The clearest collection of motor principles in history
Electric motor (commonly known as "motor") refers to an electromagnetic device that converts or transmits electrical energy based on the law of electromagnetic induction. Its main function is to generate driving torque as a power source for electrical appliances or various machinery.

An electric motor mainly consists of an electromagnet winding or distributed stator winding used to generate a magnetic field, a rotating armature or rotor, and other accessories. Under the action of the rotating magnetic field in the stator winding, there is current passing through the armature squirrel cage aluminum frame and it is rotated by the magnetic field.

Stator (stationary part)

Stator core: a part of the motor magnetic circuit, on which the stator winding is placed;

Stator winding: It is the circuit part of an electric motor that is supplied with three-phase AC power to generate a rotating magnetic field;

Machine base: Fix the stator iron core and front and rear end caps to support the rotor and provide protection, heat dissipation, and other functions;

Rotor (rotating part)

Rotor iron core: as a part of the motor magnetic circuit and placing rotor windings in the iron core slot;

Rotor winding: Cutting the rotating magnetic field of the stator generates induced electromotive force and current, and forms electromagnetic torque to rotate the motor;

The difference between repairing variable frequency motors and ordinary motors

1、 Select electromagnetic wires with good corona resistance to meet the requirements of the motor's resistance to high-frequency pulses and partial discharges.

Generally, polyester imide/polyamide imide composite layer enameled wire is used, which is resistant to corona and corona electromagnetic wire.

2、 Construction techniques for winding and embedding wires.

The processing technology of variable frequency motors, such as winding, embedding, and binding, must be strictly managed, especially to prevent damage to the wires during the winding and embedding process. The embedding process should ensure that the slot insulation, phase insulation, and interlayer insulation are placed in place. The phase insulation should be made of materials that are easily soaked by insulation paint, and the coil ends should be reinforced and fixed to ensure that the ends become a whole.

Strengthening insulation at the bottom of the motor slot, between phases, between layers, and at the beginning and end turns of the coil can improve the electrical strength of the motor.

3、 The main insulation must use air gap free insulation.

The air gap in the insulation structure of variable frequency motors is the main factor causing corona. In order to ensure that there is no air gap in the overall insulation structure of the motor, according to the national standard GB/T51707-2008 "Insulation Specification for Three phase Asynchronous Motors for Variable Frequency Speed Control", the impregnating paint used for three-phase asynchronous motors for variable frequency speed control must be no less than Class F solvent-free paint, with a volatile content of less than 10%, and adopt VPI process. This process also aims to improve the overall mechanical strength of the insulation structure.

4、 Match the frequency converter, cable, and motor properly, and limit the length of the cable between the motor and the power supply.

Due to the impedance mismatch of the power line, as the length of the cable between the frequency converter and the motor increases, the amplitude of the overvoltage at the motor end also increases, which can easily cause partial discharge. Therefore, according to the specific characteristics and actual needs of the variable frequency power supply, the length of its connecting cable should be shortened as much as possible to reduce the amplitude of overvoltage and local discharge at the motor end, and extend the service life of the motor.

The power cord of variable frequency motors generally uses professional cables, also known as symmetrical conductor variable frequency cables, which are 3P+3N/E series, that is, the original 3+1 is divided into 3 pieces.