The most widely used such a machine as a synchronous motor is in industry, where there are electric drives operating at constant speeds. For example, compressors with powerful motors, pump drives. Also, a synchronous motor is an integral part of many household appliances, for example, it is in watches.
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 poles of the inductor, created by direct current, underlies the principle of operation of such an electrical device as a synchronous motor. Typically, the inductor is located on the rotor, and the armature is located on the stator. Powerful motors use electromagnets as poles. But there is also a low-power type - a permanent magnet synchronous motor. The main difference between synchronous and asynchronous machines is the design of the stator and rotor.
For overclockingmotor up to the level of rated speed often use asynchronous mode. In this mode, the inductor winding is short-circuited. After the motor reaches rated speed, the rectifier feeds the inductor with direct current. Only at rated speed can the synchronous motor run independently.
This engine has a lot of advantages. It is an order of magnitude more complicated than an asynchronous machine, but this is offset by a number of advantages. One of the main advantages is its ability to work without the consumption or return of reactive energy. In this case, the power factor of the engine will be equal to unity. Under such conditions, the AC synchronous motor will load the network exclusively with the active component. A side effect will be a reduction in the dimensions of the motor (for an asynchronous motor, the stator winding is calculated for both active and reactive currents). However, a synchronous motor can also generate reactive power by operating in overexcited mode.
A synchronous motor is much less sensitive to surges and voltage drops in the network. Also, such electric machines have a higher resistance to overloads. By increasing the excitation currents, the overload capacity of the motor can be increased. The advantage of working with a synchronous machine is also a constant rated speed for any load (except overloads).
Undoubtedly, such a machine as a synchronous motor has its weak points. They are associated with increased costs and complex operation. The main problem is the process of excitation of the electric motor and bringing it into synchronism. At present, thyristor exciters have found distribution, which have a much higher efficiency than electric machine exciters. However, their cost is much higher. With the help of a thyristor switch, many issues can be solved: optimal regulation of excitation currents, maintaining a constant value of the cosine phi, control over the voltage on the buses, regulation of the stator and rotor currents in emergency modes and during overloads.
