Power Electronics Objective Questions – Set 2

60 thyrsistors are connected in series and parallel to form a 10 KV and 5.5 KA switch. Each thyristor is rated for 1.2 KV, 1 KA. The no. of parallel path are 6. The efficiency of the switch is

Rise time is defined by the interval when

Why resistor is used in Snubber circuit ?

Typical range of thyristor turn OFF time is

What may happen high dV / dt?

How can we protect SCR from thermal conditions ?

Which of the following is used in SCR to protect from high dV / dt?

Materials used in heat sink should have

Snubber circuit is used with SCR

A thyristor string is made of a no. of SCR connected in series and parallel. The string have volume and current of 11 KV and 4 KA. The voltage and current rating of available SCRs are 1800 V and 1000 A. For a string efficiency of 90 % let the number of SCRs in series and parallel are a and b respectively. Then the value of a and b will be

ON state voltage drop across SCR lie between the range

The typical time of rising time lies between

During gate recovery time

By which one of the following we can measure the reliability of a string?

Which of the following is used in heat sink?

Calculate the maximum voltage that can be safely blocked by the string shown in figure, if maximum allowable leakage current is 2 mA?

Figure shows two thyristors rated 400 A sharing a load current. Current through T₂ is 180A. Current through T₁ will be

Dynamic equalizing circuit is used for

Maximum power loss occurs during

4 thyristors rated 200 V in series. The operating voltage of the string is 0.600 V. Derating factor of the string is

The latching current of GTO should be of order

What happen due to high di / dt?

Delay time is defined by the interval when

To meet high current demand we use SCRs in

During which time maximum conduction spreading take place in the thyristor during turn ON?

Which statement is true ?

Spread time is defined as the interval during which

During reverse recovery time

What is used to protect a thyristor from high di / dt conditions?

SCRs are used in series to meet