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How does an auxiliary winding provide a starting torque for single-phase induction motors?
Single- and three-phase motors work on the sameprinciple. The field windings create a rotating field which cuts the rotor bars of the rotor, inducing voltages into them, and the field produced by the resulting currents react with the rotating field causing the rotor to spin. If you like, the rotating field 'drags' the rotor around with it.In the case of a three-phase motor, the three out-of-phase phase currents create a naturally-rotating field. However, in the case of a single-phase motor, we must simulate this. This is done by having two, separate, field windings. One is fed directly from the supply, and the other is also fed from the supply via a capacitor. This results in two field currents which are displaced from each other by around 90 electrical degrees, when then create the rotating field necessary for the motor to start and run. You could say that a single-phase motor is equivalent to a 'two-phase' motor. The field winding supplied via a capacitor is known as the 'start winding' or the 'auxiliary winding'.
Why squirrel cage motor is NOT suitable for use as a DC machine?
A 'squirrel cage' rotor is used in an a.c. inductionmotor, meaning that there is no electrical supply to that rotor with the currents in the rotor , instead, being the result of induced voltages caused by currents flowing in the field windings. A rotor of a d.c. motor, is electrically connected to the supply. The two types of motor work on completely different principles, so cannot use a squirrel cage rotor.
Why is the starting torque of a wound -rotor motor higher per ampere of starting current than that of a squirrel cage motor?
The starting torque of a wound-rotor motor is higher per ampere of starting current than that of a squirrel cage motor due to the ability to control the rotor resistance. In a wound-rotor motor, external resistance can be added to the rotor circuit, allowing for increased torque production during startup without drawing excessive current. In contrast, squirrel cage motors have a fixed rotor resistance, which limits their starting torque and results in a relatively lower torque per ampere of starting current. This design feature enables wound-rotor motors to provide better performance in high-torque applications.
How does the centrifugal switch work in a single phase electric motor?
In a single phase electric motor, the centrifugal switch allows the start winding to be energized through the start capacitor when the motor is starting. This gives an out of phase magnetic field that, along with the in phase magnetic field from the run winding, helps the rotor to begin spinning. Once the rotor reaches a certain speed, the centrifugal switch changes state and cuts off the start winding. At that point, the motor continues running only through its run winding, and inertia keeps the rotor properly phase biased relative to the run winding's magnetic field.
What is the use of double cage rotor in induction motor?
to obtain high starting torque
Explain starting of a wound rotor induction motor?
explain wound rotor
How does an auxiliary winding provide a starting torque for single-phase induction motors?
Single- and three-phase motors work on the sameprinciple. The field windings create a rotating field which cuts the rotor bars of the rotor, inducing voltages into them, and the field produced by the resulting currents react with the rotating field causing the rotor to spin. If you like, the rotating field 'drags' the rotor around with it.In the case of a three-phase motor, the three out-of-phase phase currents create a naturally-rotating field. However, in the case of a single-phase motor, we must simulate this. This is done by having two, separate, field windings. One is fed directly from the supply, and the other is also fed from the supply via a capacitor. This results in two field currents which are displaced from each other by around 90 electrical degrees, when then create the rotating field necessary for the motor to start and run. You could say that a single-phase motor is equivalent to a 'two-phase' motor. The field winding supplied via a capacitor is known as the 'start winding' or the 'auxiliary winding'.
Why squirrel cage motor is NOT suitable for use as a DC machine?
A 'squirrel cage' rotor is used in an a.c. inductionmotor, meaning that there is no electrical supply to that rotor with the currents in the rotor , instead, being the result of induced voltages caused by currents flowing in the field windings. A rotor of a d.c. motor, is electrically connected to the supply. The two types of motor work on completely different principles, so cannot use a squirrel cage rotor.
What happens if 3 phase supply is given to stator and rotor both in a induction motor?
its impossible to give suppy to rotor of an induction motor,because of it a closed path for circulating currents.
Why does the rotor of an induction motor turn slower than the revolving field?
In an induction motor the rotor currents are induced by the magnetic field of the stator, and if the motor were to run at synchronous speed the induced currents and also the torque would fall to zero. The rotor currents alternate at a low frequency determined by the 'slip', which is the percentage amount that the rotor speed is below the synchronous speed. The output torque is proportional to the slip at near-synchronous speeds.
Why is the starting torque of a wound -rotor motor higher per ampere of starting current than that of a squirrel cage motor?
The starting torque of a wound-rotor motor is higher per ampere of starting current than that of a squirrel cage motor due to the ability to control the rotor resistance. In a wound-rotor motor, external resistance can be added to the rotor circuit, allowing for increased torque production during startup without drawing excessive current. In contrast, squirrel cage motors have a fixed rotor resistance, which limits their starting torque and results in a relatively lower torque per ampere of starting current. This design feature enables wound-rotor motors to provide better performance in high-torque applications.
How does the centrifugal switch work in a single phase electric motor?
In a single phase electric motor, the centrifugal switch allows the start winding to be energized through the start capacitor when the motor is starting. This gives an out of phase magnetic field that, along with the in phase magnetic field from the run winding, helps the rotor to begin spinning. Once the rotor reaches a certain speed, the centrifugal switch changes state and cuts off the start winding. At that point, the motor continues running only through its run winding, and inertia keeps the rotor properly phase biased relative to the run winding's magnetic field.
Why a single phase motor is not self starting?
For a rotating part need two equal & opposite forces separated by a some distant acting on its edges of axis are needed. In a single phase motor the winding produces a single force on the rotor. In order to achieve a force couple on rotor two windings fed from a single phase source are split in to two forces with the help of a capacitor. With such an arrangement two rotating forces which are 90 electrical degrees apart are produced. Thus forming a force couple on the rotor.
Is it necessary to have three phase rotor windings for the transmitter and motor in selsyn motor?
No, it is not necessary to have three-phase rotor windings for a transmitter and motor in a selsyn motor. Selsyn motors typically use single-phase rotor windings to transfer information or control signals between devices. The synchronization between the transmitter and motor is achieved through the interaction of the stator and rotor windings.
How is direction of rotation for single phase induction motor determined?
A single phase induction motor is not self starting; thus, it is necessary to provide a starting circuit and associated start windings to give the initial rotation in a single phase induction motor. The normal running windings within such a motor can cause the rotor to turn in either direction, so the starting circuit determines the operating direction.
What is the use of double cage rotor in induction motor?
to obtain high starting torque
How starting torque of an induction motor can be increased?
For a single phase motor, this can be done by connecting a capacitor in series with the starting windings. For three phase motors, this can be done by connecting starting resistors in the stator windings at starting. This reduces the stator current and hence it's flux density. Thus the rotor will have less opposition starting to rotate. Hence, the torque has increased.
