Test: Cyclo Converters - Electrical Engineering (EE) MCQ

Speed of induction machines can be controlled by controlling the input frequency. In induction heating, eddy current is proportional to the square of input frequency.

Given,
V_out(rms)= 240 V
m = 3 (for 3 phase)
We know that the fumdamental value of rms output voltage is given by




= 290 V

The basic principle of three phase cycloconverter is to vary progressively the firing angle of the controlling devices.

During the conversion process, the current flows in both the directions, hence both inverting and converting action takes place.

A cycloconverter converters input power at one frequency to output power at a different frequency with one-stage conversion.

Cycloconverters are mainly used where precise speed control is needed. It means cycloconverter is not suitable for cement mill drive as well as compressor drive. Papermill requires constant speed drive. So cycloconverter fed induction motor drive is widely used for machine tool drive.

In the positive half cycle, upper terminal is positive of the upper secondary and the lower terminal is negative for the lower secondary. Hence, P1 and N2 are forward biased.

Pairs P1, P2 and N1, N2 are forward biased from ωt = 0 to π.

Reduction factor = output frequency/input frequency.

In the positive half cycle, upper terminal is positive of the upper secondary and the lower terminal is negative for the lower secondary. Hence, P1 and N2 are forward biased. And likewise, N1 and P2 will conduct in the next half cycle.