21/08/2017

In this post, function, structure, effect of frequency on output pulse, advantages and disadvantages of pulse transformer is discussed.

Pulse Transformer

Function of Pulse Transformer

The function of pulse transformer is to generate pulse for semi conductor device and provide electrical isolation.

The figure A shows toroidal shaped pulse transformer.
It consists of one primary winding and one secondary winding.
Each winding consists of same number of turns therefore any winding works as primary or secondary winding.
The pulse to SCR is given by 1:1 or 1:1:1 pulse transformer.
The pulse to the back to back SCR is given by the three winding pulse transformer.
The firing circuit of gate pulse by 1:1 pulse transformer is given in the figure B.
The function of the series resistor R is to limit the holding current of the SCR.
The function of diode D is to prevent reversing gate current. The 1:1:1 pulse transformer is used to generate pulse for back to back SCR.

The design of Pulse transformer is made such that

Its efficiency should be high.
The inductance of primary winding should be high in order to reduce magnetizing current.
The direct current flows through primary winding of pulse transformer in order to prevent saturation of the core.
There must be insulation between winding in order to protect winding from saturation.
Tight coupling between primary and secondary winding must be necessary.
The stray signal provides path through inter phase capacitance at high frequency.

The frequency and shape of the output pulse and input pulse same for high pulse frequency.
The output is directly proportional to integration of input at low pulse frequency.

Small size

Low cost

It can operate at high frequency.

High isolation voltage

The secondary waveform should be different from primary waveform at low frequency.

The DC current flows through primary winding in order to reduce saturation of the core.

Power electronics

Communication

Digital electronics

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