Contents
What is over-excited synchronous motor?
An over-excited synchronous motor has a leading power factor. This makes it useful for power-factor correction of industrial loads. Both transformers and induction motors draw lagging (magnetising) currents from the line.
What are types of synchronous motor?
Synchronous motors can be classified into two types based on how the rotor is magnetized….This type of synchronous motor is divided into three categories and is available in three designs, each of which has unique features:
- Hysteresis Synchronous Motors.
- Reluctance Synchronous Motors.
- Permanent Magnet Synchronous Motors.
What is normal excitation of synchronous motor?
A synchronous motor is said to have normal excitation when its Eb = V. If field excitation is such that Eb < V, the motor is said to be under-excited. In both these conditions, it has a lagging power factor as shown in Fig. 38.12.
Why do we use synchronous motors?
The advantages of the synchronous motor are the ease with which the power factor can be controlled and the constant rotational speed of the machine, irrespective of the applied load. Synchronous motors, however, are generally more expensive and a d.c. supply is a necessary feature of the rotor excitation.
Why is excitation voltage DC?
An excitation voltage or current is the amount of electric energy ( D.C ) feed into the field winding of an alternator rotor to produce magnetic flux / field. This lead to generate even more field strength and so more output voltage and so on and so on.
Which motors are 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.
How does a non excited motor work in synchronous speed?
In non-excited motors, the rotor is made of steel. At synchronous speed it rotates in step with the rotating magnetic field of the stator, so it has an almost-constant magnetic field through it. The external stator field magnetizes the rotor, inducing the magnetic poles needed to turn it.
What are the different types of synchronous motors?
There are different types of synchronous motors based on the way they are excited Let us take a look at the different types one by one. The rotor is made up of steel. The external magnetic field magnetises the rotor, and it rotates in synchronism with it. The rotor is generally made of high retentivity steel such as cobalt steel.
Do you need DC supply for synchronous motor?
The rotor locks in synchronism when the speed is near synchronous speed. They are not self-starting and need electronically controlled variable frequency stator drive. Direct current excited synchronous motors need a DC supply to the rotor to generate rotor magnetic field.
When to use salient pole rotors in synchronous motors?
Cylindrical and round rotors are used for 6 pole application. Salient pole rotors are used when a larger quantity of poles is required. Construction of the synchronous motor and synchronous alternator are similar. Working of synchronous motors depends on the interaction of the magnetic field of the stator with the magnetic field of the rotor.