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Is induction heating safe?
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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

Answer :

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

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81 views 1 answer
Description :

Enlist any four advantages of induction heating. 

Answer :

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

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Description :

Answer :

Yes, Induction heating is used for both magnetic and non-magnetic materials.

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Description :

What is a safe distance from power lines?

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Description :

The frequencies and voltage used in Dielectric heating are (A) 10 – 30 MHz, upto 25 kV (B) 50 – 60 Hz, upto 25 kV (C) 10 – 30 MHz, upto 100 V (D) 50 – 60 Hz, 110 V – 230 V

Answer :

The frequencies and voltage used in Dielectric heating are 10 – 30 MHz, upto 25 kV

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98 views 1 answer
Description :

What is meant by resistance heating?

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Description :

What is meant by dielectric heating?

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Description :

Select insulating materials for following parts : (i) Insulation between heating element and base plate of electric iron. (ii) Insulation used over copper or aluminium conductor used for making coils. (iii) Transformer bushings. (iv) Insulation between transmission line and pole.

Answer :

Parts Insulating Materials  Insulation between heating element and base plate of electric iron. Mica Insulation used over copper or aluminium conductor used for making coils.  ... Transformer bushings Porcelain  Insulation between transmission line and pole. Porcelain

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85 views 1 answer
Description :

State advantages of electric heating over other types of heating methods.

Answer :

Advantages of Electric heating over the other types of heating methods: 1. It can be put into service immediately. 2. No standby losses. 3. High efficiency. 4. More economical ... low attention and supervision. 14. Protection against overheating can be provided by suitable switch gear. 

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154 views 2 answers
Description :

_______ is used for heating non -conducting materials.  (1) Eddy current heating (2) Arc heating (3) Induction heating (4) Dielectric heating

Answer :

Dielectric heating is used for heating non -conducting materials. 

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2.7k views 1 answer
Description :

Answer :

In order that current should flow without causing excessive heating or voltage drop, the relay contacts should have low contact resistance, be clean and smooth, be of sufficient size and proper shape.

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119 views 1 answer
Description :

How do induction heaters work?

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Description :

For heating a magnetic material using induction heating, the hysteresis and eddy current losses are respectively proportional to (a) f and f 2 (b) f 2 and f (c) f and f (d) none of the above 

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73 views 0 answers
Description :

For induction heating, which of the following is abnormally high?  A)Voltage B) Current C) Frequency D) Phase angle

Answer :

For induction heating, which of the following is abnormally high?  A)Voltage B) Current C) Frequency D) Phase angle

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220 views 1 answer
Description :

Explain the working principle of induction motor. 

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. 

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99 views 1 answer
Description :

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

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.

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100 views 1 answer
Description :

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

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.

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80 views 1 answer
Description :

Electro Magnetic Induction

Answer :

Electro Magnetic Induction

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117 views 1 answer
Description :

List the energy conservation technique in induction motor. 

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

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87 views 1 answer
Description :

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

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.

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148 views 2 answers
Description :

Define Faraday’s first law of electromagnetic induction. 

Answer :

Faraday’s First Law: Whenever a changing magnetic flux links with a conductor, an emf is induced in that conductor.  OR  When a conductor cuts across magnetic field, an emf is induced in that conductor.

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86 views 1 answer
Description :

Explain with neat circuit diagrams the procedures to perform no load and blocked rotor tests on three phase induction motor.

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Description :

Explain the need and steps to conduct the reduced voltage running up test on the three phase induction motor.

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Description :

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

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

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98 views 3 answers
Description :

Define Slip of Induction Motor.

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

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39 views 1 answer
Description :

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

Answer :

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

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213 views 2 answers
Description :

State any four advantages of three phase induction motor. 

Answer :

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

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113 views 2 answers
Description :

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

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.  

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5.1k views 1 answer
Description :

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

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. 

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2.7k views 2 answers
Description :

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.

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434 views 1 answer
Description :

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

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.

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2.7k views 1 answer
Description :

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

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.

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3.0k views 2 answers
Description :

Split phase induction motor

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.

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190 views 1 answer
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 

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128 views 1 answer
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

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. 

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94 views 1 answer
Description :

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

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.

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95 views 1 answer
Description :

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

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. 

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1.1k views 1 answer
Description :

State Faraday's law of electromagnetic induction.

Answer :

First Law: - Whenever change in the magnetic flux linked with a coil or conductor, an EMF is induced in it. OR Whenever a conductor cuts magnetic flux, an EMF is induced in conductor.  Second Law: ... of induced EMF is directly proportional to (equal to) the rate of change of flux linkages.

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167 views 3 answers
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 resistance winding. (C) Small current flows through the outer high resistance winding. (D) Large current flows through the inner low resistance winding.

Answer :

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

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103 views 1 answer
Description :

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

Answer :

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

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307 views 1 answer
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

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

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136 views 1 answer
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

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

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267 views 1 answer
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

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 

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135 views 1 answer
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

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

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118 views 1 answer
Description :

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

Answer :

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

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238 views 1 answer
Description :

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

Answer :

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

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172 views 1 answer
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

Answer :

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

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84 views 1 answer
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

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

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87 views 1 answer
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

Answer :

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

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91 views 1 answer
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 auxiliary winding lags the current in the main winding (C) both windings develop the same starting torque (D) both windings develop high starting current

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

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88 views 1 answer
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