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In a synchronous motor, damper winding is provided to 

 (a) stabilize rotor motion (b) suppress rotor oscillations (c) develop necessary starting torque (d) (b) and (c) both 

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Damper winding is provided in 3 phase synchronous motors to :

asked Apr 29, 2018 in Electrical Machine by Shimroz123
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Damper winding in a synchronous motor

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What type of excitation is given to the rotor winding of a synchronous motor?  (A) DC supply at 100 -250 V (B) AC supply at 400 V (C) Revolving field (D) Induction from stator currents 

asked Apr 5, 2018 in Electrical Engineering by Shimroz123
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The damping winding in synchronous motor is generally used to?

asked Mar 18, 2018 in Synchronous machine by Shimroz123
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 When a synchronous motor is started, the field winding is initially :  a)excited by a d.c. sources b) short circuited c) open circuited d) none of these

asked Apr 11, 2018 in Electrical Engineering by Shimroz123
1 answer 14 views

Under which of the following conditions is a DC motor provided with compensating winding used?  1. Wide range of speed control above normal  2. Wide range of steady load variation with no speed control  3. Wide range of rapid variation in load.   Select the correct answer using the codes given below:   (a) 1, 2 and 3 (b) 2 and 3 (c) 1 and 2 (d) 1 and 3

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In large capacity transformers, 5% of the turns at the end of hv winding are provided with extra insulation so as to provide protection  (1) against corona (2) against lightning (3) due to surges occurring during switching operation (4) All of these

asked Apr 10, 2018 in Electrical Engineering by Shimroz123
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In synchronous motor, does the winding losses vary with load?

asked Mar 3, 2018 in Electrical Machine by Quiz
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The copper armature winding of a motor is subjected to an operating temperature of 80°C. The room temperature is 20° C. The percentage change in resistance of the armature winding from cold staring condition to normal running will be nearly:

asked Apr 1, 2018 in Electrical Engineering by Shimroz123
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The maximum torque that a synchronous motor can deliver is proportional to (1) 1/V2 (2) 1/V (3) V (4) V2

asked Apr 11, 2018 in Electrical Engineering by Shimroz123
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If a four pole synchronous generator driven at 1500 rpm feeds a 6-pole induction motor, which is loaded to run at a slip of 5%, then speed of the motor will be   (a) 1000 rpm (b) 950 rpm (c) 1500 rpm (d) 1450 rpm

asked Apr 10, 2018 in Electrical Engineering by Shimroz123
1 answer 21 views

A 3~phase synchronous motor, connected to infinite bus, is operating at no load at normal excitation. The field excitation of the motor is first decreased to zero and then increased in the reverse direction. The armature current of the synchronous motor will:  (1) Remain constant. (2) First decrease and then increase, (3) Increases continuously (4) First increase and then decreased

asked Apr 9, 2018 in Electrical Engineering by Shimroz123
1 answer 19 views

In a 4-pole wave winding connected dc motor, the cross-magnetizing AT/pole for a brush shift of θ radians (A) Armature amp-conductors × (θ/360o) (B) Armature amp-turns × (θ/360o) (C) Armature amp-conductors × (1/4 - θ/360o) (D) Armature amp-conductors × (1/8 - θ/360o)

asked Apr 28, 2018 in Electrical Engineering by Shimroz123
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A 200 V dc motor takes a field current of 2 A to generate a back emf of 180 V. If the field winding resistance is 80 Ω, the resistance of the shunt field regulator is (A) 10 Ω (B) 20 Ω (C) 100 Ω (D) 180 Ω

asked Jun 4, 2018 in Electrical Machine by Shimroz123
1 answer 30 views

The running winding of a single phase motor on testing with meggar is found to be ground. Most probable location of the ground will be?

