Transformer Terms

This is a list of transformers terms that may be  used in the industry or terms you might see in articles about transformers.

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

Alternating Current - An electrical current flow of continuously changing polarity, which rises to a maximum voltage in one direction, decreases to zero and then sinks to the maximum voltage in the other direction before changing polarity once again. This pattern is referred to as a sinusoidal wave and the number of cycles per second is equal to the frequency, which is measured in "Hertz".

Ambient Temperature - The normal surrounding temperature of the environment in which a transformer will operate.

Banked - Describes multiples single phase transformers connected together to provide power to 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.

Current Transformer - A transformer used in instrumentation to assist in measuring current. It utilizes the strength of the magnetic field around the conductor to form an induced current that can then be applied across a resistance to form a proportional voltage.

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

Delta-Delta - The connection between a delta source and a delta load.

Delta-Wye - The connection between a delta source and wye load.

Duty Cycle - Proportion of time for a transformer to provide full rated power to the load. This measurement reatly 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.

Faraday Shield - A grounded metallic barrier that can be used for improved isolation between the windings of a transformer. In this application, the shield basically reduces the leakage capacitance between the primary and secondary.

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.

Flux - The lines of force of a magnetic field.

Ground Fault - Any undesirable current path from a current carrying conductor to ground.

Ground Fault Interrupter - A device whose function is to interrupt the electric circuit to the load when a fault current to ground exceeds a predetermined value that is less than that required to operate the over-current protective device of the supply circuit.

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.

Inverter - A device used to change DC into AC power.

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

Linear Load - A load in which the relationship between current and voltage is directly proportional.

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 it positioning around a transformer's coils.

NEMA Enclosure - (National Electrical Manufacturers Association) An enclosure conforming to NEMA specifications, usually constructed of metal, that provides some measure of protection against weather and other elements. Different NEMA ratings determine the degree of protection, ranging from "some measure of protection" to "fully weatherproof". Suitable for outdoor use or where indoor location may constitute a shock hazard if connections are left exposed. 

Nominal Voltage - The normal or designed voltage level. For three phase wye systems, nominal voltages are 480/277 and 208/120 where the first number expresses phase to phase (or line to line) voltages and the second number is the phase to neutral voltage. The nominal voltage for most single-phase systems is 240/120.

Nonlinear load - A load in which the relationship between current and voltage is not directly proportional.

Ohm's Law - The relationship between voltage (pressure), current (electron flow), and resistance. The current in an electrical circuit is directly proportional to the voltage and inversely proportional to the resistance. E=lR, or l=E/R, or R=E/l. Where E=voltage, l-current, and R=resistance.

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.

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.

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 no-load or open-circuit and full load conditions.

Resonance - A condition of an AC circuit in which capacitive and inductive reactance's interact, resulting in a maximum or minimum circuit.

Shielding - Imposing a metallic barrier to reduce the coupling of undesirable electromagnetic signals.

Sinusoidal Waveform - A waveform that can be expressed mathematically by using the sine function.

Taps or Voltage Taps - Additional connections to a winding allowing different voltages to be obtained from the same winding. Often used on the primary winding to allow the transformer to be used in different countries having different line voltages available.

Transient - A high amplitude, short duration pulse superimposed on the normal voltage wave form or ground line.

Voltage Regulation - Maintaining stability of output voltage under conditions of fluctuating input voltage.

Wye - A wye connection refers to a polyphase electrical supply where the source transformer has the conductors connected to the terminals in a physical arrangement resembling a Y. Each point of the Y represents the connection of a hot conductor. The angular displacement between each point of the Y is 120 degrees. The center point is the common return point for the neutral conductor.

 Power Transformer Information:

 Power Transformer Manufacturer

• ACME Transformers - With Acme Electric being in business over 80 years, they have always believed in offering there customers superior service, quality and technical expertise in the transformer market.
• AMVECO Transformers - AMVECO designs and manufactures toroids transformers, current transformers, and auto transformers. Most AMVECO products are custom designed utilizing their state-of-art proprietary CAD programs.  The AMVECO engineers can quickly generate designs in a matter of hours, if needed.
• Federal Pacific Transformers -  Federal Pacific is a division of Electro- Mechanical Corporation, a privately held, American owned company founded in 1958. Federal pacific offers dry-type transformers from .050 KVA through 10,000 KVA single and three phase, up to 34.5 KV, 150 KV BIL with UL approval through 15 KV.
• Marcus Transformer - Ever since they opened their doors for business a half a century ago, they have been a leader in innovative transformer design. As a family-owned company they are proud of the reputation they have earned for making quality-built transformers that deliver exceptional performance and savings.
• Hammond Transformers -  Hammond Manufacturing was founded in 1917 in Guelph, Ontario, Canada. In the last 3 decades it has expanded to the US and the international markets offering many types of power transformers. 
• TEMCo Transformers   TEMCo  a family-owned business has been manufacturing and distributing electrical products since 1968. They  focus on transformers that significantly reduce power consumption over 30 percent compared to competitive makes.
• GE Transformers - GE has been a key player in the energy industry for more than a century.  Since the installation of their first steam turbine in 1901. They have become number one provider of high-technology power generation equipment.
• Jefferson Electric Transformers - Jefferson Electric has been a pioneer and innovator of magnetic products since 1915. Jefferson broad line of dry-type transformers are backed by quality assurance systems so stringent that each and every unit gets thoroughly tested before it goes out there door.
• More power transformer brands - Check out more companies by clinking this link.

