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How eddy currents are generated?

Recent questions and answers in Electrical Machine

2 answers 22 views

Interpoles are meant for

answered Jun 24 in Electrical Machine
1 answer 47 views

What will happen if you increase the current in the motor?

answered Jun 1 in Electrical Machine
2 answers 109 views

what is the difference between synchronous and asynchronous motor?

answered Dec 29, 2018 in Electrical Machine
1 answer 109 views

What is the difference between an AC and DC generator?

answered Sep 25, 2018 in Electrical Machine
1 answer 53 views

What is the difference between synchronous and asynchronous motors?

answered Sep 25, 2018 in Electrical Machine
1 answer 97 views

Split phase induction motor

answered Sep 20, 2018 in Electrical Machine
1 answer 51 views

Describe the reason of using dc series motor for electric trains.

answered Sep 18, 2018 in Electrical Machine
2 answers 74 views

UNIT 1 fundamentals of AC rotating machine Contents 1.1 Introduction 1.2 Advantages 1.3 Parts of AC machines 1.4 Synchronous speed 1.5 AC winding 1.6 Winding factor (Coil pitch and distributed winding) 1.7 Distribution factor 1.8 EMF equation of alternator or generator 1.9 Numericals 1.10 Harmonic 1.11 Slot harmonics 1.12 Harmonics minimization

answered Aug 25, 2018 in Electrical Machine
2 answers 9 views

Skew of rotor bar eliminates   1. The effect of space harmonics   2. The entire effect of crawling   3. Magnetic noise   4. Vibration due to unequal force developed on rotor 

answered Aug 11, 2018 in Electrical Machine
2 answers 35 views

The fall in speed of a dc generator due to increase in load can be corrected by  (1) cooling the armature.. (2) increasing the excitation. (3) reducing the load voltage. (4) increasing the input to the prime mover

answered Aug 2, 2018 in Electrical Machine
1 answer 35 views

Equalizer rings are used in a dc machine to (A) provide mechanical balance (B) balance the flux produced by the poles (C) provide path for the circulating currents (D) overcome armature reaction 

answered Jul 28, 2018 in Electrical Machine
1 answer 39 views

How is a three phase cage induction motor self starting?

answered Jul 23, 2018 in Electrical Machine
1 answer 30 views

How does a single phase induction motor work?

answered Jul 8, 2018 in Electrical Machine
0 answers 100 views

Analyze the differences of FOC and DTC. The switching frequency of FOC is 1.3 kHz and the average switching frequency of DTC is the same.

asked Jun 23, 2018 in Electrical Machine
0 answers 142 views

I got some grapic drawing questions guys and I need to see the answers immediately. Stator voltage curve for each four different start up methods.

asked Jun 23, 2018 in Electrical Machine
1 answer 255 views

Can you guys explain the advantages of frequency converter against the star delta or soft starter?

answered Jun 22, 2018 in Electrical Machine
1 answer 25 views

Which motor is generally used in Tap Recorders? A) universal motor B) reluctance motor C) split phase motor D) hysteresis motor

answered Jun 17, 2018 in Electrical Machine
1 answer 21 views

Which one is not a valid condition for the wave winding? A) Back pitch and front pitch are of the same sign B) Back pitch and front pitch are odd numbers C) Back pitch and front pitch may differ by two and may be equal also D) Commutator pitch is always unity

answered Jun 17, 2018 in Electrical Machine
0 answers 98 views

In star-star connection of 3-phase transformer, the triplen harmonics are suppressed by using (A) star connected tertiary windings (B) delta connected tertiary windings (C) neutral conductor (D) additional insulation for the phases 

asked Jun 4, 2018 in Electrical Machine
0 answers 23 views

If two 3-phase transformers with unequal voltage ratios are connected in parallel, the result is (A) circulating current on no-load (B) no circulating current on no-load (C) dead short-circuit (D) equal no-load secondary emfs 

asked Jun 4, 2018 in Electrical Machine
0 answers 16 views

In a 6-pole wave wound dc machine the number of conductors is 70. The back pitch and commutator segments, respectively, are (A) 11and 35 (B) 12 and 34 (C) 13 and 35 (D) 14 and 34 

asked Jun 4, 2018 in Electrical Machine
0 answers 15 views

The number of brushes in a 6-pole double-layer lap wound dc machine is (A) 8 (B) 6 (C) 4 (D) 2 

asked Jun 4, 2018 in Electrical Machine
0 answers 17 views

The demagnetizing AT/pole of a 4-pole dc generator is 480. The number of conductors is 480 and the current in each conductor is 40 A. Then the required brush shift in mechanical degrees (A) 9° (B) 7° (C) 5° (D) 3° 

asked Jun 4, 2018 in Electrical Machine
0 answers 28 views

In a dc shunt generator critical field circuit resistance line is the line drawn (A) above the OCC (B) below the OCC (C) tangent to the saturation curve (D) tangent to the linear portion of OCC 

asked Jun 4, 2018 in Electrical Machine
0 answers 26 views

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
0 answers 28 views

As the speed increases, the torque developed by a dc servo motor (A) decrease with a negative slope (B) increases with a positive slope (C) remain constant (D) becomes unstable 

asked Jun 4, 2018 in Electrical Machine
0 answers 17 views

The starting torque of a V/f controlled inverter-fed 3-phase induction motor operating at 25 Hz as compared with the same motor operating at 50 Hz is (A) more (B) double (C) equal (D) less 

asked Jun 4, 2018 in Electrical Machine
0 answers 11 views

Regenerative breaking of ac-dc converter fed dc motor is possible when firing delay angle of SCRs is (A) 30° (B) 60° (C ) 90° (D) 120°

asked Jun 4, 2018 in Electrical Machine
0 answers 22 views

In slip-energy recovery scheme of converter-fed 3-phase induction motor, super synchronous speeds are possible by (A) injecting voltage into the stator (B) injecting voltage into the rotor (C) extracting voltage from the stator (D) extracting voltage from the rotor. 

