A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors — the transformer's coils or "windings". Except for air-core transformers, the conductors are commonly wound around a single iron-rich core, or around separate but magnetically-coupled cores. A varying current in the input or "primary" winding creates a varying magnetic field in the core(s) of the transformer. This varying magnetic field induces a varying electromotive force or "voltage" in the output or "secondary" winding. If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will flow from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding is in proportion to the primary voltage, and is given by the ratio of the number of turns in the secondary to the number of turns in the primary.

An isolation transformer does not have a direct electrical path from the input side to the output side. Although any transformer with a separate primary and secondary winding can be called an isolation transformer, the term is usually used to denote a transformer built just for that purpose. These transformers are used to reduce the risk of electric shock hazard, and may have equal input and output voltages, and are therefore used strictly for the safety isolation they provide.

An auto transformer has only a single winding with two end terminals, plus a third at an intermediate tap point. The primary voltage is applied across two of the terminals, and the secondary voltage taken from one of these and the third terminal. The primary and secondary circuits therefore have a number of windings turns in common. This often allows the transformer to be slightly smaller, less costly, and often more efficient, than the isolation transformer counterpart of the same power rating, but it lacks the safety of an isolation transformer.

Yes. “Line frequency” transformers are designed for use at 50 Hz and/or 60 Hz, but “high frequency” transformers are designed to operate at higher frequencies – kHz, MHz, and beyond. High frequency transformers can be made smaller than their 60Hz counterparts of the same power level, but they introduce electromagnetic interference (EMI) considerations that are largely be ignored at lower frequencies.

Regulation compares the difference in output voltage WITHOUT the load current applied to the output voltage WITH the load current applied. It is usually expressed as a percentage change. The higher the transformer’s efficiency, the less the voltage will change. Therefore, “better” regulation means less change in voltage, and therefore a lower percentage value.

A ferrite core transformer is required if the operating frequency is in the kHz or MHz range.

Simply stated, a toroid transformer is one that uses a toroid, or doughnut-shaped, core. Toroid cores may be made from long wound strips of steel for low frequency transformers, or made of ferrite materials for high frequency transformers. The round shape of a toroid core means there are no gaps, or breaks, in the magnetic flux line path, and therefore fewer magnetic losses. This is a distinct advantage in certain applications. The toroid cores themselves, as well as the specialized winding and assembly methods often render toroid transformers slightly more costly than other types.

A ferrite core transformer is required if the operating frequency is in the kHz or MHz range.

Certainly, as long as the combination of the ambient temperature and the temperature generated by the transformer itself does not exceed the applicable temperature limits. The limits may be set by regulatory standards, or, in the absence of such standards, simply by the temperature ratings of the insulating materials.

Duty cycle, in simplistic terms, is the percentage of time a transformer is active, or energized and loaded according to its ratings. If it is always “on”, then it is said to have a 100% duty cycle, or rated for “continuous duty”. Average, effective, or equivalent duty cycle must be calculated for transformers whose loads vary over the course of a typical cycle.

Typically, the most costly components in a transformer are the magnetic core material and the copper wire or foil. On occasion, specialized insulation materials (high voltage and/or high temperature) and protective devices (fuses, circuit breakers, thermal cutoffs, etc.) can also add substantial cost.

It is difficult, and arguably reckless, to make a blanket statement of what the minimum safety requirements should be for transformers. Requirements vary depending on voltage and power levels, the regulatory standards for the specific applications, and in which global markets the transformers will be used.

There are many standards for medical/dental applications, but most use one or more sections of UL/EN 60601-1.

There are typically two (2) options: • The transformer manufacturer submits the transformer to the applicable safety agencies for component approval(s), or, • The end product manufacturer submits the transformer for investigation along with the end product. In this case, the transformer manufacturer provides the end product manufacturer with the requisite transformer documentation needed by the investigating agency.

Limited air density, due to increased altitude can have an effect on the operation performance of low-voltage components. For applications at high altitude, some studies have been performed, (Study by Subhas Sarkar and John K. John) but not much is known about this effect on the operation performance of these components. Characteristics such as dielectric voltage withstand, thermal current carrying capacity, overload calibration, contact life, and interruption capability can be affected by the decreased air density. Standard - A transformer may be used at full nameplate capacity up to 3300 feet (1000 meters). Above that altitude, the capacity of the transformer should be derated by 0.3% for each 300 feet of elevation above 3300 feet. (Per IEC 726/ANSI C57.12)

A control transformer is designed to provide rated output voltage at full VA. As the load goes down, the output voltage will go up. Conversely, increased load current will result in lower output voltages. Typically, the smaller the VA size transformer, the greater difference there is between no-load and full-load voltage.

Temperature class = The transformer insulation system The standard insulation system classification, are as follows: 105(A), 130(B), 155(F), 180(H), 200(N), and 220(R).

Temperature rise is the difference between the average temperature of the transformer windings and the ambient temperature.

Definition - Class 2 transformer: A transformer that has 30 volt rms [root mean squared] maximum secondary potential under any condition of loading. The portion of the wiring system between the load side of a Class 2 power source and the connected equipment. A Class 2 power source is limited to the following ratings:

NOT used for - Power supplies, toy transformer, cord or plug connected, direct plug-in, for audio, television type appliances, or other special types of transformer covered in requirements for electrical devices or appliances. Used in Class 2 circuits that need to comply with ANSI / NFPA 70, or the Canadian Electrical code part 1, CSA C22.1, connected to sinusoidal sources. The application / end product dictate which category of transformer may be used. The safe use of transformers is critically dependent on the electrical system they are installed into. The investigation to assess safety of the system and components, is for system compatibility.

Intended to be used in the US, Class 3 circuits that need to comply with ANSI / NFPA 70, connected to sinusoidal sources and limited to 100V, loaded or unloaded. The portion of the wiring system between the load side of a Class 3 power source and the connected equipment. A Class 3 power source is inherently limited to between 31 and 100 volts at 100 watts, and non-inherently limited to between 31 and 150 volts at 100 watts. Like a Class 2 circuit, it can be installed without a conduit; however, because has higher voltage and power limits than a Class 2 circuit, the NEC has additional requirements for safety.

(DFM) is the general engineering principle of designing products in such a way that they are easy to manufacture to insure fit and function.

A control transformer is an isolation transformer designed to provide a high degree of secondary regulation during inrush current .

Control transformer can be reverse connected. However the output voltage will be less than it’s rating because number of turns in winding.

Three single phase transformers can be connected to form a three phase bank, their primary and secondary windings are connected in WYE or DELTA connection.

Hot spot is the highest temperature inside the transformer coil.

Potting will help the transformer from moisture, dust, dirt and other contamination, It also run cooler than a non-potted unit.

The insulation system is based on various material used in group use in designing. It provides a comparable life expectancy. The choice of insulation system depends on application and cost.

Transformer is needed to step down or step up the voltage from input source. It also provide output voltage stability for short period when overload inrush occurred.

No control transformers are not current limiting It allow all the current required by the load.

Control transformer does not regulate the output voltage but variations in input voltage will reflected the output voltage proportionately.

It protect the transformer coil from industrial contamination, and moisture. It also make transformer runs cooler under loaded condition.

Transformer is not power conditioning product however it will provide some degree of clean up of electrical noise, spikes, surges and transients.