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The D.C. motors preferred for traction applications beacuse the speed is inversely proportional to the torque and the torque is proportional to square of armature current.

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Description :

Which of the following test is usually conducted to determine the efficiency of traction motors ? (A) Field’s test (B) Swinburne’s test (C) Hopkinson’s test (D) Retardation test.

Answer :

Which of the following test is usually conducted to determine the efficiency of traction motors ? (A) Field’s test (B) Swinburne’s test (C) Hopkinson’s test (D) Retardation test.

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Answer :

D.C. shunt motors are used for driving machine tools.

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Why DC motor is used for traction?

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Description :

Which of the following motors is being extensively used in servo applications ? A. AC motor B. Field controlled dc motor C. Armature controlled dc motor D. None of these

Answer :

Which of the following motors is being extensively used in servo applications ? A. AC motor B. Field controlled dc motor C. Armature controlled dc motor D. None of these

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Answer :

During rheostat braking of D.C. series motors motor is run as a generator.

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Answer :

Differentially compound D.C. motors can find applications requiring low starting torque.

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Description :

Why are DC motors used in trains and not AC motors ?

Answer :

The reason is torque. torque is inversely proportional to speed..i.e when th knowe train comes to rest position to motion.. initial speed is zero..so it requires high starting torque for ... current will flow through field and armature coils then maximum torque is available at the intial condition.

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145 views 1 answer
Description :

Answer :

When two D.C. series motors are connected in parallel, the resultant speed is normal speed.

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Answer :

Starters are used with D.C. motors because to restrict armature current as there is no back e.m.f. while starting.

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Answer :

In case of conductively compensated D.C. series motors, the compensating winding is provided in series with armature winding.

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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 :

Answer :

In D.C. shunt motors as load is reduced the speed will remain almost constant.

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Description :

Which of the following motors can run on both AC and DC? A) Universal motor B) Dual wattage motor C) Flexible motor D) All the above

Answer :

Which of the following motors can run on both AC and DC? A) Universal motor B) Dual wattage motor C) Flexible motor D) All the above

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Description :

Suggest electric motors for i) traction ii) crane iii) lathe machine iv) domestic fan.

Answer :

i) Traction :- DC Series motor  ii) Crane :- DC Series motor  iii) Lathe machine :- 3 phase Induction motor or DC shunt motor  iv) Domestic fan :- 1 phase induction motor

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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 :

The motor used for electric traction is  (1) D.C. shunt motor (3) D.C. series motor  (2) D.C. compound motor (4) Synchronous motor

Answer :

The motor used for electric traction is D.C. series motor

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Description :

In electric traction for a trapezoidal speed-time curve, the time period is (A) free running speed period = constant speed period (B) free running period = coasting period (C) free running period + coasting period = constant speed period (D) average speed period = scheduled speed period

Answer :

In electric traction for a trapezoidal speed-time curve, the time period is free running period + coasting period = constant speed period

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Description :

In quadrilateral speed-time curve of electric traction system, the accelerations during successive time periods are ______ respectively.  (A) positive, negative and negative (B) positive, zero and negative (C) positive, positive and negative (D) positive, negative and zero

Answer :

In quadrilateral speed-time curve of electric traction system, the accelerations during successive time periods are positive, negative and negative respectively. 

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Description :

Answer :

An ideal traction system should have easy speed control, high starting tractive effort, equipment capable of with standing large temporary loads.

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Which motor is used in traction system?

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What is the traction system?

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MOSFET have high current losses due to High on state resistance. Hence MOSFET is used for low power applications.

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What are the factors to be considered while selection of motors for different drives?

Answer :

Following Factors are considered while selecting electric drive (Motor) for particular application:  Factors to be considered for selection of Electrical Drives:  1) Nature of Supply:- Whether supply ... , load equalization 7) Cost: - Capital, Running and maintenance cost should be less.  

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As hysteresis motors are free from mechanical and magnetic vibrations therefore these are considered as suitable for sound equipment.

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The standard full-load power factor ratings for synchronous motors are unity or 0.8 leading.

