Module 3

A fully controlled converter uses

• Diodes only

• Thyristors only

• both diodes and thyristors

• none of the mentioned

A single phase full-converter using R load is a _________ quadrant converter and that using an RL load without FD is a __________ quadrant converter

• one, one

• two, one

• one, two

• two, two

The average output voltage is maximum when SCR is triggered at ωt =

• π

• 0

• π/2

• π/4

In the method of phase control, the phase relationship between ___ & ___ is controlled by varying the firing angle

• supply current, supply voltage

• end of the load current, end of the load voltage

• start of the load current, start of the load voltage

• load current, load voltage

In a single phase half-wave thyristor circuit with R load & Vs=Vm sinωt, the maximum value of the load current can be given by

• 2Vm/R

• Vs/R

• Vm/2

• Vs/2

In a semi-converter with RLE load during the freewheeling period, the energy is

• fed back to the source

• fed to the inductor(L) and absorbed by E

• absorbed by the L & E and dissipated at R

• fed to the L & E and dissipated at R

The expression for the average output voltage with Vs = Vm sinωt and firing angle α

• (Vm/π) cosα

• (Vm/π) (1+cosα)

• (2Vm/π) cosα

• (2Vm/π) (1+cosα)

A single-phase symmetrical semi-converter employs

• one SCR and one diode in each leg

• two SCRs and two diodes in each leg

• two SCRs in each leg

• two diodes in each leg

Dual converters provide

• two quadrant operation

• three quadrant operation

• four quadrant operation

• none of the mentioned

A dual converters has

• two full converters in series

• two half converters in series

• two full converters in anti-parallel

• two half converters in anti-parallel