An electric motor in which both stator field and rotor rotates with same speed is called synchronous motor.
The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as?
Which rotor is use for high speed in turbo alternators?
Non-salient pole rotor is used for high speed in turbo alternators.
Salient pole rotor is use for which speed?
Salient pole rotor is use for low and medium speed prime movers.
The ability of materials to become polarized under an applied electric field is called _______ A) Ferroelectricity B) Paraelectricity C) Polectricity D) None of these
The ability of materials to become polarized under an applied electric field is called Paraelectricity
A 400 V, 50 Hz three-phase induction motor rotates at 1440 rpm on full -load. The motor is wound for
A 400 V, 50 Hz three-phase induction motor rotates at 1440 rpm on full -load. The motor is wound for 4 poles
When the armature of a D.C. motor rotates, e.m.f. induced is back e.m.f.
If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will stop.
Explain with neat circuit diagrams the procedures to perform no load and blocked rotor tests on three phase induction motor.
State the function of following parts in Induction motor. (i) Stator (ii) Slip rings
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.
The purpose of stator winding in the compensated repulsion motor is to improve power factor and provide better speed regulation.
How can a magnetic field be used to generate an electric current?
Magnetic field can be used to generate electric current on a condition that it is on a rate of changing magnetic flux. (Faraday's law)
If the field of synchronous motor is under excited, power factor will be?
If the field of synchronous motor is under excited, power factor will be lagging.
Synchronous motor always runs at which speed?
Synchronous motor always runs at synchronous speed.
The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as?
The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as pull-in torque.
The operating speed of a synchronous motor can be changed to new fixed value by changing frequency.
If we change the excitation of synchronous machine will it affect on motor speed?
No, If we change the excitation of synchronous machine it will not affect on motor speed.
Briefly describe the electric field of a static charge.
The electric field inside a hollow conducting sphere ________ A) Depends on the diameter of the sphere B) Varies according to the direction of earth’s magnetic poles C) Is zero D) None of these
The electric field inside a hollow conducting sphere Is zero
MOSFET uses the electric field of?
MOSFET uses the electric field of gate capacitance.
Is electric potential zero when electric field is zero?
Yes .If electric field is zero then electric potential is zero , not even one.
What is the direction of the induced electric field?
It is in opposite direction to the one that produced it.
Can the electric field between two positive charges be zero?
It can only if they have equal charges.
What is the direction of the electric field?
Electric field is at right angle widh flow of current (right hand rule).
In a hysteresis motor, the rotor must have retentivity.
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
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
Ratio of the rotor reactance X to the rotor resistance R for a two-phase servo motor (A) is equal to that of a normal induction motor (B) is less than that of a normal induction motor (C) is greater than that of a normal induction motor (D) may be less or greater than that of a normal induction motor
Locked rotor current of a shaded pole motor is slightly more than full load current.
The rotor of a hysteresis motor is made of chrome steel.
The rotor developed by a single-phase motor at starting is zero.
What is the rotor of a motor?
Rotor is the rotating or moving part in motor and generator.
For the same H.P. rating and full load speed, following motor has poor starting torque differentially compounded.
The speed/load characteristics of a universal motor is same as that of D.C. series motor.
If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens this will make armature to take heavy current, possibly burning it.
In a shaded pole single-phase motor, the revolving field is produced by the use of shading coils.
The synchronous speed of an 8 pole induction motor supplied power from a 50 Hz source will be ?
Ns equals f/pair pole 50/4 - 12.5
If the field of a D.C. shunt motor gets opened while motor is running the motor will attain dangerously high speed.
Field control of DC motor
Series motor has the poorest speed control.
Which motor has the best speed regulation?
The power mentioned on the name plate of an electric motor indicates the output power available at the shaft.
What is an electric motor drive?
How does an electric motor works?
In the electric motor there are two types of part 1)moving and 2)stationary In stationary part containing field winding whis use to provide uniform maganetic field it at inner side of yoke In moving ... on it and this force is from all direction we can say it is torque.and motor armature rotates
What is the use of an electric motor?
Electrical motors are use for converting electrical energy to mechanical energy. It may be use in fans, pumps, washing machine, cranes, trains, factories, industries etc.
In variable speed motor a weaker commutating field is needed at low speed than at high speed.
In a D.C. shunt motor, speed is independent of armature current.
In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will run as induction motor.
If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in damage to the starting winding.
The stator of phase shifting transformer for use in conjunction with an A.C. potentiometer usually has a two-phase winding.
Speed control of the motor using TRIAC
Speed control of the motor using TRIAC: This basic phase triggering circuit uses the triac in series with the motor across an AC sinusoidal supply. The variable resistor, VR1 is used ... meaning that it may not trigger at the exact same point for each positive and negative half cycle.
Why does the speed of a DC shunt motor decrease as the load increases?
Because if the load is increasing then the torque must also be increase. If not then the speed of motor will decrease.