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Answer :

For handling greater currents induction wattmeters are used in conjunction with current transformers.

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Last Answer : The stator of phase shifting transformer for use in conjunction with an A.C. potentiometer usually has a two-phase winding.

Last Answer : In a single phase power factor meter the phase difference between the currents in the two pressure coils is exactly 90°.

Description : State starters used for i) 3-Ph squirrel cage induction motor (3HP) ii) D.C. motor 

Last 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 

Description : The range of frequencies used in induction heating is :  (A) 0-25 Hz  (C) less than 200 Hz  (B) 50 to 100 Hz  (D) more than 1 kHz

Last Answer : The range of frequencies used in induction heating is : more than 1 kHz

Last Answer : The repulsion-start induction-run motor is used because of high starting torque.

Description : Explain following techniques related to energy conservation in transmission and distribution system. (i) By balancing phase currents (ii) Variable technical losses (I2R losses).

Last Answer : (i) Balancing Phase currents: Proper (healthy balanced) three phase loads always draw equal currents in all lines but single phase loads in the 3 phase 4 wire system or loads connected between two ... . 11) Minimize I2R losses. 12) Balance the load currents. 13) Regulate the system voltages.

Description : The transient currents are associated with the?

Last Answer : The transient currents are associated with the changes in the stored energy in the inductors and capacitors.

Description : Eddy currents are induced in the pole shoes of a D.C. machine due to?

Last Answer : Eddy currents are induced in the pole shoes of a D.C. machine due to relative rotation between field and armature.

Last Answer : Interruption of large currents by relay requires arc suppressing blow out coils, wide separation of the opened contacts, high speed opening of contacts.

Description : An induction type energy meter is found to run fast. Correction for this error can be made by  (A) Over-load compensation. (B) Voltage compensation. (C) Moving the brake magnet away from the centre of the disc. (D) Moving the brake magnet towards the centre of the disc.

Last Answer : An induction type energy meter is found to run fast. Correction for this error can be made by Moving the brake magnet away from the centre of the disc.

Last Answer : An induction wattmeter can be used for A.C. 

Last Answer : Induction type single phase energy meters measure electric energy in kWh.

Last Answer : An induction meter can handle current up to 100 A.

Description : SINGLE PHASE INDUCTION MOTORS MCQ

Last Answer : 101. After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on (a) running winding (b) rotor winding (c) field winding (d) compensating winding Ans: a ... motor is usually reduced by using (a) gearing (b) belts (c) brakes (d) chains Ans: a

Description : THREE PHASE INDUCTION MOTORS MCQ

Last Answer : 101. Insertion of resistance in the stator of an induction motor (a) increases the load torque (b) decreases the starting torque (c) increases the starting torque (d) none of the above Ans: b

Description : Explain the working principle of induction motor. 

Last Answer : Working principle of induction motor: * When the motor is excited with three-phase supply, three-phase stator winding carries three-phase currents & produces a rotating magnetic field of constant magnitude and ... , which tend to move the rotor in the same direction as the rotating magnetic field. 

Description : Explain the activities carried out during weekly maintenance of 3 ph. Induction motor. 

Last Answer : Activities Carried out During Weekly Maintenance of 3 ph. Induction Motor:  1) Check belt tension. In cases where this is excessive it should immediately be reduces and in the case of sleeve ... and cooled by oil mist systems its important to check the oil mist flow paths/pressure components.

Description : State the function of following parts in Induction motor. (i) Stator (ii) Slip rings

Last Answer : Name of part Function Stator 1) Stator frame supports the core, terminal box and protects the inner parts. 2) Stator core houses stator winding. 3) Stator winding ... ) Provides facility to connect external resistance to rotor circuit through brushes for starting and control.

Description : Electro Magnetic Induction

Last Answer : Electro Magnetic Induction

Description : List the energy conservation technique in induction motor. 

