How Synchronous Motor Works

November 17, 2024 Post a Comment

How synchronous motor works

At present, damper windings are most widely used method of starting a synchronous motor. A damper winding is made up of heavy copper bars inserted in slots cut into the pole faces of the rotor as shown in Figure-2. These copper bars are then short-circuited by end rings at both ends of the rotor.

How does a synchronous motor rotate?

The north and south poles of the rotor and the stator interlock each other. Thus, the rotor starts rotating at the speed of the rotating magnetic field. And the motor runs at a synchronous speed. The speed of the motor can only be changed by changing the frequency of the supply.

What is a synchronous motor used for?

Synchronous motors are normally used in applications in which a constant and precise speed is required. 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.

How synchronous motor works as a power factor?

Unity power factor synchronous motors are designed to operate in this way. A full load, with excitation they require no lagging reactive kVA from the line, nor do they supply leading reactive kVA to the line; they run at unity power factor with a minimum amount of stator current, and hence at highest efficiency [15].

Why synchronous 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 do you control the speed of a synchronous motor?

We can achieve the speed control of synchronous motor either by changing the number of Stator poles or changing the frequency of AC supply. Varying the frequency is a feasible way for speed control of the synchronous motor. Using the rectifier and inverter combination, we can vary the frequency of AC supply.

Why synchronous motor is doubly excited?

Detailed Solution. A synchronous machine is called a doubly excited machine because both its rotor and stator are excited. To achieve magnetic locking between stator and rotor, double excitation needed. The stator of 3 phase synchronous motor is excited with a 3-phase supply while rotor is with DC Supply.

Why DC supply is used in synchronous motor?

In a synchronous motor, AC power is supplied to the stator to generate a rotating magnetic field. DC power is supplied to the rotor which results in discrete North (N) and South (S) poles. The poles in the rotor then lock onto (synchronize) and follow the opposing rotating magnetic pole (N follows S).

What is field current in synchronous motor?

In a synchronous motor, a 3-phase set of stator currents produces a rotating magnetic field causing the rotor magnetic field to align with it. The rotor magnetic field is produced by a DC current applied to the rotor winding.

Are asynchronous motors AC or DC?

An induction motor or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding.

Is a synchronous motor a DC motor?

A synchronous motor is one in which the rotor turns at the same speed as the rotating magnetic field in the stator. Step motors, dc brushless, variable reluctance motors, switched reluctance and hysteresis motors, and dc brush motors all typically operate as synchronous motors.

Can synchronous motor work on DC?

The only major current-excited synchronous motor available is the direct current-excited synchronous motor, which requires a DC input as well as an AC input.

Why is synchronous speed constant?

The constant speed characteristic is achieved by interaction between a constant and rotating magnetic field. Rotor of synchronous motor produces a constant magnetic field and Stator produces a Rotating magnetic field.

What is exciter in synchronous motor?

Excitation System in Small-size Synchronous Machines For small size synchronous machines (motor or generator), the direct current is supplied to the rotor field winding by a DC generator, known as exciter. The exciter is mounted on the shaft of the synchronous machine.

Why there is no slip in synchronous motor?

To prevent this slip, synchronous rotors have field coils with a stationary magnetic pole on each of the subsequent poles determined by the design/speed in which it was manufactured. This setup causes each magnetic pole on the rotor to stay “in sync” with the rotational magnetic field produced by the stator windings.

What are the advantages of synchronous motor?

Advantages of Synchronous Motor It operates at a constant speed (i.e., synchronous speed) from no-load to full-load. Power factor of a synchronous motor can be easily controlled by changing the excitation of the motor. For low speed (< 300 RPM) applications, synchronous motors are more economical than induction motors.

What is a 3-phase synchronous motor?

A 3-phase synchronous motor is a 3-phase synchronous machine which is operated as a motor i.e. converts electrical energy input into mechanical energy output.

What is synchronous speed formula?

The synchronous speed of an AC motor is determined by the frequency of the source and the number of poles. The RPM is calculated by multiplying the frequency times 60 and dividing by the number of pairs of poles.

How does synchronous motor change rpm?

We can control the speed of the synchronous motor by changing the frequency of the supply to the motor.

Why are synchronous motors more efficient?

Synchronous motors generally have a higher power density than induction motors of comparable size, allowing them to provide more power at a smaller volume. This is great for size-constrained applications and is a reason to choose a synchronous motor over an induction motor.