A resistance split-phase induction motor is used for .............
At starting the line current of a capacitor-start induction motor is ............ the normal full-load current.
A capacitor-start, capacitor -run motor has.............
The direction of rotation of shaded -pole motor depends upon ............
A ceiling fan of 1400 mm sweep will have motor rating of
The best suited motor to drive 1/4 h.p fan in a hospital ward would be ........... motor.
The washing machine generally employs ........motors.
The best suited motor to drive 3/4 h.p. aircompressor would be .......... motor.
In capacitor start single phase induction motor, the current in the
As compared to capacitor -start induction motors or split-phase motors, a permanent split capacitor motor has lower
In a split-phase inductor motor, the two stator windings
The split phase induction motor has two windings, the main winding and the auxiliary winding. These windings are displaced in space by 90o electrical. The auxiliary winding has higher current ratio between resistance and reactance, by designing it at a higher current density.
What happens when the centrifugal switch in the starting winding of a single - phase induction motor fails to open ?
Which of the following types of a.c. motors are synchronous type ?
A reluctance motor runs at
The rotor operates at synchronous speeds without current-conducting parts. Rotor losses are minimal compared to those of an induction motor.
Once started at synchronous speed, the motor can operate with sinusoidal voltage. Speed control requires a variable-frequency drive.
In ac series motor the purpose of providing compensating winding is to
A reluctance motor is a type of electric motor that induces non-permanent magnetic poles on the ferromagnetic rotor. The rotor does not have any windings. It generates torque through magnetic reluctance.
A. Reluctance motors are not self starting
B. Reluctance motors start as induction motor and runs as synchronous motors
C. Reluctance motors needs no DC excitation
A d.c. series motor is accidentally connected to single phase supply. The torque produced will be
In DC series motor, the AC currents through the field and armature winding will be unidirectional by commutator and brushes. So torque will be unidirectional but pulsating due to AC.
Which of the following motors is preferred for tape recorder ?
Which of the following motors has the largest starting torque ?
A Capacitor Start Motors is a single phase Induction Motor that employs a capacitor in the auxiliary winding circuit to produce a greater phase difference between the current in the main and the auxiliary windings. Due to greater phase difference capacitor Start motors have very high starting torque for a single-phase AC motor.
If the capacitor of a single-phase motor is short-circuited
The capacitor helps the motor to get starting torque by phase splitting. If the capacitor is short circuited,there will be no starting torque and as single phase induction motor is not self starting,it will not start rotating. single phase induction motor is not self starting. capacitor is used to start the motor.
The voltage actually used for setting up of the useful flux in the air gap of 3- phase induction motor is
A balanced 3- phase induction motor runs at slip s. If ws is its synchronous speed, what is the relative speed between the stator mmf and rotor mmf.
In an induction motor the slip will be negative when
Negative slip indicates that the motor is running above synchronous speed. This can happen only when it is driven by a prime mover. This motor becomes an induction generator. For it to generate, it must be connected to a power supply, from where it can draw magnetising current.
A voltmeter gives 120 oscillations per minute when connected to the rotor of an induction motor. The frequency is 50 Hz. The slip of the motor is
Rotor voltage frequency = 120/f = 2 Hz
Rotor voltage frequency = S x supply frequency
2 = S x 50
S = 2/50 = 0.04 = 4%
The frequency of rotor currents at standstill is equal to
When the motor is stationary,rotor conductors are being cut by rotating flux at synchronous speed.therefore,the frequency of rotor current(or emf)is the same of supply frequency