What are the materials used to manufacture the brushes for slip rings of an induction motor?

What are the materials used to manufacture the brushes for slip rings of an  induction motor?
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1 Answer

Answer :

A:The slip rings are made of brass and phosphor bronze. The brushes are made of metal graphite which is an alloy of copper and carbon.
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Related questions

Slip ring induction motor advantages and disadvantages compared to squirrel cage motors?

Description : Slip ring induction motor advantages and disadvantages compared to squirrel cage motors?

Last Answer : Advantages: High starting torque with low starting current Smooth acceleration under heavy loads No abnormal heating during starting Good running characteristics after external rotor resistances are cut out ... cage motors The speed regulation is poor when run with resistance in the rotor circuit

Mention different types of speed control of slip ring induction motor?

Description : Mention different types of speed control of slip ring induction motor?

Last Answer : a) By changing supply frequency b) By changing the number of stator poles c) By rotor rheostat control d) By operating two motors in cascade

What is the purpose of connecting external resistors to slip ring Induction motor?

Description : What is the purpose of connecting external resistors to slip ring Induction motor?

Last Answer : It increases starting torque and decreases starting current.

What are slip rings?

Description : What are slip rings?

Last Answer : The slip rings are made of copper alloys and are fixed around the shaft insulating it. Through these slip rings and brushes the rotor winding can be connected to external circuits.

Name the materials used to insulate the laminations of the core of induction motor.

Description : Name the materials used to insulate the laminations of the core of induction motor.

Last Answer : The materials used to insulate the laminations are kaolin and varnish.

The reversal of an AC, three-phase, induction motor is accomplished by ______________. A. changing all three motor leads B. reversing the position of the slip rings C. interchanging any two of the three motor leads D. interchanging any two brushes

Description : The reversal of an AC, three-phase, induction motor is accomplished by ______________. A. changing all three motor leads B. reversing the position of the slip rings C. interchanging any two of the three motor leads D. interchanging any two brushes

Last Answer : Answer: C

In an induction motor, rotor currents are circulated in the rotor by _____________. A. slip rings and brushes B. an armature and brushes C. inductive reaction of the rotating stator field D. external variable resistors

Description : In an induction motor, rotor currents are circulated in the rotor by _____________. A. slip rings and brushes B. an armature and brushes C. inductive reaction of the rotating stator field D. external variable resistors

Last Answer : Answer: C

How the slip ring motor is started?

Description : How the slip ring motor is started?

Last Answer : The slip ring motor is started by using rotor resistance starter. The starter consists of star connected resistance to slip rings. While starting the full resistance is included in the rotor circuit to ... running condition the slip rings are shorted and so it is equivalent to squirrel cage rotor.

What are the advantages of slip ring motor over squirrel cage motor?

Description : What are the advantages of slip ring motor over squirrel cage motor?

Last Answer : 1. The starting torque can be varied by adding resistance to rotor. 2. The speed of the machine can be varied by injecting an emf through slip rings to the rotor.

Explain the operation of induction motor in simple words?

Description : Explain the operation of induction motor in simple words?

Last Answer : Answer: When 3 phase ac supply is given to stator of the induction motor rotating magnetic field will be generated. This magnetic field (flux) cuts the stationary conductors of the rotor of ... be developed. If the torque generated is sufficient to overcome the load torque rotor starts rotating.

Why Speed Control of Induction Motor is difficult compared to DC shunt motor?

Description : Why Speed Control of Induction Motor is difficult compared to DC shunt motor?

Last Answer : Answer: Speed Control of DC shunt motor can be possible by providing resistance in the armature and field circuits and varying the resistors speed changes can be carried out over a wide range. ... employed. Care should be taken that in the process efficiency and power factor should be maintained.

Why the efficiency of the Induction motor is less compared to transformer?

Description : Why the efficiency of the Induction motor is less compared to transformer?

Last Answer : Answer: Induction motor and Transformer operates on the same principle that power is transferred to secondary by mutual induction. But in transformer, flux will be traveled from primary to ... compared to transformer which also results in less efficiency for induction motor compared to transformer.

Disadvantages of Star-Delta Starting of Induction motor?

Description : Disadvantages of Star-Delta Starting of Induction motor?

Last Answer : In Star-Delta starting induction motor stator is connected in star connection for starting after picking up speed it is connected to delta connection. When induction motor is connected in star connection ... . This also results in reduced starting torque (1/3 times compared to delta connection).

What is the condition for maximum torque in induction motor?

Description : What is the condition for maximum torque in induction motor?

Last Answer : Starting torque will be maximum when the rotor resistance / phase is equal to standstill rotor reactance / phase

Induction Motor Operating Characteristics

Description : Induction Motor Operating Characteristics

Last Answer : All torques of an induction motor, at a given slip, vary approximately as the square of the voltage applied to its terminals Low rotor resistance results in high full load speed (low slip), ... voltage), the load torque is unchanged, and the ratio of accelerating torque to load torque is reduced

why the three phase induction motor draws heavy current at starting?

Description : why the three phase induction motor draws heavy current at starting?

