PROTECTION DEVICES

The snubber circuit is used in thyristor circuits for

• triggering

• phase shifting

• di/dt protection

• Over voltage

Snubber circuits are used to protect thyristor from which of the following?

• High di/dt and low dv/dt

• High dv/dt and low di/dt

• High dv/dt and high di/dt

• low di/dt and low dv/dt

For an SCR, dv/dt protection is achieved through

• RL in series with SCR

• RC across SCR

• L in series with SCR

• L across SCR

The snubber circuit used to shape the turn on switching trajectory of thyristor and/or to limit di/dt during turn on is

• L – R snubber polarized

• R – C snubber polarized

• R – C snubber unpolarized

• L – R snubber unpolarized

.For an SCR, di/dt protection is achieved through

• R in series with SCR

• RL in series with SCR

• L in series with SCR

• L across SCR

The local hot spot formation in the cross-section of the SCR is avoided by

• reducing the junction temperature

• applying gate current nearer to the maximum gate current

• using only R loads

• proper mounting of the SCR on heat sink

The local hot spot formation in the cross-section of the SCR is due to _____

• sudden change in voltage

• sudden change in current

• short circuit

• faulty current

The effect of over-voltages on SCR are minimized by using

• RL circuits

• Circuit breakers

• Varistors

• di/dt inductor

Snubber’s circuit is used to reduce __________

• Mechanical stresses

• electrical stresses

• Both a & b

• none of these

Issues related to temperature can be avoided by using

• Natural Cooling Methods

• Forced Cooling Methods

• Combination of Forced and natural Cooling