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The widely used series-parallel system of speed control of d.c. series motors in traction work gives a speed range of about (a) 1 : 2 (b) 1 : 3 (c) 1 : 4 (d) 1 : 6

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Description :

State which electric motors are generally used in electro agro systems with reason.

Answer :

1) 3 phase induction motor is used in electro agro system for water pumping from wells as 3 phase ac supply is easily available, cost of induction motor is less, maintenance free being rugged ... as 1 phase ac supply is easily available for domestic purpose, repair is simple and easily available.

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Description :

Stepper motors are used in  (1) printers (2) lifts (3) amplifiers (4) oscillators

Answer :

Stepper motors are used in printers 

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Description :

Slot harmonics are reduced in induction motors by using (A) fractional-pitch windings (B) fractional-slot windings (C) integral-slot windings (D) distributed windings

Answer :

Slot harmonics are reduced in induction motors by using fractional-slot windings

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Answer :

Synchronous motors are generally not self-starting because the direction of instantaneous torque reverses after half cycle.

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The efficiencies of transformers compared with that of electric motors of the same power are?

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Transformers have high efficiency than the same ratted motors

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What are the five types of single phase motors used in the industry?

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State factors for selection of motors as drive.

Answer :

Following Factors governing / or are considered while selecting electric drive (Motor) for particular application: Factors to be considered for selection of Electrical Drives: 1) Nature of Supply:- ... level, load equalization 7) Cost: - Capital, Running and maintenance cost should be less.

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A relay used for protection of motors against overload is :  (A) Impedance relay (B) Electromagnetic attraction type (C) Thermal relay (D) Buchholz's relay

Answer :

A relay used for protection of motors against overload is : Thermal relay

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A direct online starter is used for starting motors up to 5 H.P.

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The range of efficiency for shaded pole motors is 5% to 35%.

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For power factor correction, synchronous motors operate at no-load and greatly over-excited fields.

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Description :

Write two applications of D.C. series motor. 

Answer :

The applications of D.C. series motor: 1. Cranes 2. Hoists 3. Trolley and cars 4. Conveyors 5. For traction work i.e. electric locomotives 6. Elevator 7. Air compressor

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D.C. generator generally preferred for charging automobile batteries is long shunt compound generator.

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D.C. Series motor is generally preferred for cranes and hoists.

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Cumulative compound D.C. motor is preferred for elevators.

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Description :

Compare variable reluctance and permanent magnet motors.

Answer :

Variable reluctance Motor  Permanent magnet motors   The rotor is not magnetised The rotor is magnetised  High torque to inertia ratio  Low torque to inertia ratio  ... rotor has salient pole construction The rotor has mostly smooth cylindrical type of construction. 

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Description :

3 phase motor  42 hp  same ratting two motors  but pole change 2 and 4 pole   tell me difference amp of both motors

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Description :

Damper winding is provided in 3 phase synchronous motors to :

Answer :

Damper winding is provided in 3 phase synchronous motors to : provide starting torque and prevent hunting

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Description :

Generally, Crawling in squirrel cage induction motors is tendency to run stably at speeds as low as (A) One-third of their synchronous speed (B) One-fifth of their synchronous speed (C) One-seventh of their synchronous speed (D) One-ninth of their synchronous speed

Answer :

Generally, Crawling in squirrel cage induction motors is tendency to run stably at speeds as low as One-seventh of their synchronous speed

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Answer :

The capacitors used in single-phase capacitor motors have no polarity marking.

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Most of the fractional horsepower motors have either plain or sleeve bearings.

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In a capacitor start and run motors the function of the running capacitor in series with the auxiliary winding is to improve power factor.

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In capacitor start single-phase motors current in the starting winding leads the voltage.

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Description :

What is the difference between synchronous and asynchronous motors?

Answer :

The motor which rotates at constant speed is called synchronous motor. And that constant speed is called as synchronous speed.  And the motor which does not rotates at constant speed are called asynchronous motor. Asynchronous motor is also called as Induction motor.

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