Electric Transformers Types and Terms

Electric Transformer Types

  • Current transformers have a primary winding linked in with the circuit to transform the current to measurable medium.
  • Distribution transformers are rated between 3 and 500 KVA with 601 volts or more.
  • Dry type transformers do not use liquid to cool or insulate.
  • High resistance transformers have high leakage to reactance to limit the output current to a designated value in the event of a fault.
  • High voltage transformers are designed to handle electrical energy in high voltage levels.
  • Instrument transformers accurately measure and monitor power voltage as it is transmitted proportionally through the primary and secondary coils.
  • Inverters convert between AC and DC power.
  • Isolation transformers are transformers that insulate the primary circuit from the secondary circuit.
  • Low voltage transformers convert into lower voltages.
  • Power transformers are devices that convert voltage to lower levels.
  • Pulse transformers are wide-band devices that are mainly intended for waveform transmission, which transmit rectangular electrical pulses, meaning that the pulses have fast rise and fall times with a fairly constant amplitude.
  • Step down transformers have the power to convert higher voltages to lower voltages by means of transferring electrical energy through two coil stages, the second coil stage having fewer coil windings.
  • Step up transformers are transformers that have a high voltage winding connected to the output load and a low voltage winding connected to the power source.
  • Toroidal transformers have copper wire around a cylindrical core so the magnetic flux is contained.
  • Transformers are a static piece of apparatus that transfers electrical energy from one circuit to another circuit by electro-magnetic induction, often with altered values of voltage and current.

Electric Transformer Terms

Air Cooled - A transformer which uses air to cool by use of fans or normal ventilation.

Auto Transformer - A transformer with one winding per phase.

Banked - Describes multiple single phase transformers connected together to provide power to a three phase load.

Core - The transformer's central part or inductor that enhances the power of the magnetic field.
 
Core Saturation - A condition that results from a transformer or inductor reaching highest magnetic strength.

Delta - In a three phase connection the windings all connect to form a loop.

Duty Cycle - proportion of time for a transformer to provide full rated power to the load. This measurement greatly affects the actual size of the transformer.
 
Electrostatic Shielding - A component that sits between windings -typically the primary and secondary - to supply the most isolation; more of these can be placed between secondary windings as needed; it is normal to connect the shielding to the core. Encapsulated - a dry transformer with an enclosed core and coil assemble.

Exciting Current - The amount of current a transformer draws at nominal voltage input in an unloaded state.
 
Ferroresonance - Resonance results from the saturation of a ferrous core of an inductive component, which increases the inductive reactance relative to the capacitance reactance.
 
Filter - A complex system within the transformer that consists of capacitors, inductors, and a resistor; it provides a relative small opposition to specific frequencies or direct current, as it blocks or attenuates other frequencies.

Flexible Connector - A conductor that can handle thermal expansion and contraction as well as reduce noise.

Impedance - That the forces that resist the flow of current in AC circuits like resistance or inductive or capacitive reactance.
 
Inductance - The capability of a coil for storing energy and resisting changes in the flow of current; it is a function of the core material, amount of turns of the coil and the cross section.
 
Inrush Current - This is when the transformer has a short current surge through it, from residual flux, occurring at the moment energy is applied to the transformer.
 
Isolation Transformer - This transformer has physical separation from the primary and secondary windings in order to allow magnetic coupling between isolated circuits and minimize electrostatic coupling.

KVA - Kilovolt Ampere rating that is a measurement of the output of a transformer without exceeding a certain temperature.

Load - The quantity of electric power supplied or necessitated at any particular spot in the system. Also a requirement of the KVA or VA from the transformer; light bulbs are loads.
 
Magnetic Shielding
- This conductive material attenuates stray magnetic fields by its positioning around a transformer's coils.

Polarity - The direction of the current between two leads. If the directions are the same then the leads have the same polarity. In electric transformers the polarity is classes as either additive or subtractive.

Power Factor - Watts divided by volt amps, KW divided by KVA. Power factor: leading and lagging of voltage versus current caused by inductive or capacitive loads, and harmonic power factor: from nonlinear current.
 
Rated Power - The total of the Volts and Amps derived from all the secondary windings.
 
Reactance - This is the opposition to variations of alternating current, capacitive reactance is in terms of capacitors, and inductive reactance is the opposition to change from an inductor or coils.
 
Resonance - A condition of an AC circuit in which capacitive and inductive reactances interact, resulting in a maximum or minimum circuit impedance.

Secondary Winding - On the load or output side, the connected transformer winding.

Sudden Pressure Relay - Pressure switch device which detaches the transformer from the line.

Voltage - The measurement of the amount of force on a unit charge because of the surrounding charges.

Voltage Regulation - The change, in percentages, of the output voltage from no load to full load.
 
Voltage Taps - Supplemental connections to a winding which permit varying voltages from the same winding; typically utilized on the primary winding to permit the transformer to be used in different countries with varying line voltages.