What happens when one phase of synchronous motor is short circuited?
An open circuit in one phase of the motor itself or a short circuit will prevent the motor from starting.
When synchronous motor is started the field winding is?
While starting a synchronous motor, the field winding must be shorted through a suitable resistance so that the induced voltage is distributed throughout the whole winding and no part is subjected to the high voltage induced in the entire winding.
Why the field circuit of the synchronous motor need to be shorted at the time of starting?
The damper winding is shorted by shorting the slip rings. The initial resistance added in the rotor not only provides high starting torque but also limits high inrush of starting current. Hence it acts as a rotor resistance starter.
What happens when motor is short circuited?
A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit.
Why synchronous motors are generally not self starting?
Above a certain size, synchronous motors are not self-starting motors. This property is due to the inertia of the rotor; it cannot instantly follow the rotation of the magnetic field of the stator. … Because of this action, the rotor will be subjected to an instantaneous torque in an anticlockwise direction.
What is the synchronous speed of an AC motor?
The synchronous speed is the speed of the revolution of the magnetic field in the stator winding of the motor. It is the speed at which the electromotive force is produced by the alternating machine.
What does the power factor of an alternator depend on?
Power factor of the alternator defines the phase angle between the current drawn and applied voltage. The power factor of the alternator depends upon the type of load. In case if it is an infinite bus, then the power factor of the alternator depends upon the excitation of the alternator.
Why the speed of synchronous motor is constant?
Synchronous motors are constant speed motors. They run at the synchronous speed of the supply. … As you can see, the synchronous speed depends on the frequency of the supply and the number of poles of the rotor. Changing the number of poles is not easy, so we do not use that method.
How does a 3 φ synchronous motor start?
A three-phase synchronous motor has no starting torque. … Once up to speed, the rotor field can be excited with direct current and the rotor is, in effect, then dragged around at the same speed as the three-phase stator field. Its speed is synchronized with that of the stator field.
Which type of starter is used for synchronous motor?
Controllers for synchronous motors have four components: a three-pole starter for the ac stator circuit, a contactor for the dc field circuit, an automatic synchronizing device to control the dc field contactor, and a cage-winding protective relay to open the ac circuit if the motor operates too long without …