 Power Transformer Types

• Distribution Transformers - Distribution Transformers are generally used in electrical power distribution and transmission power. This class of transformer has the highest power, or volt-ampere ratings. and the highest continuous  voltage rating.
• Substation Transformers - Substation transformers are large devices which usually weigh tens of thousands of pounds.   They are filled with tens of thousands of gallons of heat transfer fluid.  Although they are typically 99.8% efficient in the transforming of electricity from one voltage to another, processing hundreds of Mega Volts-Amps of electricity force the liberation of hundreds of BTUs per second.
• Medical Grade Isolation
   Transformer - Medical Grade Transformers generally refer to the transformers used in medical devices as well as hospital, biomedical and patient care equipment. There are a number of strict safety rules, guidelines and laws governing the design, construction and the test of these transformers.
• Drive Isolation Transformer - They are used to adjust the speed of induction motors by varying the frequency. They are becoming more popular because of their impact on energy saving, and they are easy to control.
• Toroidal Transformers - Toroidal transformers are more efficient than the cheaper laminated EI types of similar power level. Some of the advantages are smaller size, lower weight, less mechanical hum, (making them superior in audio amplifier), low-off-load loss.

 Power Transformer Types

• Step-Up Transformers - A Step-Up Transformer is one whose secondary voltage is greater than its primary voltage.  This kind of transformer "steps up" the voltage applied to it. -
• Step-Down Transformers - A Step-Down Transformer is  designed to reduce voltage from primary to secondary.  They can range from sizes from .05 kva to 500 kva
• Isolation Transformers - An isolation transformer is a device that transfers energy from the alternating current (AC) supply to an electrical or electronic load.  It isolates the windings to prevent transmitting certain types of harmonics.
• Buck Boost Transformers - Buck Boost Transformers make small adjustments to the incoming voltage. They are often used to change voltage from 208v to 240v for lighting applications.  One major advantages of Buck boost transformers are their low cost, compact size and light weight. 
• High Voltage Transformer - There are many different types of voltage transformers. A high voltage transformer operates with high voltages. Typically, these voltage transformers are used in power transmission applications, where voltages are high enough to present a safety hazard.
• Medium Voltage Transformers - A medium voltage transformer can be connected directly to a primary distribution circuit and generally has the most load diversity. These voltage transformers have installation practices that are generally in accordance with application recommendations from the Institute of Electrical and Electronic Engineers (IEEE).
• Low Voltage Transformers - A low voltage transformer is an electrical device that transforms 120 volts (line voltage) into 12 volts or 24 volts (low voltage). Some uses for low voltage transformer are in landscaping lighting.
• Single Phase Transformers - In electrical engineering, single-phase electric power refers to the distribution of electric power using a system in which all the voltages of the supply vary in unison. Single-phase distribution is used when loads are mostly lighting and heating, with few large electric motors.
• Three Phase Transformers - Three Phase Transformers must have 3 coils or windings connected in the proper sequence in order to match the incoming power and therefore transform the power company voltage to the level of voltage needed while maintaining the proper phasing or polarity.
• Custom Transformers - Custom transformers are designed for a certain performance specifications and size requirements.  The company works with your engineering specification. 
• Industrial Control Transformers - Industrial Control Transformers are used to convert the available supply voltage to the required voltage to supply industrial control circuits and motor control loads.
• Pad Mounted Transformers - Pad Mounted Transformers are usually single phase or three phase and is used where safety is a main concern. Typical Application is restaurant, commercial building, shopping mall, institutional. 
• Pole Mounted Transformers - Pole Mounted Transformers are used for distribution in areas with overhead primary lines. Outside a typical house one can see one of these devices mounted on the top of an electrical pole.
• Oil Filled Transformers - Oil-filled transformers are transformers that use insulating oil as insulating materials.  The oil helps cool the transformer. Because it also provides part of the electrical insulation between internal live parts, transformer oil must remain stable at high temperatures over an extended period.
• Dry Type Transformers - Dry-type transformers are available for voltages up through 34.5 kV (although the most common upper limit is 15) and kVA ratings up through 10,000 (with 5000 as the usual limit). Dry-type use air as a coolant, lowering health and environmentally concerns.
• Auto Transformers - An autotransformer is an electrical transformer with only one winding. The winding has at least three electrical connection points called taps. Autotransformers are frequently used in power applications to interconnect systems operating at different voltage classes, for example 138 kV to 66 kV for transmission. Another application is in industry to adapt machinery built for 480 V supplies to operate on the local 600 V supply.
• More power transformer types - Read further about additional transformer types and their uses.

