General Transformer Information

Why are transformers required?

The transformer's main purpose is to change one form of voltage to another, making it possible to operate a great variety of loads at their suitable voltages. The coils are usually wound on a core of laminated electrical steel or ferrite magnetic material. Below are just a few of the different styles of transformers used in the induction-heating industry.

Sizing and Specifying Transformers

To properly size or specify a transformer the following information is generally required: the input voltage to the transformer, kW of the power source, the frequency range of the power source and the frequency range at which the transformer will operate, the turns ratio or the output voltage required at full load (or no load), the input kVA at the minimum and maximum turns ratio, expected efficiency (based on the kW rating of the power source) or the kW loss of the transformer. It is also helpful to know any unique characteristics of the power source, type of waveform, or if any DC will be present. The more information the designer has available, the more assurance the customer has of getting the proper and most efficient transformer.

Transformer Maintenance

As a general rule, when transformers are water-cooled, most of the failures occur because of a breakdown of the insulation between the windings. Normally this is due to lack of water, poor quality water, water-inlet temperature being too high, or operating the transformer outside of its designed rating. Insulation failure is sometimes caused by the harsh environment the transformer is subjected to. Another failure that commonly occurs would be the melting of the output connection (fishtail), which is caused by improper tightening (recommended torque is 30 to 40 ft/lb.), or maintenance on the inductor, which includes dirty and oxidized surfaces on the mating inductor or Fishtail surface. There are occurrences when the core fails. Again, this may be due to the lack of water, poor quality water, the input volts per turn are too high (exceeds core loss temperature limitation), and improper use of frequency. One of the best investments you can make is in a well-designed water system. This will pay for itself with reduced component failures and reduction of downtime. Proper maintenance at the inductor and transformer connections will also help greatly.

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