating conductors of electricity.
Instrument Transformer: A transformer designed to transform the conditions of current or voltage and phrase position in the primary with a specified accuracy of the secondary circuit. Click Me To Top
Jack Pads: Structural member at bottom of transformer to gather hydraulic jacks which lift onto rollers for moving into position. Click Me To Top
Kilowatt (KW) 1,000 Watts
KWH: Kilowatt hour, one kilowatt for one hour.
KVA: Kilovolt-ampere, or thousand volt-ampere. When multiplied by the power factor, will give kilowatts, or KW.
K-Factor: this is used to point out a full rated transformer which is specifically designed to handle non-linear loads. Numerical values taking into account both the magnitude and frequency of any component of a current waveform. Click Me To Top
Linear Load: A load in which the relationship between current and voltage is directly proportional. For example: water heater, resistance heating etc.
Line voltage: Voltage of a power line
Lamination: The sheets of steel making up the core of the transformer. Click Me To Top
Magnetic Shielding: Conductive material placed around a transformer’s coils to attenuate stray magnetic fields.
Multiple Winding: A winding which consists of two or more sections that can be paralleled to specific mode of operation. Click Me To Top
Network Transformer: Transformer which is electrically and mechanically connected to and coordinated in design with switch-gear or motor control assemblies for use on a utility network power system.
NEMA Standard: Any standard recommended by the National Electrical manufacturers Association.
Non-Ventilated Construction: The core and coil assembly is mounted inside an enclosure which has no ventilation openings.
Non Linear Load: A load in which the relationship between current and voltage is not directly proportional. Click Me To Top
Overload: When a transformer is overloaded, too much heat is developed, and insulation system begins to break down out of proportion to the amount of overload. Life expectancy decreases due to over heating which results in break down of insulation system.
Open Frame: A method of transformer construction utilized when the transformer will be combined with other components inside an enclosure.
Oscillation: The variation, usually with time, of the magnitude of quantity with respect to a specified reference when the magnitude is alternately greater and smaller than the reference. Click Me To Top
Primary winding: The coil winding that is directly connected to the input power.
Power Factor: Watts divided by volt amps, Kw divided by KVA
Peak voltage: Current voltage that reaches its maximum or peak level. This occurs twice and lasts for only a fraction of the cycle. Direct current voltage is peak voltage at all times.
Phase: Circuits have single-phase, three and four phase. Usually circuits are rated single-phase three wires or four wires. Single-phase transformers can be used on a three-phase source when tow wires of the three-phase system are connected to the primary of the single-phase transformer. Click Me To Top
Rated Power: Expressed in volt-amperes (VA) or Kilovolt amperes (KVA).
Rectifier: An electrical device used to change AC power into DC power.
Regulation: The percentage difference between a secondary winding’s output voltage when operating under n0-load or open-circuit and full load conditions.
Resin Filled Construction: The core and coil assembly is completely encapsulated with a resin-sand compound and contained in a metal enclosure. Click Me To Top
Short circuit: A low resistance connection, usually accidental, across part of a circuit, resulting in excessive current flow.
Sinusoidal: Having the form of a sine wave.
Step up/step-down transformers: A step-up transformer is one in which the output voltage is greater than input voltage. In a step-down transformer, the input voltage is greater than the output voltage. Click Me To Top
Taps: Incoming plant voltage varies according to the distance from the substation and other factors. Taps allow a distribution transformer to provide secondary voltage as close as possible to the desired operating voltage.
T-connection: A Scott connected three-phase transformer utilizing two primary and two secondary coils called the main and teaser coils.
Transformer Regulation: The percentage difference between voltage at the secondary terminals under no-load condition versus voltage under full-load. This value depends on the load power factor and is usually reported at 1.0 PF and 0.8 PF.
Three phase Power: Three separate outputs from a single source with a phase differential of 120 electrial degrees between any two adjacent voltages or currents.
Transient: A high amplitude, short duration pulse superimposed on the normal voltage wave form or ground line. Click Me To Top
Ventilated: Providing circulation of external air.
Ventilated Enclosure: Ventilated Enclosure allows air to flow directly over the core and coil assembly for cooling.
Volt-Amperes: Transformers are related in volt-amperes (the product of volts and amperes in the input winding). Capacities of very large transformers are rated in thousands of volt-amperes and in millions of volt-amperes. Input KVA is equal to output KVA. Click Me To Top
Watt: Unit of electrical power when the current in the circuit is one ampere and the voltage is one volt.
Weather shield: When added to ventilated enclosures, allow indoor-rated units to be situated outdoors, changing the enclosure rating to NEMA 3R. Click Me To Top
Zig-Zag Transformer: A transformer where the windings are physically manipulated to achieve certain voltage and current phase relationships. A zig-zag winding arrangement is commonly found in harmonic mitigating or grounding styles of transformers.
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