Electrical motor in general is an electro-mechanical device that converts energy from electrical domain to mechanical domain. Based on th...

Electrical motor in general is an electro-mechanical device that converts energy from electrical domain to mechanical domain. Based on the type of input we have classified it into single phase and 3 phase motors. Among 3 phase motors, induction motors and synchronous motors are more widely used. When a 3 phase electric conductors are placed in a certain geometrical positions (In certain angle from one another) then an electrical field is generated. Now the rotating magnetic field rotates at a certain speed, that speed is called synchronous speed. Now if an electromagnet is present in this rotating magnetic field, the electromagnet is magnetically locked with this rotating magnetic field and rotates with same speed of rotating field.
Synchronous motors is called so because the speed of the rotor of this motor is same as the rotating magnetic field. It is basically a fixed speed motor because it has only one speed, which is synchronous speed and therefore no intermediate speed is there or in other words it’s in synchronism with the supply frequency. Synchronous speed is given by

where f = supply frequency & p = no. of poles

## Construction of Synchronous Motor

Normally it's construction is almost similar to that of a 3 phase induction motor, except the fact that the rotor is given DC supply, the reason of which is explained later. Now, let us first go through the basic construction of this type of motor.
From the above picture, it is clear that how this type of motors are designed. The stator is given is given three phase supply and the rotor is given dc supply.

## Principle of Operation Synchronous Motor

Synchronous motor is a doubly excited machine i.e two electrical inputs are provided to it. It’s stator winding which consists of a 3 phase winding is provided with 3 phase supply and rotor is provided with DC supply. The 3 phase stator winding carrying 3 phase currents produces 3 phase rotating magnetic flux. The rotor carrying DC supply also produces a constant flux. Considering the frequency to be 50 Hz, from the above relation we can see that the 3 phase rotating flux rotates about 3000 revolution in 1 min or 50 revolutions in 1 sec. At a particular instant rotor and stator poles might be of same polarity (N-N or S-S) causing repulsive force on rotor and the very next second it will be N-S causing attractive force. But due to inertia of the rotor, it is unable to rotate in any direction due to attractive or repulsive force and remain in standstill condition. Hence it is not self starting.
To overcome this inertia, rotor is initially fed some mechanical input which rotates it in same direction as magnetic field to a speed very close to synchronous speed. After some time magnetic locking occurs and the synchronous motor rotates in synchronism with the frequency.

### 2.Synchronous motor finds application where operating speed is less (around 500 rpm) and high power is required. For power requirement from 35 kW to 2500 KW, the size, weight and cost of the corresponding three phase induction motor is very high. Hence these motors are preferably used. Ex- Reciprocating pump, compressor, rolling mills etc.

Name

BASIC ELECTRICAL,12,BATTERIES,4,CIRCUIT THEORIES,9,CONTROL SYSTEMS,3,DC MOTOR,1,DIGITAL ELECTRONICS,1,DISTRIBUTED GENERATION,2,DISTRIBUTION,6,ELECTRICAL DRIVES,1,ELECTRICAL LAWS,8,ELECTRONICS DEVICES,2,General,7,GENERATION,3,GENERATOR,1,HIGH VOLTAGE,4,ILLUMINATION,1,INDUCTION MOTOR,7,MATERIALS,1,MEASUREMENT,1,MOTOR,1,POWER ELECTRONICS,2,PROJECTS ON INDUCTION MOTOR,1,PROTECTION,1,SMART GRID,3,SWITCHGEAR,4,SYNCHRONOUS MOTOR,1,TRANSFORMER,6,TRANSMISSION,4,
ltr
item
Electrical for Us: Synchronous Motor Working Principle
Synchronous Motor Working Principle
http://www.electrical4u.com/equations/synchronous-speed.gif
Electrical for Us
http://www.sanjaysah.com.np/2016/11/synchronous-motor-working-principle.html
http://www.sanjaysah.com.np/
http://www.sanjaysah.com.np/
http://www.sanjaysah.com.np/2016/11/synchronous-motor-working-principle.html
true
3851448774078769448
UTF-8