 Power Transformer Term Definitions

• Electrical Transformers - electrical transformers are devices used to raise or lower the voltage of alternating current. For instance, power is transported over long distance in high voltage power lines and then transformers lower the voltage so that the power can be used by household.
• Isolating Transformers - Isolating transformer   is a transformer, often with symmetrical windings, which is used to decouple two circuits.  An Isolation transformer allows an AC signal or power to be taken from one device and fed into another without electrically connecting the two circuits. Isolation transformers block transmission of DC signals from one circuit to the other, but allow AC signals to pass. 
• Transmission Power Lines - A transmission line is the material medium or structure that forms all or part of a path from one place to another for directing the transmission of energy, such as electromagnetic  or acoustic waves as well as electric power transmission. Components of transmission lines include wires, coaxial cables,  dielectric slabs, option fibers,  electric power lines, and waveguides.
• Transformer Voltage - The measure of the amount of force on a unit charge because of the surrounding charge.
• Transformer Phase - Most transformer are either single phase or three phase.
• Transformer Frequency - The transformer cannot change the frequency of the supply. If the supply is 60 hertz, the output will also be 60 hertz.
• Transformer K Factor - Some transformers are now being offered with a k-factor rating. This measure the transformer's ability to withstand the heating effects of non-sinusoidal harmonic currents produced by much of today's electronic equipment and certain electrical equipment.
• Primary Voltage -The coil winding that is directly connected to the input power.
• Secondary Voltage -The coil winding  supplying the output voltage.
• Harmonic Cancellation -
  Harmonic cancellation is performed with harmonic canceling transformers also known as phase-shifting transformers. A harmonic canceling transformer is a relatively new power quality product for mitigating harmonic problems in electrical distribution systems. This type of transformer has patented built-in electromagnetic technology designed to remove high neutral current and the most harmful harmonics from the 3rd through 21st.
• Weatherproof - Enclosed transformers come with a weatherproof standard set by NEMA.
• Epoxy Encapsulated - A process in which a transformer or one of its components is completely sealed with epoxy or a similar material. This process is normally preferred when a unit might encounter harsh environmental conditions.
• More power transformer terms -Such as inductor, ground fault, core saturation, current transformer, faraday shield.

Related Transformer Products

• Voltage Regulators - A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level.
  It may use an electromechanical mechanism, or passive or active electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages.
• AC Line Reactor - AC Line Reactors is a three phase transformer used in conjunction with AC variable frequency and DC motor drive. They are a bi-directional protective filtering device.
• Line Power Conditioners - Power or line conditioners regulate, filter, and suppress noise in AC power for sensitive computer and other solid state equipment.
• DC Power Supplies - Conversion of one form of electrical power to another desired form and voltage. This typically involves converting 120 or 240 volt AC supplied by a utility company   to a well-regulated lower voltage DC for electronic devices.
• Rotary Phase Converters - Rotary phase converters are most commonly used in home or small commercial or industrial settings. Rotary phase converters convert single-phase power into three-phase power. This is a very cost-effective way to power three-phase electric motors
• Frequency Converters - A frequency changer or frequency converter is an electronic device that converts alternating current (AC) of one frequency to alternating current of another frequency.
• Voltage Converters - A voltage converter changes the voltage of an electrical power source and is usually combined with other components to create a power supply.
• Magnetic Motor Starters - Magnetic Motor starters are essentially heavy duty relays mounted in boxes, often equipped with heater/thermal overloads matched to the motor they start.
• Motor Starting Auto Transformers - An Auto transformer starter uses an auto transformer to reduce the voltage applied to a motor during start. The auto transformer may have a number of output taps and be set-up to provide a single stage starter, or a multistage starter.

For an additional resource the Best of Industry Web Directory : Electrical Power Transformer Directory section is quite useful.