Answer :
D.C. shunt motors are used for driving machine tools.
asked
Mar 20, 2018
by
anonymous
Description : State starters used for i) 3-Ph squirrel cage induction motor (3HP) ii) D.C. motor
Answer :
Name the starters used for following motors : i) 3 H.P. 3-Ph squirrel cage I.M: i) DOL starter OR ii) Star-Delta Starter OR ii) Auto transformer starter OR iii) Soft start starter. ii) D.C Shunt Motor : 1) Armature resistance starter (Three Point Starter) OR 2) Four Point Starter
asked
Sep 18, 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
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 : What are the five types of single phase motors used in the industry?
asked
Mar 15, 2018
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 :
The capacitors used in single-phase capacitor motors have no polarity marking.
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 D.C. shunt motors as load is reduced the speed will remain almost constant.
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 :
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.
asked
Mar 20, 2018
by
anonymous
Description : What is the advantage of using soft starters?
asked
Mar 15, 2018
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 :
During rheostat braking of D.C. series motors motor is run as a generator.
asked
Mar 20, 2018
by
anonymous
Answer :
In D.C. machines fractional pitch winding is used to reduce the sparking.
asked
Mar 20, 2018
by
anonymous
Answer :
The type of D.C. motor used for shears and punches is cumulative compound D.C. motor.
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 : 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
Answer :
In a dc machine, interpoles are used to neutralize the effect of armature reaction in the interpolar region
asked
Apr 29, 2018
by
anonymous
Description : Explain selection of starters for Industrial Installation.
Answer :
selection of starters for Industrial Installation: Every motor must be provided with a starter to start and stop the motor. It shall be within the sight of a person at the motor. It shall be so arranged as ... -Auto transformer starter Slip ring I.M.------------------Rotor resistance starter
asked
Sep 20, 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 :
A direct online starter is used for starting motors up to 5 H.P.
asked
Mar 20, 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 : 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 :
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 :
Synchronous motors are generally not self-starting because the direction of instantaneous torque reverses after half cycle.
asked
Mar 20, 2018
by
anonymous
Answer :
The voltage used for suburban trains in D.C. system is usually 600 to 750 V.
asked
Mar 22, 2018
by
anonymous
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
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 :
Most of the fractional horsepower motors have either plain or sleeve bearings.
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
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 : How is a thyristor used to convert AC to DC?
asked
Mar 19, 2018
by
anonymous
Description : Which type of starter is used to start the DC motor?
asked
Mar 15, 2018
by
anonymous
Description : Why DC motor is used for traction?
asked
Mar 11, 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
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 :
The standard full-load power factor ratings for synchronous motors are unity or 0.8 leading.
asked
Mar 20, 2018
by
anonymous
Answer :
Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be cumulatively compounded.
asked
Mar 20, 2018
by
anonymous
Description : 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
Answer :
Aluminium is not used as winding wire for the armature of a dc machine because (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
by
anonymous
Answer :
Sparking, is discouraged in a D.C. motor because commutator gets damaged.
asked
Mar 20, 2018
by
anonymous
Answer :
For starting a D.C. motor a starter is required because it limits the starting current to a safe value.
asked
Mar 20, 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 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 : 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
Answer :
The range of efficiency for shaded pole motors is 5% to 35%.
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
Answer :
For power factor correction, synchronous motors operate at no-load and greatly over-excited fields.
asked
Mar 20, 2018
by
anonymous