Question

A type A chopper has input dc voltage of 200 V and a load of R = 10 $\Omega$ in series with L = 80 mH. If the load current varies linearly between 12 A and 16 A, the time ratio $T_{on}/T_{off}$ for this chopper is

Answer 1

Average load current = $\frac{12+16}{2}$ = 14 A.

Average load voltage $V_0=I_{0}R=14\times 10=140V$

$V_0=\alpha V_s$
Since the chopper is step down or type-A,

$140=\alpha 200$

$\alpha =\frac{140}{200}=0.7$

$\frac{T_{on}}{T_{on}+T_{off}}=0.7$

$0.3T_{on}=0.7T_{off}$

$\frac{T_{on}}{T_{off}}=2.33$