Rajasthan Polytechnic Third Year Paper 2016 – Power & Industrial Electronics

Rajasthan Polytechnic Third Year Paper 2016 – Power & Industrial Electronics

The break down voltage of a thyristor is 200 V. Peak value of input sinusoidal is 400 V. When 1.5 mA gate pulse is provided, then thyristor is fired. The value of conduction angle will be
(a) 45 degree
(b) 120 degree
(c) 150 degree
(d) 30 degree

If the flow of current through SCR comes below to holding current then
(a) SCR is damaged
(b) Gate will retain the control on it
(c) Potential across it is decreased across it.
(d) The internal resistance is increased

In which application TRIAC is not used?
(a) In phase control
(b) In light dimming
(c) Static switch
(d) AC to DC conversion

Which is known as carrier gating from the following?
(a) Triggering of SCR by pulse
(b) Turn off SCR by providing negative pulse on gate
(c) dv/dt control of SCR
(d) Gate protection circuit of SCR

Thyristers are not fabricated by germanium because
(a) This is not a stable semi conductor
(b) The element of group V cannot be diffused in it
(c) The current bearing capacity is less
(d) The leakage current is more

The latching current of SCR is
(a) Less than 10%
(b) 10-20%
(c) 20-25%
(d) 25-30% of rated current

How many number of SCRs of 800 V rating are required to connect in series for 3 kV circuit, when decreasing factor is 15%?
(a) 3
(b) 4
(c) 5
(d) 6

Automatically turn off of SCR in negative half cycle of AC supply is called
(a) ‘A’ class commutation
(b) ‘B’ Class commutation
(c) ‘F’ Class commutation
(d) ‘D’ Class commutation

If a diode is a single phase full wave rectifier produces the short circuit, then
(a) Supply will short circuited
(b) Rectifier will be continuously in working as full wave rectifier
(c) Rectifier will be continously in working as half wave rectifier
(d) All diode will be short circuited

The device commonly used for triggering a triac is
(a) diode
(b) transistor
(c) zener diode
(d) diac

The fundamental ripple frequency of a single phase half wave rectifier for the input of 220 volt and 50 Hz.
(a) 50 Hz
(b) 100 Hz
(c) 150 Hz
(d) 300 Hz

An inverter converts
(a) ac into dc
(b) ac into ac of higher frequency
(c) ac into ac of lower frequency
(d) dc into ac

Free wheeling diodes are used across the R-L load because
(a) To block the break down current
(b) To rectify the current
(c) To block the flow of current in reverse direction
(d) All of the above