Asynchronous motor: construction and device

Three-phase asynchronous motor withThe squirrel-cage rotor was invented back in 1889, on March 8, by the famous Russian scientist and engineer Mikhail Osipovich Dolivo-Dobrovolsky. And literally a year later, on December 15, 1890, a phase-rotor motor was invented and patented.

Three-phase asynchronous electric motor - one ofThe most common electrical apparatus in the industry. It is easy to operate, reliable and has a rather low price. An asynchronous electric motor actually takes up ninety percent of the total number of engines around the world. It can be found almost everywhere - from the construction of a conventional washing machine, to huge industrial workshops, not to mention power plants. He made a significant technical revolution in the global industry.

An asynchronous motor is a machinewhich is designed to convert electrical energy into mechanical energy. "Asynchronous" simply means "not simultaneous." This means that for such a machine the frequency with which the magnetic field generated by the stator rotates will always be greater than the frequency with which the moving part of the engine rotates.

An asynchronous electric motor consists of a fixed part - the stator, and a movable rotating part - the rotor.

The stator is assembled from sheets of compressedelectrical steel and usually has the shape of a cylinder. A stator winding made of a magnet wire is laid in special grooves of the core. There are several windings at the stator. The axes of these windings are usually shifted by an angle of 120 degrees relative to each other. The ends of these windings can be connected by a star or a triangle (depending on the voltage applied).

The rotors of such a machine as an asynchronous electric motor, are short-circuited and phase.

The first type (squirrel-cage rotor) iscore, which is assembled from copper or aluminum rods with winding laid in them. The rods are connected by end rings, and their appearance resembles a squirrel cage. By the way, that is why this type of rotor is often called “squirrel cage”. In this case, the rotor is again assembled from electrical steel sheets, pressed and cast in aluminum.

Phase rotor is often called a rotor withslip rings. It has a three-phase winding, which is virtually no different from the stator windings. Basically, the ends of the windings of such a rotor with contact rings (phase) are connected into a star. The free ends are brought to these most contact rings. An additional resistor is often added to the winding circuit due to the presence of special brushes connected to the rings. Such a resistor increases the resistance in the rotor electric circuit, which contributes to a smoother start-up and a decrease in starting current values ​​- this is very important for such machines as three-phase asynchronous electric motors.