Get SyncPro IIB Brush-type Synchronous Motor Field Application And Protection System

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.

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.

Rheostatic or dynamic braking A Braking of Synchronous Motor is switched on to a three-phase balanced resistive load after disconnecting it from the mains, keeping the excitation constant. To achieve greater braking torque for effective braking, the excitation may be increased.

The SPM simulates the cooling of a running motor, updating the relay thermal memory in one-minute spans. The SPM will also learn the amount of thermal capacity required for a successful motor start. Each new value of the thermal capacity is compared with the learned starting capacity required.

Circuit breakers and fuses are used as protection units for the different motors. Overcurrent protection can protect personnel from electric shock, the control equipment of the motor, the conductors of the motor branch circuits, and the motor itself from high currents.

Just like induction motors, synchronous motors must be protected against thermal excursions during starting and running as well as fault and unbalance currents that can rapidly damage the motor.

In general, overexcitation will cause the synchronous motor to operate at a leading power factor, while underexcitation will cause the motor to operate at a lagging power factor. The synchronous motor thus possesses a variable-power- factor characteristic.

Disadvantages of Synchronous Motor Synchronous motors require DC excitation at the rotor. The construction of a synchronous motor is more complicated than induction motors. Synchronous motors are costlier than induction motors.