A chopper circuit is operating on TRC control mode at a frequency of 2 kHz on a 230 V dc supply. For output voltage of 170 V, the conduction and blocking periods of a thyristor in each cycle are respectively

Concept:

In TRC (time ratio control) method, the ON period of the switch (TON) is varied by keeping the time period (T) constant.

T = TON + TOFF

Where TON is the conduction period of a thyristor

TOFF is the blocking period of a thyristor

For a step-down chopper is operating on time ratio control principle,

\({V_0} = \alpha {V_s} = \frac{{{T_{on}}}}{T}{V_s}\)

Calculation:

Given that, frequency (f) = 2 kHz

Time period (T) = 1/f = 0.5 ms

Output voltage (V₀) = 170 V

Input voltage (V_in) = 230 V

\(\frac{{{V_0}}}{{{V_{in}}}} = \frac{{{T_{ON}}}}{T}\)

\(\Rightarrow {T_{ON}} = \frac{{170}}{{230}} \times 0.5 \times {10^{ - 3}} = 0.369\;ms\)