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

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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 by Shimroz123
1 answer 16 views

The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is  (1) 1000V (2) 100V (3) 600V (4) 10,000V

asked Apr 29, 2018 in Electrical Machine by Shimroz123
1 answer 31 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

asked May 18, 2018 in Electrical Machine by Shimroz123
1 answer 65 views

Number of commutator bars for a 4-pole, 2-layer, DC lap winding with 24 slots and one conductor per layer is (A) 48 (B) 24 (C) 192 (D) 96

asked Apr 28, 2018 in Electrical Engineering by Shimroz123
0 answers 25 views

In case of four pole, lap wound machine if the air gap under each pole is the same, then what will be the result?  (A) There will be reduced eddy currents (B) There will be reduced hysteresis loss (C) Current in each path will not be the same (D) It will result in higher terminal voltage

asked Apr 5, 2018 in Electrical Engineering by Shimroz123
1 answer 32 views

A 36 slot, 4 -pole, dc machine has a simplex lap winding with two conductors per slot. The back pitch and front pitch adopted could be respectively

asked May 3, 2018 in Electrical Machine by Shimroz123
1 answer 12 views

 An 8 pole lap wound DC shunt generator is supplying 295A to a load. The field current of the generator is 5A. The current per parallel path is: -  a) 300A b) 200A c) 150A d) 37.5A

asked Apr 11, 2018 in Electrical Engineering by Shimroz123
0 answers 18 views

The torque produced in a 4-pole machine is 100 Nm. If machine is re-wound with 6 ploes, other things remaining the unchanged, then the torque produced would be (1) 66.67 Nm (2) 100 Nm (3) 150 Nm (4) 133.33 Nm 

asked Apr 11, 2018 in Electrical Engineering by Shimroz123
1 answer 24 views

A 6 pole 3-phase wound-rotor induction machine is driven by another machine at 1800 rpm. The rotor of the induction machine is connected to a 50Hz system. If the mechanical rotation of the rotor is in the same direction as the rotor winding flux rotation, then frequency of the stator voltage will be

asked Apr 1, 2018 in Electrical Engineering by Shimroz123
0 answers 16 views

A 4 pole lap wound dc shunt motor rotates at the speed of 1500 rpm, having a flux of 0.4 mWb and total number of conductors 1000. The value of e.m.f. will be:  (A) 100 Volts (B) 0.1 Volts (C) 1 Volts (D) 10 Volts

asked Apr 9, 2018 in Electrical Engineering by Shimroz123
1 answer 13 views

A 8-pole, DC generator has a simplex wave-wound armature containing 32 coils of 6 turns each. Its flux per pole is 0.06 Wb. The machine is running at 250 rpm. The induced armature voltage is  (A) 96 V (B) 192 V (C) 384 V (D) 768 V

asked May 17, 2018 in DC generator by Shimroz123
0 answers 15 views

The number of parallel paths in armature winding of four pole wave winding connected dc machine having 22 coil sides is (1) 4 (2) 22 (3) 2 (4) 11 

asked Apr 11, 2018 in Electrical Engineering by Shimroz123
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 by Shimroz123
0 answers 7 views

The induced emf in the armature of a wave wound 4-pole d.c. machine having 100 armature conductors rotating at 600 r.p.m. and with a flux of 1 Wb per pole is (a) 1000 V (b) 2000 V (c) 200 V (d) 100 V

asked May 25, 2018 in DC machine by Shimroz123
0 answers 41 views

A 0.5 Hp, 6 pole wound rotor induction motor is excited by a 3 phase 60 Hz source. Calculate the frequency of the rotor current at standstill.  (A) 50 Hz (B) 30 Hz (C) 60 Hz (D) 120 Hz 

asked Apr 5, 2018 in Electrical Engineering by Shimroz123
1 answer 31 views

Brushes of DC machine are made up of ?

asked Mar 3, 2018 in Electrical Machine by Quiz
1 answer 28 views

The number of electrical degrees ‘passed through’ in one revolution of a 6-pole synchronous alternator is: A) 360 degree B) 720 degree C) 1080 degree D) 2160 degree

asked Jun 17, 2018 in Synchronous machine by Shimroz123
1 answer 15 views

 The number of parallel paths in the armature winding of a 4 -pole, wave connected d.c. machine having 28 coilside is : -  a) 28 b) 14 c) 4 d) 2

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

The function(s) of pole shoes in DC machine is/ are to : -  a) Support the field coils b) Reduce the reluctance of the magnetic path c) Spread out the flux to achieve uniform flux distribution in the air gap d) All of the above.

asked Apr 11, 2018 in Electrical Engineering by Shimroz123
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

asked May 22, 2018 in Electrical Machine by Shimroz123
1 answer 30 views

Aluminium is not used as winding wire for the armature of a dc machine because  (1) aluminium has low resistivity (2) a large winding space is taken by aluminium conductors and creates jointing problems (3) the thermal conductivity of aluminium is low (4) aluminium has low conductivity as compared to copper

asked Apr 29, 2018 in Electrical Machine by Shimroz123
1 answer 28 views

The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole)  (A) has q -axis current only (B) has d -axis current only (C) has both d and q axis currents (D) cannot be divided between q and d axis currents

asked Apr 29, 2018 in Electrical Machine 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 15 views