asked Jun 4, 2018 in Electrical Machine
0 answers 10 views

The voltage collected by the pantograph of electric locomotive is (A) DC voltage (B) single-phase AC, 50 Hz (C) 3-phase AC, 50 Hz (D) single-phase AC, 25 Hz 

asked Jun 4, 2018 in Electrical Machine
0 answers 10 views

Fast acceleration and high-speed cruising electric traction drive motor is (A) separately excited dc motor (B) DC series motor (C) AC series motor (D) 3-phase squirrel cage induction motor 

asked Jun 4, 2018 in Electrical Machine
1 answer 14 views

 As compared to a split phase motor, a capacitor start motor has _____.

answered May 29, 2018 in Electrical Machine
0 answers 17 views

A commutator with a diameter of 50 cm rotates at 1000 r.p.m. If brush width is 1.5 cm, the time of commutation will be (a) 0.168 m sec (b) 0.374 m sec (c) 0.481 m sec (d) 0.573 m sec

asked May 25, 2018 in Electrical Machine
0 answers 12 views

Shunt generators are most suited for stable parallel operation as their voltage characteristics are (a) drooping (b) identical (c) linear (d) rising

asked May 25, 2018 in Electrical Machine
1 answer 4 views

For very low speed and high power applications the best suited ac motor is:

answered May 22, 2018 in Electrical Machine
1 answer 11 views

If the current in the armature of do series motor is reduced to 5%, the torque of the motor will become: (1) 50% of the previous value (2) 25% of the previous value (3) 150% of the previous value (4) 125% of the previous value

answered May 22, 2018 in Electrical Machine
1 answer 10 views

The steady-state fault current during a 3 phase terminal fault on a generator is limited by: (1) Transient reactance of the generator (2) Sub-transient reactance of the generator (3) Synchronous reactance of the generator (4) DC off—set during the instant of the fault

answered May 22, 2018 in Electrical Machine
1 answer 10 views

Skewing of rotor bars eliminate the: (1) Effect of space harmonics (2) Entire effect of crawling (3) Magnetic noise (4) Vibration due to unequal force developed on rotor

answered May 22, 2018 in Electrical Machine
1 answer 10 views

A pole pitch in electrical machine is: (1) Equal to 180° electrical (2) Equal to 180° mechanical (3) Less than 180° electrical (4) Greater Than 180° electrical

answered May 22, 2018 in Electrical Machine
1 answer 19 views

The phase sequence of a three-phase alternator will reverse if  A) The field current is reversed keeping the direction of rotation same. B) The field current remains the same but the direction of rotation is reversed C) The field current is reversed and also the direction of rotation is reversed D) None of the above

answered May 20, 2018 in Electrical Machine
1 answer 32 views

A 4-pole, 3-phase, double-layer winding is housed in a 36-slot stator for an ac machine with 60o phase spread. Coil span is 7 short pitches. Number of slots in which top and bottom layers belong to different phases is  (A) 24 (B) 18 (C) 12 (D) 0

answered May 18, 2018 in Electrical Machine
1 answer 27 views

For a 1.8o, 2-phase bipolar stepper motor, the stepping rate is 100 steps/second. The rotational speed of the motor in rpm is  (A) 15 (B) 30 (C) 60 (D) 90

answered May 17, 2018 in Electrical Machine
1 answer 22 views

The armature resistance of a permanent magnet dc motor is 0.8 Ohm. At no load, the motor draws 1.5 A from a supply voltage of 25 V and runs at 1500 rpm. The efficiency of the motor while it is operating on load at 1500 rpm drawing a current of 3.5 A from the same source will be  (A) 48.0% (B) 57.1% (C) 59.2% (D) 88.8%

answered May 17, 2018 in Electrical Machine
1 answer 12 views

A rotating electrical machine its self-inductances of both the stator and the rotor windings, independent of the rotor position will be definitely not develop  (A) starting torque (B) synchronizing torque (C) hysteresis torque (D) reluctance torque

answered May 17, 2018 in Electrical Machine
1 answer 39 views

For a linear electromagnetic circuit, the following statement is true  (A) Field energy is equal to the co-energy (B) Field energy is greater than the co-energy (C) Field energy is lesser than the co-energy (D) Co-energy is zero

answered May 17, 2018 in Electrical Machine
1 answer 25 views

The following motor definitely has a permanent magnet rotor  (A) DC commutator motor (B) Brushless dc motor (C) Stepper motor (D) Reluctance motor

answered May 17, 2018 in Electrical Machine
1 answer 33 views

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 (A) 23.06 kW (B) 24.11 kW (C) 25.01 kW (D) 26.21 kW

answered May 17, 2018 in Electrical Machine
1 answer 173 views

In a stepper motor, the detent torque means  (A) minimum of the static torque with the phase winding excited (B) maximum of the static torque with the phase winding excited (C) minimum of the static torque with the phase winding unexcited (D) maximum of the static torque with the phase winding unexcited

answered May 17, 2018 in Electrical Machine
1 answer 5 views

Distributed winding and short chording employed in AC machines will result in  (A) increase in emf and reduction in harmonics (B) reduction in emf and increase in harmonics (C) increase in both emf and harmonics (D) reduction in both emf and harmonics

answered May 17, 2018 in Electrical Machine
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