Introduction to motor rotor

The rotor is mainly divided into three parts, the rotating shaft, the rotor core and the rotor conductor. The stator bearing supports the rotating shaft, and the rotating shaft transmits mechanical energy to the load. The rotor core is made of silicon steel sheets to reduce eddy current losses. The rotor conductor is divided into squirrel cages. type and winding type. The advantage of the wound rotor is that it has higher starting torque. After the advent of frequency converters, most systems that use slip rings to control speed have been replaced by squirrel-cage motor systems driven by frequency converters. Squirrel cage rotors are divided into aluminum rotors or copper rotors. The resistance coefficient of copper is 1.7×10⁻⁸, which is lower than the resistance coefficient of aluminum 2.82×10⁻⁸. Under the same volume, the resistance value of copper is lower than that of aluminum.

When the primary side stator coil is energized, a rotating magnetic field is generated. The magnetic field cuts the conductor on the rotor, generates an induced electric potential and induces a current. Under the action of the current and the magnetic field, the rotor generates torque.

There is an air gap between the stator and the rotor, which will produce higher impedance for the magnetic circuit. A smaller air gap can have lower noise and better efficiency, while a larger air gap can have better stability for high-power motors. Spend. When the mass distribution of the rotating body is uneven and the rotating body is unbalanced, the rotation is prone to vibration and noise. In order to avoid this situation, a dynamic balance correction test will be performed.

The aluminum rotor:

The aluminum rotor can be flexibly designed into the best shape, and the rotor's fan blades, squirrel cage rotor strips and end rings can also be cast at the same time to improve heat dissipation efficiency. The structure of the cast aluminum rotor is symmetrical and compact, making it easy to achieve mechanical balance. The melting point of pure aluminum is 660°C, which is much lower than the melting point of pure copper of 1083°C. In terms of manufacturing, it can reduce the production cycle and the price is low, so it is widely used. And the mass of aluminum of the same volume is only less than one-third of copper, so it can be turned to a higher speed.。

The copper rotor:

Under the same size, the resistance of the copper rotor is only about 60% of that of the aluminum rotor, so it is easy to have higher efficiency and larger output power. In application, it can reduce power consumption and reduce operating costs. Copper is also corrosion-resistant, and cast copper rotors are suitable for use in brine pumps, hot water circulation pumps, etc.