🔍
A synchronous motor operates at 0.8 pf lagging. If the field current of the motor is continuously increased 

1. The power factor decreases upto a certain value of field current and thereafter it increases. 

2. The armature current increases upto a certain value of field current and thereafter it decreases. 

3. The power factor increases upto a certain value of field current and thereafter it decrease 

4. The armature current decreases upto a certain value of field current and thereafter it, increases.

 From these, the correct answer is (a) 1, 2 (b) 3, 4 (c) 1, 3 (d) 2, 4
0 like 0 dislike

1 Answer

A synchronous motor operates at 0.8 pf lagging. If the field current of the motor is continuously increased 

1. The power factor decreases upto a certain value of field current and thereafter it increases. 

2. The armature current increases upto a certain value of field current and thereafter it decreases. 

3. The power factor increases upto a certain value of field current and thereafter it decrease 

4. The armature current decreases upto a certain value of field current and thereafter it, increases.

 From these, the correct answer is (a) 1, 2 (b) 3, 4 (c) 1, 3 (d) 2, 4

0 like 0 dislike

Related questions

A 12 -pole, 440 V, 50 Hz, 3 -phase synchronous motor takes a line current of 100 A at 0.8 pf leading. Neglecting losses, the torque developed will be
Answer : A 12 -pole, 440 V, 50 Hz, 3 -phase synchronous motor takes a line current of 100 A at 0.8 pf leading. Neglecting losses, the torque developed will be 1165 Nm ...

View solution
0 like 0 dislike
1 answer

An induction motor operating at 0.8 pf lagging is consuming 300 kW. A zero real power consuming synchronous motor is connected across the induction motor to raise the pf to 0.92 lagging. The reactive power drawn by the synchronous ... a. - 352 kVAR b. - 225 kVAR c. - 127.8 kVAR d. - 97.2 kVAR

View solution
0 like 0 dislike
0 answers

A three-phase synchronous motor has a terminal voltage of 460 V and a terminal current of 120 A at a power factor of 0.95 lagging, synchronous reactance of 1.68 ohm and the field current is 47 A. The field to armature mutual ... _____________.      (a). 20mH   (b). 16mH   (c). 24mH   (d). 22mH
Answer : 22...

View solution
0 like 0 dislike
1 answer

A synchronous motor is operating on no-load at unity power factor. If the field current is increased, power factor will become (A) Leading & current will decrease (B) Lagging & current will increase. (C) Lagging & current will decrease. (D) Leading & current will increase.
Answer : Ans: A Initially synchronous motor is operating at no load and unity power factor. When field current increases, the excitation will increase. Therefore, p.f will be leading and current will be I CosΦ < I...

View solution
0 like 0 dislike
1 answer

A 400 V, 50 Hz 30 hp, three-phase induction motor is drawing 50 A current at 0.8 power factor lagging. The stator and rotor copper losses are 1.5 kW and 900 W respectively. The friction and windage losses are 1050 W and the ... the motor will be (A) 23.06 kW (B) 24.11 kW (C) 25.01 kW (D) 26.21 kW
Answer : A 400 V, 50 Hz 30 hp, three-phase induction motor is drawing 50 A current at 0.8 power factor lagging. The stator and rotor copper losses are 1.5 kW and 900 W respectively. The friction and windage losses are 1050 W and the core losses are 1200 W. The air-gap power of the motor will be 25.01 kW ...

View solution
0 like 0 dislike
1 answer

50.5k questions

47.1k answers

240 comments

7.0k users