EE8552_PE_QUIZ_UNIT 2_PART2

In a 3 phase bridge rectifier the ripple frequency is

• Equal to the input frequency

• Twice the input frequency

• Three times the input frequency

• Six times the input frequency

If the firing angle becomes negative, then the rectifier begins to work as

• A rectifier

• An inverter

• A chopper

• A regulator

In a 3 phase half wave rectifier, when firing angle is less than 90 degree, then the average dc output voltage becomes

• Positive

• Negative

• Zero

• None of these

In dual converters,

• Both rectifiers provides positive current to the load

• Both rectifiers provide negative current to the load

• One rectifiers provide positive current to the load and the other negative current

• One rectifier provide positive current to the source and the other negative current to the load

The sum of all phase current in a star connected primary winding with no neutral connection is equal to

• Phase current

• Three times the phase current

• Three times the line current

• Zero at all times

For power output higher than 15 kW, the suitable rectifier is

• Single phase

• 3 phase

• Poly phase

• Only (b) and (c)

In a three-phase halfwave rectifier, the ratio of average output voltage to per phase maximum AC voltage is

• 1

• 1.169

• 0.827

• 1.571

Which of the following converter circuits would require a neutral point?

• 3-phase semi-converter

• 3-phase full converter

• 3-phase full converter with freewheeling diode

• 3-phase half wave converter

In a 3-φ semi converter for firing angle less than or equal to 60°, wheeling diode conducts for

• Zero degree

• 30°

• 45°

• 75°

In a 3-phase voltage source inverter used for speed control of induction motor, antiparallel diodes are used across each switching device. The main purpose of diodes is to:

• Protect the switching devices against overvoltage

• Provide the path for freewheeling current

• Allow the motor to return energy during regeneration

• Help in switching off the devices