What happens if field winding of the synchronous motor is short circuited? Explanation: In the case of an induction motor, the field winding is permanently short circuited by end rings. In a Synchronous motor, the rotor winding is supplied with DC excitation.
What will happen if we cut off the field circuit of the synchronous generator?
In case the field excitation of Generator is available when the steam supply to the turbine is cut off, the Synchronous Generator will draw power from the Grid and will behave as a Synchronous Motor rotating in the same direction.
What happens when excitation of synchronous motor fails?
synchronous generator. synchronous motor. … If the excitation of the generator fails, suddenly there will be no more magnetically locking between rotor and rotating magnetic field of stator.
What happens to synchronous motor if only field is excited?
If AC excitation is given then alternate North and South Pole is created on rotor field the rotor move half cycle clockwise and half cycle anti clockwise and finally stops to rotate. Thus we see that the Synchronous Motor will stop rotating.
When the field winding of an unloaded salient pole synchronous motor is open circuited the motor will?
1 Answer. If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will stop.
Why is DC excitation given?
If we rotate a wire in a constant magnetic field only then a electric current is produced. To get a constant magnetic field we have to apply a DC voltage to a coil. Only DC voltage can give a fixed magnetic field. … The rotor needs to have a constant flux and that’s why the dc excitation is provided.
What causes loss of excitation?
Generator loss of excitation (LoE) can be caused by a short circuit in the field winding, unexpected field breaker opening and by a failure in the excitation system. According to Chinese statistics, generator failure due to LoE accounts for more than 60% of all generator failures .
Why the synchronous motor is 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. … Once the rotor nears the synchronous speed, the field winding is excited, and the motor pulls into synchronization.
When should the DC excitation be applied?
When a three phase supply is connected to the stator, the synchronous motor with Damper Winding will start. It works as a three-phase induction motor. As soon as the motor approaches the synchronous speed, the DC excitation is applied to the field windings.
How do you control the speed of a synchronous motor?
Speed of synchronous motors can be controlled using two methods called open loop and close loop control. Open loop contol is the simplest scalar control method where motor speed is controlled by independent frequency control of the converter.
What are the advantages of synchronous motor?
Advantage or Merits:
One of the major advantage of using synchronous motor is the ability to control the power factor. An over excited synchronous motor can have leading power factor and can be operated in parallel to induction motors and other lagging power factor loads thereby improving the system power factor.
Does the excitation affect the synchronous motor speed?
why speed decreases as field excitation increases in synchronous machine. why the speed of the synchronous motor remains constant on any load. why with the change of excitation of a synchronous motor the magnitude of armature current first decrease and then increase.
What is excitation EMF?
The process of generating a magnetic field by means of an electric current is called excitation. Field coils yield the most flexible form of magnetic flux regulation and de-regulation, but at the expense of a flow of electric current.
Which is the case of under excitation?
Hence in this case the motor is said to operate under lagging power factor and the is said to be under excited. CASE 3: If the field current is more than the normal field current, motor is said to be over excited.
Which synchronous motor will be smallest in size?
Which synchronous motor will be smallest in size ? (D) 10 HP, 375 rpm. Explanation: Q15.
Which type of rotor is best for turbo alternator?
Smooth cylindrical type rotor is generally used for high speed alternators or turbo alternators.