Last Answer : Following are the list of energy conservation techniques in electrical motors: 1) Reduction in iron losses by using low loss silicon steel core material laminated to thinner dimension. 2) Using bigger length ... at light load. 13) By rewinding in induction motor 14) By motor survey

Description : With a neat sketch give the working of shaded pole induction motor.

Last Answer : Explanation: It has squirrel cage rotor and salient pole stator. The stator poles are shaded partially by short circuited conductor band to create the phase difference between the fluxes emerging from shaded ... rotating magnetic field in the air-gap and torque is exerted on the squirrel cage rotor.

Description : What will happen if the induction motor runs at synchronous speed ?

Last Answer : Since there is always slip present in rotor it cannot run at synchronous speed no current will be developed hence no torque will developed

Description : Define Slip of Induction Motor.

Last Answer : Slip: It is the ratio of relative speed of rotor (difference between synchronous speed and rotor speed) to the synchronous speed of rotating magnetic field.  Slip = (NS – N) / NS  where , NS = synchronous speed, N = speed of rotor

Description : Enlist any four advantages of induction heating. 

Last Answer : Advantages of Induction heating https://youtu.be/RcdH_74VJz0

Description : Explain the working of a single phase capacitor start induction motor. 

Last Answer : Single phase capacitor start induction motor https://youtu.be/31lvvzU5Puc

Description : State any four advantages of three phase induction motor. 

Last Answer : Advantages of three phase induction motor https://youtu.be/27OIOCKN05U

Description : With a neat diagram explain doubly fed induction generator (DFIG). 

Last Answer : Diagram of Doubly fed induction generator (DFIG):  Explanation :-  DFIG can feed power through the stator as well as rotor to the grid. The stator is directly connected to the fixed frequency ... voltage is 690 V AC. So it must be step up to 33 KV to connect to power grid.  

Description : Explain Squirrel Cage Induction Generator (SCIG) and also draw a diagram. 

Last Answer : Explanation (Operation):- In this system gearbox is used to increase the speed of high speed shaft as per design. IG require reactive power for excitation. Rotor of SCIG is ... , variable voltage output of the generator into the fixed frequency, fixed voltage output required for grid. 

Last Answer : Energy conservation technique in induction motor by minimizing idle and redundant running of motor: 1) Loss of energy as the no load power drawn is approximately about 12% to 16% of rated ... to unnecessary line losses. 4) Reduction in overall system energy efficiency over period of time.

Description : State and explain any four factors governing selection of induction motor.

Last Answer : The factors governing the selection of Induction motor: 1) Load torque required at normal speed matches with available torque of motor. 2) Break down torque or pull out torque or maximum torque ... If selecting energy efficient motor the cost benefit analysis over the long run must be worked out.

Description : Explain energy conservation technique “by improving power quality” for induction motor.

Last Answer : Energy conservation method in induction motor by improving power quality: Electrical energy can be conserved by improving the power quality. It can be achieved by avoiding voltage unbalance, maintaining ... losses can be minimized by using harmonic filter thus reducing the harmonics in the system.

Description : Split phase induction motor

Last Answer : Split phase induction motor : There are two windings used in split phase induction motor. It is a type of single-phase induction motor. There are two winding one is called main winding and ... motor have low starting torque it is used for small fans, blowers, centrifugal pumps, grinders etc.

Description : State the function and shape of following parts used in induction type energy meter: i) Series magnet ii) Shunt magnet iii) Al disc iv) Brake magnet

Last Answer : i) Series magnet: produce flux proportional to current (load current) of circuit and interact in the aluminum disc with flux produced by voltage magnet for torque production. Its shape is like letter U.  ii) ... : brakes the motion of the aluminum disc or slows it down. Its shape is like letter C. 

Description : Draw a neat sketch of 1-ph induction type energy meter and write operating principle of it. 

Last Answer : Operating Principal:- The disc is placed between the two-flux due to pressure coil and flux due to current coil, which will set up torque on the disc which is proportional to power causing the ... is proportional to voltage, the second carries a current coil so its flux is proportional to current.

Description : List any four errors in induction type energy meter. Give method of compensation for each.

