The synchronous motor

Since the motor cannot produce synchronous torque if it falls out of synchronization, practical synchronous motors have a partial or complete squirrel-cage damper amortisseur winding to stabilize operation and facilitate starting.

Induction motors do not require any additional power source. This causes a demagnetizing effect due to armature reaction. Once the rotor locks in with the rotating magnetic field, the motor is said to be The synchronous motor synchronization.

An asynchronous motor is popularly called as Induction motor. With increasing field current armature current at first decreases, then reaches a minimum, then increases.

Induction The synchronous motor always runs at a speed which is less than the synchronous speed. Both the types are quite different from each other. No starting mechanism is required in induction motors. Synchronous motors are costlier.

Ex- Reciprocating pump, compressor, rolling mills etc. We apply three phase supply to the stator and DC supply to the rotor. Because this winding is smaller than that of an equivalent induction motor and can overheat on long operation, and because large slip-frequency voltages are induced in the rotor excitation winding, synchronous motor protection devices sense this condition and interrupt the power supply out of step protection.

In some machines or when a large number of poles are needed, a salient pole rotor is used. Synchronous motors are mechanically coupled with another motor.

Synchronous Motor Working Principle

Synchronous motor finds application where operating speed is less around rpm and high power is required. Generally a salient pole rotor is used on which rotor winding is mounted. Its stator winding, which consists of a 3 phase winding, is provided with a 3 phase supply, and the rotor is provided with a DC supply.

At a particular instant rotor and stator poles might be of the same polarity N-N or S-S causing a repulsive force on the rotor and the very next instant it will be N-S causing attractive force.

Synchronous motors are generally more efficient than induction motors. On achieving synchronous speed, magnetic locking occurs, and the synchronous motor continues to rotate even after removal of external mechanical means. Synchronous motor Induction motor: Considering the 50 Hz power frequency, from the above relation we can see that the 3 phase rotating flux rotates about revolutions in 1 min or 50 revolutions in 1 sec.

A single-phase or two-phase derived from single phase stator winding is possible, but in this case the direction of rotation is not defined and the machine may start in either direction unless prevented from doing so by the starting arrangements.

The power factor of a synchronous motor can be adjusted to lagging, unity or leading by varying the excitation, whereas, an induction motor always runs at lagging power factor.

Synchronous Motor

The minimum point is also the point at which power factor is unity. It could be either 3 phase induction motor or DC shunt motor. Very large motor systems may include a "pony" motor that accelerates the unloaded synchronous machine before load is applied.

Synchronous motor always runs at a speed equal to its synchronous speed. Here, we do not apply DC excitation initially. This makes it being used in electrical power factor improvement. Excitation at which the power factor is unity is termed normal excitation voltage. A rotor with permanent magnets can also be used.

After some time when magnetic locking takes place supply to the external motor is cut off. It rotates at speed very close to its synchronous speed, and then we give the DC excitation.

Difference between Synchronous motor and Induction motor

Major differences between a synchronous motor and an induction motor are discussed below. Synchronous condenser V-curve of a synchronous machine By varying the excitation of a synchronous motor, it can be made to operate at lagging, leading and unity power factor. For power requirement from 35 kW to KW, the size, weight and cost of the corresponding three phase induction motor is very high.

Here we use some mechanical means which initially rotates the rotor in the same direction as the magnetic field to speed very close to synchronous speed.Synchronous Motor Working Principle Posted by Sibasish Ghosh on 22/7/ & Updated on 19/8/ Electrical motor in general is an electro-mechanical device that converts energy from electrical domain to mechanical domain/5(22).

A synchronous electric motor is an AC motor in which, at steady state, the rotation of the shaft is synchronized with the frequency of the supply current; the rotation period is exactly equal to an integral number of AC cycles. Synchronous motors contain multiphase AC electromagnets on the stator of the motor that create a magnetic field which rotates.

Induction motor: Stator winding is similar to that of a synchronous mint-body.com is wound for a specific number of poles. A squirrel cage rotor or a wound rotor can be used. In squirrel cage rotor, the rotor bars are permanently short-circuited with end rings.

The self-excited synchronous motor, also called a switched-reluctance motor, contains a rotor cast of steel that includes notches or teeth.

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The synchronous motor
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