Application. 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 the applications of synchronous motors?
Typical applications of these low power motors are positioning machines. They are also used in robot actuators. Synchronous motors are also used in ball mills, watches, record players, and turntables. They are also used as servo motors and timing machines.
What happens when synchronous motor is over excited?
An over-excited synchronous motor draws leading current. Therefore, if the field of the synchronous motor is overexcited then its power factor will be leading. An over-excited synchronous motor running at no load is known as the synchronous capacitor or synchronous condenser.
What is over excitation in synchronous motor?
CASE 3: If the field current is more than the normal field current, motor is said to be over excited. This excess field current produces excess flux (flux set up by DC supply rotor winding – resultant air gap flux) which must be neutralized by the armature winding. … This is called V curve of synchronous motor.
What is the application of synchronous compensators?
Explanation: The main application of the synchronous compensators is to control the reactive powers. They are designed to speeds upto 3000 rpm.
What are the benefits of synchronous motor in real world application?
Advantages | Application of Synchronous Motor
- It runs at a constant speed (synchronous speed). …
- It is not inherently self-starting.
- At no-load it draws a very small current from the mains to meet the internal losses of the motor.
Why exciter is essential for synchronous motor?
The exciter provides the power to the electromagnets that form the poles on the rotor that in turn follow the rotating magnetic field from the system.
What is the effect of increase in excitation of a synchronous motor?
From the above discussion, it is concluded that if the synchronous motor is under-excited, it has a lagging power factor. As the excitation is increased, the power factor improves till it becomes unity at normal excitation. Under such conditions, the current drawn from the supply is minimum.
How an over-excited synchronous machine improves power factor?
By varying the DC excitation of the motor, the power factor of the motor can be varied widely. Overexcited synchronous motors operate at leading power factor and provide reactive kVAR-like capacitors. This yields an improved power factor for the power-supply system.
When excitation is increased the synchronous generator operates at?
In synchronous generator, inverted V curve is drawn between field current on X-axis and power factor on Y-axis. At critical excitation the power factor is unity. If excitation is decreased, the generator operates at leading power factor and if excitation is increased, the generator operates at lagging power factor.
Why is excitation needed?
The excitation system is responsible for supplying the field current to the main rotor. The requirements of an excitation system include reliability under all conditions of service, a simplicity of control, ease of maintenance, stability and fast transient response.
What is over excitation and under excitation?
The over-excitation limiter protects the generator against over-temperature caused by high field current for long time. Under-excitation limiter prevents the decrease of generator field current to the values lower than the stability margin or the thermal limit of end side of the stator core.
What is meant by over excitation?
Overexcitation of a transformer means that the magnetic flux in the core is increased above the normal design level. … This means that the voltage must be gradually increased, with increasing frequency, in order not to overexcite the transformer.
How the synchronous motor can be used as a synchronous condenser?
A synchronous condenser is a synchronous motor running at no load and in over-excited mode. A synchronous motor in over-excited mode behaves as a capacitor which is indicated by a leading current or supply of VARs in the circuit by a synchronous motor.
What is synchronous motor?
A synchronous motor is one in which the rotor normally rotates at the same speed as the revolving field in the machine. The stator is similar to that of an induction machine consisting of a cylindrical iron frame with windings, usually three-phase, located in slots around the inner periphery.
How does a change of excitation affect its power factor?
A change in the excitation, thus, affects only the power factor of its output. … This reduces the terminal voltage slightly, so let the excitation of the first alternator be increased so as to bring the terminal voltage back to its original value.