8/3/2019 Power Semi Conducter EEE

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PSD IMPORTANT QUESTIONS:

UNIT:1

1.  Draw the output waveforms and explain the analysis of 1-phase fully controlled converter fed to

dc series motor? 

2.  A 200v, 875rpm, 150Amps separately excited dc motor has an armature resistance of 0.06

ohms . it is fed f rom a single phase fully controlled  rectif ier with an Ac source of 220v ,50hz.

Calculate

(A)  Firing angle at rated motor torque and 750 rpm? 

(B)  Firing angle at rated motor torque and -750 rpm? 

(C)  Motor speed for =1600 and rated torque? 

3.  Draw the output waveforms and explain the analysis of 1-phase semi- controlled converter fed 

to dc separately excited motor? 

4.  The speed 20Hp .1000rpm, 210v series motor is controlled by 1-phase fully converter, the

combined f ield and armature circuit resistance is 0.25 ohms, Kaf 

=0.03 n-m/amp2 and K

res= 0.075

ohm/radian. The supply voltage is 230v. Assume continuous and ripple f ree motor current, 

determine the following for a f iring angle of =300 and speed 1500rpm 

(a)  Motor current

(b)  Motor torque? 

(c)  Supplu power f actor? 

UNIT-2:

1.  Draw the output waveforms at =600

for 3-phase fully controlled converter fed to series motor? 

2.  Draw the output waveforms at =300

for 3-phase half controlled converter fed to series motor? 

3.  Draw the output waveforms at =450 for 3-phase fully controlled converter fed to dc separatelyexcited motor? 

4.  Draw the output waveforms at =600

for 3-phase half controlled converter fed to dc separately

excited motor? 

Unit-3:

1.  Explain the following detail? 

(a)  Plugging 

(b)  Rheostatic braking? 

(c)  Regenetive braking? 

2.  Explain about the dual converter fed to dc motor both in circulating and non-circulating modes? 

3.  A 220v ,1600rpm ,60A separately excited motor with armature resistance of 0.6 ohms fed f rom 

a circulating current dual converter with ac source linre voltage of 165v Determine the

converter f iring angles for the following operating points.

(a)  Motoing operation at rated motor torque and 900rpm? 

(b)  Braking operation at rated motor torque and 900rpm? 

(c)  Braking operation at rated motor torque and -900rpm? 

8/3/2019 Power Semi Conducter EEE

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Unit-4:

1.  Explain the analysis of f irst-quadrant chopper? 

2.  Explain and obtain the equation for the speed of separately excited motor which is controlled by

a chopper? 

3.  A 230v, 500rpm, 4.1A armature resistance and inductance of 7056 ohms and 55mH resp, Rating of 1HP motor is driven with armature supplied f rom class A chopper and 240v. The

chopping f requency is constant at 50Hz. The minimum load torque is 5 n-m.

(a)Determine the value of ton for minimum load torque at 500rpm.

(b) Determine whether Ia is continuous for the conduction of (a).

© Determine the minimum value of Ton for which the current Is continuous at 500rpm and the

corresponding coupling torque? 

4.  A 230v, 1000rpm, 30A separately excited motor has armature resistance and inductance of 0.7

ohms and 50mH , motor is controlled in regenerating braking by a chopper operating at 800Hz

f rom a dc source of 230v . Assume continuous conduction.

(a)  Calculate duty ratio of chopper by rated torque and speed of 800 rpm (b)  What will be the motor speed for duty ratio of 0.62 rated motor torque.

(c)  What will be the maximum allowable speed of motor? If a chopper has a maximum duty

ratio of 0.9 and maximum allowable motor current is twice rated current.

(d)  Calculate the power fed to source for operating condition in (c)