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A step-up chopper is used to feed a load at 400 V dc fr om a 250 V dc source. The inductor current is continuous. If the ‘off’ time of the switch is 20 s, the switching frequency of the chopper in kHz is _____.
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- 32.5
- 21.5
- 31.0 to 31.5
- 31.0
Correct Option: C
Vo = 400 V
Vs = 250 V
Toff = 20 μsec
F = ?
| Vo = | ||
| 1 - D |
| ∴ 1 - D = | ||
| 1 - D |
| 1 - D = | ||
| 400 |
Now Toff = (1 – D) T
| ∴ T = | = | × 400 | ||
| 1 - D | 250 |
| Now f = | = | |||
| T | 20 × 400 |
∴ f = 31.25 kHz
