1. megohmmeter: It can be used to measure the insulation resistance between each phase of the motor and the ground, and its value should not be less than 0.5 megohmmeter.

2. Multimeter: used to check the on-off measurement of motor coil.

3. Single-arm bridge: accurately measure the coil resistance, and you can know whether the coil resistance of each phase is close, especially after rewinding, there are two major mechanical and electrical faults. ?

Extended data:

According to the working power supply:

According to the different power sources of motors, they can be divided into DC motors and AC motors. Among them, AC motors are divided into single-phase motors and three-phase motors.

According to the structure and working principle:

According to the different structure and working principle of motor, it can be divided into DC motor, asynchronous motor and synchronous motor.

Synchronous motors can also be divided into permanent magnet synchronous motors, reluctance synchronous motors and hysteresis synchronous motors.

Asynchronous motors can be divided into induction motors and AC commutator motors. Induction motors are divided into three-phase asynchronous motors, single-phase asynchronous motors and shielded pole asynchronous motors. AC commutator motor is divided into single-phase series motor, AC -DC dual-purpose motor and repulsion motor.

According to the structure and working principle, DC motors can be divided into brushless DC motors and brushed DC motors. Brushed DC motors can be divided into permanent magnet DC motors and electromagnetic DC motors.

Electromagnetic DC motors can be divided into series DC motors, parallel DC motors, separately excited DC motors and composite DC motors. Permanent magnet DC motors are divided into rare earth permanent magnet DC motors, ferrite permanent magnet DC motors and Al-Ni-Co permanent magnet DC motors.

When the three-phase stator winding of the motor is energized with three-phase symmetrical alternating current, it will generate a rotating magnetic field, which will cut the rotor winding, thus generating an induced current in the rotor winding (the rotor winding is a closed path), and the current-carrying rotor conductor will generate electromagnetic force under the action of the stator rotating magnetic field, thus forming electromagnetic torque on the motor rotating shaft and driving the motor to rotate.

When a conductor cuts magnetic lines in a magnetic field, an induced current is generated in the conductor, hence the name "induction motor". The combined action of induced current and magnetic field exerts driving force on the motor rotor.

We let the closed coil ABCD rotate around the xy axis in the magnetic field B. If the magnetic field is rotated clockwise, the closed coil will be subjected to variable magnetic flux, which will produce induced electromotive force and induced current (Faraday's law).

According to Lenz's law, the direction of current is the reason why the action of induced current always hinders induced current. Therefore, each conductor bears the Lorentz force F which is opposite to the motion direction of the induced magnetic field.

A simple way to determine the force F direction of each conductor is to use the right-hand three-designation rule (the magnetic field acts on the current to place the thumb in the direction of the induced magnetic field and the index finger in the direction of the force).

Place the middle finger in the direction of the induced current. In this way, the closed coil bears a certain torque and rotates in the same direction as the magnetic field of the inductor, which is called rotating magnetic field. The electric torque generated by the rotation of the closed coil balances the load torque.