Synchronous motor - advantages and disadvantages

The greatest distribution such machine as the synchronous engine has received in the industry where there are the electric drives working on constant speeds. For example, compressors with powerful motors, pump drives. Also, the synchronous motor is an integral part of many household appliances, for example, it is in the clock.

The principle of operation of this machine is quite simple. The interaction of the rotating magnetic field of the armature created by alternating current and the magnetic fields at the inductor poles, created by direct current, lies at the basis of the principle of operation of such an electrical device as a synchronous motor. Usually the inductor is located on the rotor, and the armature is on the stator. Powerful motors use electromagnets as poles. But there is also a low-power type - a synchronous motor with permanent magnets. The main difference between synchronous machines and asynchronous machines is the stator and rotor design.

To accelerate the engine to the nominal speed level, asynchronous mode is often used. In this mode, the inductor winding is short-circuited. After the motor reaches the rated speed, the rectifier supplies a direct current to the inductor. Only in the rated speed the synchronous motor can work independently.

This engine has a lot of advantages. It is an order of magnitude more complicated than an asynchronous machine, however this is compensated by a number of advantages. One of the main advantages is its ability to work without consumption or the return of reactive energy. At the same time, the motor power factor will be unity. Under such conditions, a synchronous AC motor will load the network with an exceptionally active component. A side effect will be a reduction in engine dimensions (for an asynchronous motor, the stator winding is calculated for both active and reactive currents). However, a synchronous motor can also generate reactive energy, working in overexcitation mode.

The synchronous motor is much less sensitive to jumps and voltage drops in the network. Also such electric machines have a higher resistance to overloads. By increasing the excitation currents, the overload capability of the motor can be increased. The plus of working with a synchronous machine is also the constant nominal speed of rotation at any load (except overloads).

Undoubtedly, such a machine as a synchronous engine has its weak points. They are associated with increased costs and complex exploitation. The main problem is the process of excitation of the electric motor and its introduction into synchronism. At the present time, thyristor pathogens are found that have a much higher efficiency than electric exciters. However, their cost is much higher. With the help of a thyristor switch it is possible to solve many problems: optimal control of excitation currents, support of a constant cosine value, control over the voltage on the bus bars, regulation of stator and rotor currents in emergency modes and during overloads.