asked Mar 20, 2018 in Induction Machine by Shimroz123
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Copper shading is provided in energy meter to  (A) Bring flux exactly in quadrature with applied voltage (B) To increase speed of aluminium disc (C) To count the rotation (D) To balance the system from vibration 

asked Apr 5, 2018 in Electrical Engineering by Shimroz123
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Variation in dc excitation of a synchronous motor causes variation in   (a) Speed of motor (b) Power factor (c) Armature current (d) Both armature current and power factor 

asked Apr 10, 2018 in Electrical Engineering by Shimroz123
1 answer 13 views

In a 3-phase synchronous motor;  (A) the speed of the stator MMF is always more than that of the rotor MMF (B) the speed of the stator MMF is always less than that of the rotor MMF (C) the speed of the stator MMF is synchronous speed while that of the rotor MMF is zero (D) the rotor and the stator MMF are stationary with respect to each other

asked Apr 9, 2018 in Electrical Engineering by Shimroz123
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Maximum power developed in a synchronous motor occurs at a coupling angle of:  (A) 120° (B) 60° (C) 90° (D) 0° 

asked Apr 5, 2018 in Electrical Engineering by Shimroz123
0 answers 51 views

If the stator winding of a three-phase induction motor is delta connected, the rotor winding   (a) should be delta connected (b) should be star connected (c) should not be delta connected (d) may be delta or star connected 

asked Apr 10, 2018 in Electrical Engineering by Shimroz123
0 answers 19 views

The stator of a 3 phase, 10 pole induction motor possesses 120 slots. If a lap winding is used, calculate the coil pitch, if the coil width extends from slot 1 to slot 11.  (A) 72.12% (B) 83.30% (C) 12% (D) 42% 

asked Apr 5, 2018 in Electrical Engineering by Shimroz123
1 answer 24 views

A cylindrical rotor synchronous motor is switched on to the supply with its field windings shorted on themselves, the motor will .  A) Not start B) Start but will not run at synchronous speed C) Start as an induction motor and then run as a synchronous motor D) Start and run as a synchronous motor

asked May 20, 2018 in Synchronous machine by Shimroz123
1 answer 14 views

A three phase, salient pole synchronous motor is connected to an infinite bus. It is operated at no load a normal excitation. The field excitation of the motor is first reduced to zero and then increased in reverse direction gradually. Then the armature current.  (A) Increases continuously (B) First increases and then decreases steeply (C) First decreases and then increases steeply (D) Remains constant

asked May 17, 2018 in Synchronous machine by Shimroz123
1 answer 31 views

A three-phase synchronous motor connected to ac mains is running at full load and unity power factor. lf its shaft load is reduced by half and field current is held constant then its new power factor will be

asked Apr 28, 2018 in Electrical Machine by Shimroz123
1 answer 17 views

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 ... field current and thereafter it, increases.  From these, the correct answer is (a) 1, 2 (b) 3, 4 (c) 1, 3 (d) 2, 4

asked May 13, 2018 in Electrical Engineering by Shimroz123
0 answers 23 views

A synchronous motor at no load condition is known as synchronous condenser and improves the (a) stability (b) efficiency (c) power factor (d) frequency of the integrated system

asked Apr 14, 2018 in Electrical Engineering by Shimroz123
0 answers 21 views

A synchronous motor is delivering 80% of its rated output and is operating at UPF. If its excitation is increased, then  (1) the output delivered gets increased (2) its pf becomes lagging (3) the output delivered gets decreased (4) its pf becomes leading

asked Apr 10, 2018 in Electrical Engineering by Shimroz123
0 answers 20 views

A synchronous motor is essentially a motor with   (a) Constant speed (b) Leading power factor (c) Unity power factor (d) Lagging power factor 

asked Apr 10, 2018 in Electrical Engineering by Shimroz123
0 answers 9 views

In a synchronous motor, if β is impedance angle and δ is torque angle, then the maximum developed mechanical power is obtained when (a) δ = 180 – 2β (b) δ = 2β (c) δ = 180 – β (d) δ = β  

asked May 25, 2018 in Synchronous machine by Shimroz123
2 answers 73 views

The maximum power in a synchronous motor (for a given excitation) is produced when the power angle is equal to: (A) 0° (B) 45° (C) 60° (D) 90°

asked Apr 11, 2018 in Computer Engineering by Shimroz123
1 answer 50 views

Laminations in the transformer core are provided to avoid (a) continuous air gap (c) to reduce exiting current (b) to reduce the weight (d) to reduce copper losses

asked Apr 14, 2018 in Electrical Engineering by Shimroz123

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