Last Answer : At the time of starting, the rotor speed is zero hence slip is 1, the emf induced in rotor winding is very high. Hence rotor current is also very high. The starting current is 5 to 7 times more than its full load current.

What happens if the air gap flux density in an induction motor increases?

Description : What happens if the air gap flux density in an induction motor increases?

Last Answer : The increase in air gap flux increases iron loss and hence efficiency decreases.

What would happen if a 3 phase induction motor is switched on with one phase disconnected?

Description : What would happen if a 3 phase induction motor is switched on with one phase disconnected?

Last Answer : The motor is likely to burn .

In what respect does a 1-phase Induction motor differ from a 3-phase Induction motor?

Description : In what respect does a 1-phase Induction motor differ from a 3-phase Induction motor?

Last Answer : Construction wise a plain 1-phase Induction motor is more or less similar to a 3-phase squirrel-cage Induction motor except that its stator is provided with only 1-phase winding..

Why the air gap of an induction motor is made as small as possible?

Description : Why the air gap of an induction motor is made as small as possible?

Last Answer : The mmf and the magnetizing current are primarily decided by length of air gap. If air gap is small then mmf and magnetizing current will be low, which in turn increase the value of power factor. Hence by keeping small air gap, high power factor is achieved.

List out the methods to improve the power factor of the induction motor.

Description : List out the methods to improve the power factor of the induction motor.

Last Answer : The power factor of the induction motor can be improved by reducing the magnetizing current and leakage reactance. The magnetizing current can be reduced by reducing the length of air gap. The ... stator & rotor slots, by providing short chorded winding and reducing the overhang in stator winding.

What are the advantages and disadvantages of large air gap length in induction motor?

Description : What are the advantages and disadvantages of large air gap length in induction motor?

Last Answer : Advantage: A large air gap length results in higher overload capacity, better cooling, reduction in noise and reduction in unbalanced magnetic pull. Disadvantages: The disadvantage of large air gap length is that it results in high value of magnetizing current.

Which part of induction motor has the maximum flux density? What is the maximum flux density in that part?

Description : Which part of induction motor has the maximum flux density? What is the maximum flux density in that part?

Last Answer : The teeth of the stator and rotor core will have maximum flux density. The maximum value of flux density in the teeth is 1.7 wb/m

What types of slots are preferred for the induction motor?

Description : What types of slots are preferred for the induction motor?

Last Answer : Semi enclosed slots are preferred for induction motor. It results in less air gap contraction factor giving a small value of magnetizing currents, low tooth pulsation loss and much quieter operation(less noise)

What are the different types of stator winding in induction motor?

Description : What are the different types of stator winding in induction motor?

Last Answer : The different types of stator windings are mush winding, lap winding and wave winding.

What are the advantages of 3-phase induction motor?

Description : What are the advantages of 3-phase induction motor?

Last Answer : a) It was very simple and extremely rugged, almost unbreakable construction b) Its cost is very low and it is very reliable c) It has been suffiently high efficiency .No brushes are needed and hence frictional losses are reduced d) It requires minimum of maintenance.

List out the methods of speed control of cage type 3-phase induction motor?

Description : List out the methods of speed control of cage type 3-phase induction motor?

Last Answer : a) By changing supply frequency b) By changing the number of poles c) By operating two motors in cascade

Explain why the no load current of an induction motor is much higher than that of an equivalent transformer.

Description : Explain why the no load current of an induction motor is much higher than that of an equivalent transformer.

Last Answer : In induction motor, due to the presence of the air gap, the magnetizing current that is required to set up the flux is much higher. The working component of the current has to meet the ... eddy current loss, friction and windage losses. Hence the no load current of induction motor is higher.

Why the induction motor is called asynchronous motor?

Description : Why the induction motor is called asynchronous motor?

Last Answer : Since the induction motor runs always at a speed lesser than synchronous speed, it is called asynchronous motor.

Why Induction motor is called rotating transformer?

Description : Why Induction motor is called rotating transformer?

Last Answer : Transformer has two sides: primary & secondary. Transformer transforms energy from primary to secondary by induction. Similarly, Induction motor has primary (stator) & secondary (rotor). Voltage is ... magnitude i.e. the process of induction Thus induction motor treated as a rotating transformer.

Why skewing is done in squirrel cage Induction motor?

Description : Why skewing is done in squirrel cage Induction motor?

Last Answer : i) For more uniform torque ii) Reduction in noise iii) To decrease magnetic locking tendency

State the types of Induction motor ?

Description : State the types of Induction motor ?

Last Answer : 1) Squirrel cage Induction motor 2) Wound or slip ring Induction motor.

Explain how Torque-Slip Characteristics vary when adding resistance to rotor circuit?

Description : Explain how Torque-Slip Characteristics vary when adding resistance to rotor circuit?

Last Answer : The addition of resistance to the rotor circuit does not change the value of maximum torque but it only changes the value of the slip at which the maximum torque occurs

What is the normal value of slip of an I M operating at full load?

Description : What is the normal value of slip of an I M operating at full load?

Last Answer : 3 - 5%

How the frequency of rotor emf is related to the slip in an I M?

Description : How the frequency of rotor emf is related to the slip in an I M?

