GATE 2016 EE – Question 55

Power Electronics · Static V-I characteristics and firing/gating circuits for Thyristor, MOSFET, IGBT · 2 marks · Numerical answer

The voltage ($v_s$) across and the current ($i_s$) through a semiconductor switch during a turn-ON transition are shown in figure. The energy dissipated during the turn-ON transition, in mJ, is ________.

The switch voltage $v_s$ stays at 600 V for the first $T_1 = 1\ \mu$s, then falls linearly to 0 over the next $T_2 = 1\ \mu$s. The switch current $i_s$ rises linearly from 0 to a peak of 150 A over $T_1$, then drops to a steady 100 A (a 50 A drop) and stays at 100 A during $T_2$ and afterwards.

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: 74 to 76

Explanation

In the first interval the voltage is 600 V while the current ramps from 0 to 150 A, so the average power is $600 \times 75 = 45$ kW and the energy is $45\ \text{kW} \times 1\ \mu\text{s} = 45$ mJ. In the second interval the current is 100 A while the voltage falls from 600 V to 0, so the average power is $100 \times 300 = 30$ kW and the energy is 30 mJ. The total is $45 + 30 = 75$ mJ.