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What is the back EMF of a dc motor?
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Answer :

The armature may burn if the back e.m.f. of a D.C. motor vanishes suddenly.

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Description :

What is back EMF of synchronous motor?

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Description :

What is the back EMF of the motor?

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Description :

The back emf of synchronous motor depends on?

Answer :

The back emf of synchronous motor depends on load angle.

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Description :

Answer :

The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is 0.5.

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Description :

What is back emf? 

Answer :

Back EMF: When a current carrying conductor is placed in a magnetic field it experiences a force; when it moves due to the force it (conductor) cuts the magnetic field due to which an emf is ... (hence the applied armature voltage) is opposed by the induced emf which is therefore called as Back emf.

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Description :

What is back EMF in inductor?

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Description :

What is the back EMF in Transformers?

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Description :

What is the back EMF?

Answer :

When the armature of a d.c. motor rotates under the influence of the driving torque, the armature conductors move through the magnetic field and hence e.m.f. is induced in them as in a generator. The ... that energy conversion in a d.c. motor is only possible due to the production of back emf.

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Description :

Answer :

In case of D.C. shunt motors the speed is dependent on back e.m.f. only because flux is practically constant in D:C. shunt motors.

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Description :

Do AC induction motors have back EMF?

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Description :

The counter e.m.f. of a d.c. motor?

Answer :

The counter e.m.f. of a d.c. motor helps in energy conversion.

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Description :

Answer :

When the armature of a D.C. motor rotates, e.m.f. induced is back e.m.f.

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Description :

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

Answer :

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 1000V

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Description :

What would happen if a DC motor was supplied with AC ?

Answer :

With three phase induction motor, humming and not rotate, but if single phase universal motor like air blower, home mixture, motor run on constant speed..speed variation not possible...

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Description :

What are the advantages of DC series motor?

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Description :

What is the principle of DC motor?

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Description :

What is the RPM of a DC motor?

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Description :

What are the speed control methods of dc motor?

Answer :

Field control of DC motor Armature control of DC motor

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Description :

Answer :

If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will increase.

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Description :

Answer :

In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will remain unchanged.

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Description :

As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit?

Answer :

As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit a resistance is connected in series with armature.

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Description :

A separately excited dc motor operating in first quadrant is fed from 3-phase semi -converter free -wheeling diode is open circuited, then the motor :  (A) can be operated in first quadrant (B) can be operated in first & second quadrants (C) can be operated in first & fourth quadrants (D) cannot be operated

Answer :

A separately excited dc motor operating in first quadrant is fed from 3-phase semi -converter free -wheeling diode is open circuited, then the motor : can be operated in first & fourth quadrants

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Description :

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

Answer :

In a DC motor, it is important to place the brushes along Magnetic Neutral Axis

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Description :

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)

Answer :

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

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Description :

Why a dc series motor has a high starting torque?

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Description :

If field current is decreased in shunt dc motor, the speed of the motor (a) remains same. (b) increases. (c) decreases. (d) none of the above.

Answer :

increases

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Description :

State the function of following parts of DC motor : i) Yoke ii) Poles iii) Field winding iv) Commutator. 

Answer :

Function : i) Yoke: The yoke serves the following two purposes. i) It supports the other components such as poles and provides mechanical protection for whole machine. ii) It forms a part of ... one pole to another and thus to help the motor to develop a continuous and unidirectional torque  

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Description :

Which type of starter is used to start the DC motor?

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Description :

Why dc series motor should not be started at no load?

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Description :

Explain concept of back emf in DC machine. State how it governs armature current. 

Answer :

Back emf: When the armature of DC machine rotates under the influence of driving torque, the armature conductors move in the magnetic field and cut it and hence emf is induced in them. The ... flow of armature current i.e. it automatically changes the armature current to meet load requirements.

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Description :

Why does the speed of a DC shunt motor decrease as the load increases?

Answer :

Because if the load is increasing then the torque must also be increase. If not then the speed of motor will decrease.

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Description :

A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be

Answer :

A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be 474 V

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Description :

A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is

Answer :

A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is 36 Ohm

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194 views 1 answer
Description :

In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is :

Answer :

In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is : 0.075

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83 views 1 answer
Description :

The function of a brush and commutator arrangement in a dc motor is to  (1) produce unidirectional torque (2) produce unidirectional current in the armature (3) help in changing the direction of rotation of the armature (4) reduce sparking

Answer :

The function of a brush and commutator arrangement in a dc motor is to produce unidirectional torque

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1.7k views 1 answer
Description :

The no-load speed of a single-phase SCR bridge converter fed separately excited dc motor operating at a firing delay angle, α and flux, Φ (A) directly proportional to α and Φ (B) inversely proportional to α and Φ (C) directly proportional to α and inversely proportional to Φ (D) directly proportional to Φ and inversely proportional to α

Answer :

The no-load speed of a single-phase SCR bridge converter fed separately excited dc motor operating at a firing delay angle, α and flux, Φ directly proportional to α and inversely proportional to Φ

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Description :

State at least one function and the material used for the following parts of DC Motor.

Answer :

Part Function Material Yoke -Provides mechanical support for poles -Acts as protecting cover for machine -Provides path for magnetic flux Cast Iron OR Cast Steel Field Winding - ... Pole core  Provides mechanical support to field winding. Cast Iron OR Cast Steel

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Description :

State the modification to be done in dc series motor to work satisfactorily as ac series motor. State applications of ac series motor.

Answer :

Modifications are necessary in a dc series motor so that it operates satisfactorily on ac supply. The modifications are as follows:  1) AC series motor is built with a few field turns as ... and grinders 5) High speed vacuum cleaners 6) Sewing machines 7) Food processors 8) Drilling machine 

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Description :

DC motor gross torque example

Answer :

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117 views 2 answers
Description :

DC shunt motor

Answer :

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Description :

DC motor brake test numerical

Answer :

.embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

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Description :

Brake test on DC series motor

Answer :

.embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

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188 views 2 answers
Description :

State any four applications of DC shunt motor.

Answer :

Applications of DC shunt motor: 1) Lathe machines 2) drilling machines 3) milling machines 4) Printing machinery 5) Paper industry 6) centrifugal and reciprocating pumps 7) blowers 8)fans

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86 views 2 answers
Description :

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

Answer :

Electric trains require an inverse torque speed characteristics for proper operation. That is a higher torque is required at start (when speed is nil or low) and as the train picks up ... torque - speed characteristics of DC series motors match, these motors are suitable for electric trains

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120 views 1 answer
Description :

In DC motor iron losses are occurred in?

Answer :

In DC motor iron losses are occurred in the armature.

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Description :

Why DC motor is used for traction?

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Description :

Answer :

Induction motor is a AC motor it is also known as asynchronous motor .

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Description :

Chopper controlled DC motor

Answer :

Chopper controlled DC motor

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