Abstract: This article delves into the starting methods of Permanent Magnet Synchronous Motors (PMSMs). It discusses various techniques used to initiate and maintain operation, highlighting the unique characteristics of PMSMs and how these differences from traditional induction motors impact the starting process.

Introduction to Permanent Magnet Synchronous Motors (PMSMs)

Permanent Magnet Synchronous Motors (PMSMs), with their rotor fields comprising permanent magnets, offer several advantages over induction motors. The absence of brushes and commutator simplifies their construction and enhances reliability. However, this simplification introduces a unique challenge: how to start the motor without the traditional means of mechanical commutation.

Starting Methods for PMSMs

Induction Motor Starting

In the absence of a commutator, PMSMs require a different approach to start operation. One method involves damper windings on the rotor, where the motor is initially operated as an induction motor without the field winding supply. As the motor reaches full speed, the field winding provides the necessary magnetic field, enabling synchronous operation. Another technique includes the use of a start motor, a smaller motor that aids in the initial starting process.

Using Hall Sensors for Rotor Position Detection

For precise timing of stator current switching, Hall sensors are commonly used to detect the position of the rotor. These sensors provide real-time positional information, allowing the motor controller to make accurate switches at the right moments, ensuring smooth and efficient operation.

Use of Pilot Windings and Centrifugal Switches

Another starting technique involves the use of a second winding (pilot coil) that is activated by a centrifugal switch. As the motor accelerates, the pilot coil helps to bring the main winding into operation. This method minimizes the current drawn during the transition, ensuring reduced operational load and smoother performance.

Resistor and Contactor Start Methods

Many PMSMs are started using contactor or switch-based methods. A contactor automatically connects the field winding as the speed increases, while a starter switch manually performs this task. The application and motor type often dictate the choice of starting method.

Self-Starter Mechanism and Squirrel Cage Windings

While conventional synchronous motors cannot self-start, PMSMs employ a unique self-starting mechanism. Short-circuited damper windings on the rotor behave similarly to squirrel cage windings, initiating the starting process. Once the motor achieves sufficient speed, the poles engage, becoming magnetically locked to the synchronous speed of the stator field.

Hybrid Motor Applications

Some motors, by combining features of both synchronous and stepper motors, achieve enhanced control and functionality. Pole Positioning and the addition of a "hold" position enable these hybrid motors to perform precise movements. The starting process in such motors involves seeking a specific pole position, which requires a higher current pulse to overcome the locked rotor inertia and charge the relevant coils.

Conclusion and Future Trends

The unique characteristics of PMSMs necessitate specialized starting methods. Hall sensors, damper windings, and other technologies play crucial roles in facilitating smooth operation. As technology advances, hybrid motors that integrate multiple motor types will continue to evolve, meeting the demands of modern appliances and industrial applications.