Total electrical degrees for a 4 pole AC machine is equal to

asked May 15, 2018 in Electrical Machine by Shimroz123
1 answer 15 views

A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is

asked May 8, 2018 in Electrical Machine by Shimroz123
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 

asked Jun 4, 2018 in Electrical Machine by Shimroz123
1 answer 17 views

In a dc machine, interpoles are used to  (1) neutralize the effect of armature reaction in the interpolar region (2) generate more induced emf in the armature (3) avoid interference of the armature flux with the main -field flux (4) reduce the demagnetizing effect of armature reaction

asked Apr 29, 2018 in Electrical Machine by Shimroz123
1 answer 16 views

In a DC shunt generator working on load, the brushes are moved forward in the direction of rotation, as a result of this, commutation will   (a) Improve but terminal voltage will fall   (b) Worsen and terminal voltage will fall   (c) Improve and terminal voltage will rise   (d) worsen and terminal voltage will rise 

asked May 13, 2018 in DC generator by Shimroz123
1 answer 9 views

In a DC motor, it is important to place the brushes along ______ A) Magnetic Neutral Axis B) Normal Geometric Axis C) Nominal Geometric Axis D) None of these

asked Apr 29, 2018 in Electrical Engineering by Shimroz123
1 answer 18 views

The number of poles of 8/6 stepper motor can be :

asked Apr 30, 2018 in Electrical Machine by Shimroz123
1 answer 21 views

In a graph, the number of independent loops is 6 and the number of independent cut sets is 5, The total number of branches in the graph is A) 9 B) 12 C) 10 D) 11

asked May 24, 2018 in Network Analysis by Shimroz123
1 answer 34 views

An 8 pole wound rotor induction motor operating on 60 Hz supply is driven at 1800 r.p.m. by a prime mover in the opposite direction of revolving magnetic field. The frequency of the rotor current is (a) 30 Hz (b) 60 Hz (c) 120 Hz (d) 180 Hz 

asked May 25, 2018 in Induction Machine by Shimroz123
1 answer 21 views

A centre zero ammeters connected in the rotor circuit of a 6-pole 50 Hz induction motor makes 30 oscillations in one minute. The rotor speed is

asked Apr 1, 2018 in Electrical Engineering by Shimroz123
1 answer 22 views

In a double squirrel cage induction motor, good starting torque is produced as (A) Large current flows through the outer high resistance winding. (B) Large current flows through the inner high resistance winding. (C) Small current flows through the outer high resistance winding. (D) Large current flows through the inner low resistance winding.

asked May 8, 2018 in Electrical Machine by Shimroz123
1 answer 14 views

In a DC machine, which of the following statements is true ?  (A) Compensating winding is used for neutralizing armature reaction while interpole winding is used for producing residual flux (B) Compensating winding is used for neutralizing armature reaction while interpole winding is used for improving ... winding is used for neutralizing armature reaction (D) Compensation winding is used for improving commutation while interpole winding is used for producing residual flux

asked May 17, 2018 in DC machine by Shimroz123
0 answers 21 views

If the back emf of a dc motor is doubled and its speed is also doubled, the torque developed in the machine will  (1) get doubled (2) become 4 times (3) get halved (4) remain unaltered

asked Apr 10, 2018 in Electrical Engineering by Shimroz123
0 answers 39 views

The rotor winding of a three phase wound rotor induction motor is equipped with a three phase diode rectifier connected to the slip rings and rectifier output is connected with chopper drive. Compared to conventional rotor resistance control scheme, the chopper controlled method  A) Enhances the motor rating B) Maintains the motor rating as such C) Derates the motor D) None of the above 

asked Apr 9, 2018 in Electrical Machine by Zeeshan
1 answer 11 views

The rotor frequency for a 3-phase 6-pole, 1000 r.p.m. induction motor with a slip of 0.04 is (a) 2 Hz (b) 4 Hz (c) 6 Hz (d) 8 Hz  

asked May 25, 2018 in Induction Machine by Shimroz123
1 answer 54 views

A 6-pole, 50Hz, 3-φ induction motor is running at 950 r.p.m. and has Cu loss of 5kW. The rotor input is (a) 10 kW (b) 95 kW (c) 100 kW (d) 9.5 kW 

asked May 25, 2018 in Induction Machine by Shimroz123
0 answers 19 views

The power input to the rotor of a 400V, 50 Hz 6 pole three phase induction motor is 20kW. The slip is 3%. The frequency of rotor currents is: (A) 1 Hz (B) 1.5 Hz (C) 2 Hz (D) 1 2 Hz

asked Apr 14, 2018 in Electrical Engineering by Shimroz123
1 answer 16 views

A 100 turn coil has an inductance of 6 mH. If the number of turns is increased to 200, all other quantities remaining the same, the inductance will be:

asked May 22, 2018 in Inductance by Shimroz123
1 answer 38 views

What are the slot wedges in a DC machine made of?   (a) Mild steel (b) Silicon steel (c) Fibre (d) Cast iron

asked May 13, 2018 in DC machine by Shimroz123
1 answer 28 views

A separately excited d.c. machine is coupled to a 50 Hz, three-phase, 4-pole induction machine as shown in the figure. The Dc machine is energized first and the machines rotate at 1 600 1pm. Subsequently the induction machine is also connected to a 50 Hz, three phase source, the phase sequence being consistent with the direction of rotation. In steady state

asked May 20, 2018 in DC machine by Shimroz123
1 answer 25 views

A DC reactor is connected in series with each pole of a converter station in order to: A) prevent commutation failures in the inverter B) supply reactive power to the converter C) improve system stability D) increase the power transfer capability

asked Jun 4, 2018 in Power system by Shimroz123

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