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.
asked
Apr 28, 2018
by
anonymous
Answer :
D.C. shunt motors are used for driving machine tools.
asked
Mar 20, 2018
by
anonymous
Description : Why DC motor is used for traction?
asked
Mar 11, 2018
by
anonymous
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
asked
Apr 26, 2018
by
anonymous
Answer :
During rheostat braking of D.C. series motors motor is run as a generator.
asked
Mar 20, 2018
by
anonymous
Answer :
Differentially compound D.C. motors can find applications requiring low starting torque.
asked
Mar 20, 2018
by
anonymous
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.
asked
Sep 3, 2019
by
anonymous
Answer :
When two D.C. series motors are connected in parallel, the resultant speed is normal speed.
asked
Mar 20, 2018
by
anonymous
Answer :
Starters are used with D.C. motors because to restrict armature current as there is no back e.m.f. while starting.
asked
Mar 20, 2018
by
anonymous
Answer :
In case of conductively compensated D.C. series motors, the compensating winding is provided in series with armature winding.
asked
Mar 20, 2018
by
anonymous
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.
asked
Mar 20, 2018
by
anonymous
Answer :
In D.C. shunt motors as load is reduced the speed will remain almost constant.
asked
Mar 20, 2018
by
anonymous
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
asked
Apr 29, 2018
by
anonymous
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
asked
Aug 17, 2019
by
anonymous
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
asked
May 7, 2020
by
anonymous
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
asked
May 1, 2018
by
anonymous
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
asked
Apr 28, 2018
by
anonymous
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.
asked
Apr 30, 2018
by
anonymous
Answer :
An ideal traction system should have easy speed control, high starting tractive effort, equipment capable of with standing large temporary loads.
asked
Mar 22, 2018
by
anonymous
Description : Which motor is used in traction system?
asked
Mar 11, 2018
by
anonymous
Description : What is the traction system?
asked
Mar 11, 2018
by
anonymous
Answer :
MOSFET have high current losses due to High on state resistance. Hence MOSFET is used for low power applications.
asked
Sep 22, 2017
by
anonymous
Description : 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.
asked
Jul 30, 2019
by
anonymous
Answer :
As hysteresis motors are free from mechanical and magnetic vibrations therefore these are considered as suitable for sound equipment.
asked
Mar 20, 2018
by
anonymous
Answer :
The standard full-load power factor ratings for synchronous motors are unity or 0.8 leading.
asked
Mar 20, 2018
by
anonymous
Description : 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
asked
May 25, 2018
by
anonymous
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.
asked
Aug 17, 2019
by
anonymous
Description : Stepper motors are used in (1) printers (2) lifts (3) amplifiers (4) oscillators
Answer :
Stepper motors are used in printers
asked
Apr 29, 2018
by
anonymous
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
asked
Apr 28, 2018
by
anonymous
Answer :
Synchronous motors are generally not self-starting because the direction of instantaneous torque reverses after half cycle.
asked
Mar 20, 2018
by
anonymous
Description : The efficiencies of transformers compared with that of electric motors of the same power are?
Answer :
Transformers have high efficiency than the same ratted motors
asked
Mar 19, 2018
by
anonymous
Description : What are the five types of single phase motors used in the industry?
asked
Mar 15, 2018
by
anonymous
Description : 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.
asked
Aug 17, 2019
by
anonymous
Description : 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
asked
May 8, 2018
by
anonymous
Answer :
A direct online starter is used for starting motors up to 5 H.P.
asked
Mar 20, 2018
by
anonymous
Answer :
The range of efficiency for shaded pole motors is 5% to 35%.
asked
Mar 20, 2018
by
anonymous
Answer :
For power factor correction, synchronous motors operate at no-load and greatly over-excited fields.
asked
Mar 20, 2018
by
anonymous
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
asked
Apr 27, 2020
by
anonymous
Answer :
D.C. generator generally preferred for charging automobile batteries is long shunt compound generator.
asked
Mar 20, 2018
by
anonymous
Answer :
D.C. Series motor is generally preferred for cranes and hoists.
asked
Mar 20, 2018
by
anonymous
Answer :
Cumulative compound D.C. motor is preferred for elevators.
asked
Mar 20, 2018
by
anonymous
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.
asked
Jul 30, 2019
by
anonymous
Description : 3 phase motor 42 hp same ratting two motors but pole change 2 and 4 pole tell me difference amp of both motors
asked
Jul 24, 2019
by
ZAHID
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
asked
Apr 29, 2018
by
anonymous
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
asked
Apr 28, 2018
by
anonymous
Answer :
The capacitors used in single-phase capacitor motors have no polarity marking.
asked
Mar 20, 2018
by
anonymous
Answer :
Most of the fractional horsepower motors have either plain or sleeve bearings.
asked
Mar 20, 2018
by
anonymous
Answer :
In a capacitor start and run motors the function of the running capacitor in series with the auxiliary winding is to improve power factor.
asked
Mar 20, 2018
by
anonymous
Answer :
In capacitor start single-phase motors current in the starting winding leads the voltage.
asked
Mar 20, 2018
by
anonymous
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.
asked
Mar 15, 2018
by
anonymous