Last Answer : Errors in Induction Type Energy Meter with their Compensation:  1) Error due to friction: This error can be compensated by the additional shading band provided on the shunt electromagnet.  2) Phase ... error: This error can be compensated by providing a flux diverter' to the current magnet. 

Description : 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 ... the outer high resistance winding. (D) Large current flows through the inner low resistance winding.

Last Answer : In a double squirrel cage induction motor, good starting torque is produced as Large current flows through the outer high resistance winding.

Description : A change of 4% in the supply voltage to an induction motor will produce a change of approximately

Last Answer : A change of 4% in the supply voltage to an induction motor will produce a change of approximately 8% in the rotor torque

Description : The rotor impedance of a slip ring induction motor is (0.1 + j0.6)Ohm/ ph . The resistance/ph to be inserted into rotor to get maximum torque at starting should be

Last Answer : The rotor impedance of a slip ring induction motor is (0.1 + j0.6)Ohm/ ph . The resistance/ph to be inserted into rotor to get maximum torque at starting should be 0.5 Ohm

Description : In an induction motor if the flux density is reduced to one-half, of its normal value then the torque will  (1) reduce to one-half (2) reduce to one-fourth (3) remain unchanged (4) increase four times

Last Answer : In an induction motor if the flux density is reduced.to one-half, of its normal value then the torque will reduce to one-fourth

Description : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque  (1) Decreases (2) Increases (3) Remains constant (4) None of the above

Last Answer : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque Increases 

Description : Torque developed by a three-phase, 400V, induction motor is 100 N -m. If the applied voltage is reduced to 200-V, the d'veloped torque will be

Last Answer : Torque developed by a three-phase, 400V, induction motor is 100 N -m. If the applied voltage is reduced to 200-V, the d'veloped torque will be 25 N -m

Description : The slip of 400 V, three phase, 4 -pole induction motor when rotating at 1440 rpm is 

Last Answer : The slip of 400 V, three phase, 4 -pole induction motor when rotating at 1440 rpm is 4 percent

Description : A 400 V, 50 Hz three-phase induction motor rotates at 1440 rpm on full -load. The motor is wound for

Last Answer : A 400 V, 50 Hz three-phase induction motor rotates at 1440 rpm on full -load. The motor is wound for 4 poles

Description : In a single-phase induction motor, the operating direction is determined by the ________ A) Rotor B) Stator C) Starting circuit D) None of these

Last Answer : In a single-phase induction motor, the operating direction is determined by the Starting circuit

Description : What is the slip (as a percentage) when a 6 pole single phase induction motor operating on 220 V and 60 Hz is rotating at speed of 1140 rpm? A) 60% B) 5% C) 10% D) None of these

Last Answer : What is the slip (as a percentage) when a 6 pole single phase induction motor operating on 220 V and 60 Hz is rotating at speed of 1140 rpm? A) 60% B) 5% C) 10% D) None of these

Description : In the induction type directional over current relay, when a short-circuit occurs in the circuit (A) power flows in reverse direction (B) power flows in normal direction (C) directional power element does not operate (D) over current element is not energized

Last Answer : In the induction type directional over current relay, when a short-circuit occurs in the circuit power flows in reverse direction

Description : In a split-phase induction motor, the resistance/reactance ratios of windings are such that (A) current in the auxiliary winding leads the current in the main winding (B) current in the ... (C) both windings develop the same starting torque (D) both windings develop high starting current

Last Answer : In a split-phase induction motor, the resistance/reactance ratios of windings are such that current in the auxiliary winding leads the current in the main winding

Description : In a single-phase induction motor when the rotor is stationary and voltage is applied to the stator, then (A) the flux is constant (B) the flux first decreases and then increases in ... increases and decreases in the opposite direction with the same magnitude (D) current flows through the rotor

Last Answer : In a single-phase induction motor when the rotor is stationary and voltage is applied to the stator, then the flux first decreases and then increases in the same direction

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

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

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

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