Last Answer : Frequency of rotor emf/current fr=Sf

How the magnitude of rotor emf is related to the slip in an I M?

Description : How the magnitude of rotor emf is related to the slip in an I M?

Last Answer : Rotor circuit emf per phase E2’=SE2

What is Slip?

Description : What is Slip?

Last Answer : The difference between synchronous speed and rotor speed with respect to synchronous speed is called slip. S=Ns-N/Ns*100

What is slip speed?

Description : What is slip speed?

Last Answer : The difference between synchronous speed and rotor speed is called slip speed.

What are the advantages and disadvantages of Induction Motors?

Description : What are the advantages and disadvantages of Induction Motors?

Last Answer : Advantages: It is simple and rugged in construction It is relatively cheap Induction motors require less maintenance Induction motor has high efficiency and reasonably good power factor 3-phase induction ... and its speed cannot be changed easily Its starting torque is inferior to dc shunt motor

Name the tests to be conducted for predetermining the performance of 3-phase induction machine.

Description : Name the tests to be conducted for predetermining the performance of 3-phase induction machine.

Last Answer : (a) No load test (b) Blocked rotor test

A three-phase, squirrel cage, induction motor will run hot due to _____________. A. open stator coils B. high power factor C. dirty or corroded slip rings D. reversed commutating poles

Description : A three-phase, squirrel cage, induction motor will run hot due to _____________. A. open stator coils B. high power factor C. dirty or corroded slip rings D. reversed commutating poles

Last Answer : Answer: A

Which of the following physical characteristics does a wound-rotor induction motor possess that a squirrel cage motor does not? A. Slip rings B. End rings C. A centrifugal switch D. End plates

Description : Which of the following physical characteristics does a wound-rotor induction motor possess that a squirrel cage motor does not? A. Slip rings B. End rings C. A centrifugal switch D. End plates

Last Answer : Answer: A

An alternator will fail to produce line voltage as a result of _____________. A. a closed circuit breaker B. oxidized slip rings C. improperly staggered brushes D. exciter generator failure

Description : An alternator will fail to produce line voltage as a result of _____________. A. a closed circuit breaker B. oxidized slip rings C. improperly staggered brushes D. exciter generator failure

Last Answer : Answer: D

Which of the following statements represents the FIRST step in seating new brushes on slip rings? A. Wrap sandpaper around the slip rings and slide it back and forth between the brushes and the slip rings. B. Press the brushes against the slip ring with a wood block. C. Increase brush pressure and run at no load for 3 to 4 hours. D. Apply seating compound under the brushes and run at no load for 2 hours.

Description : Which of the following statements represents the FIRST step in seating new brushes on slip rings? A. Wrap sandpaper around the slip rings and slide it back and forth between the brushes and the slip rings. B. ... to 4 hours. D. Apply seating compound under the brushes and run at no load for 2 hours.

Last Answer : Answer: A

To properly seat the brushes on slip rings, you should use ____________. A. sand paper B. crocus cloth C. emery cloth D. all of the above

Description : To properly seat the brushes on slip rings, you should use ____________. A. sand paper B. crocus cloth C. emery cloth D. all of the above

Last Answer : Answer: A

In actual applications, electrical connections to 'R1-R2' of figure 'A' and to 'R1-R2- R3' of figure 'B' shown in the illustration are made by ______________. EL-0092 A. soldered contacts B. spliced and taped connections C. slip rings and brushes D. solderless crimp-on connectors

Description : In actual applications, electrical connections to 'R1-R2' of figure 'A' and to 'R1-R2- R3' of figure 'B' shown in the illustration are made by ______________. EL-0092 A. soldered contacts B. spliced and taped connections C. slip rings and brushes D. solderless crimp-on connectors

Last Answer : Answer: C

Which of the following statements is true concerning all three-phase alternators? A. Each has three separate but identical armature windings acted on by one system of rotating magnets. B. Each has one armature winding acted on by three identical but separate systems of rotating magnets. C. All three-phase alternators are designed to operate with a 0.8 leading power factor. D. The three phases always provide power to the load through three sets of slip rings and brushes.

Description : Which of the following statements is true concerning all three-phase alternators? A. Each has three separate but identical armature windings acted on by one system of rotating magnets. B. Each has one ... The three phases always provide power to the load through three sets of slip rings and brushes.

Last Answer : Answer: A

In an AC generator, direct current from a separate source is passed through the windings of the rotor _____________. A. by means of slip rings and brushes B. by means of a commutator C. by means of rotating bar magnet D. to minimize the danger of arc over

Description : In an AC generator, direct current from a separate source is passed through the windings of the rotor _____________. A. by means of slip rings and brushes B. by means of a commutator C. by means of rotating bar magnet D. to minimize the danger of arc over

Last Answer : Answer: A

Voltage generated by most AC generators is fed from the machine to the bus by means of ____________. A. brushes on a commutator B. brushes on slip rings C. slip rings on a commutator D. direct connections from the stator

Description : Voltage generated by most AC generators is fed from the machine to the bus by means of ____________. A. brushes on a commutator B. brushes on slip rings C. slip rings on a commutator D. direct connections from the stator

Last Answer : Answer: D