How to judge whether the three-phase AC motor is connected to the line and is running forward?

Generally, you can use the ohm range of 200 ohms of the multimeter to measure the resistance between the two groups of three-phase windings. If the three values ​​are basically equal, then use the range above 2000 ohms to measure the insulation of the three-phase windings to the motor casing. If the three-phase windings are well insulated to the metal casing of the motor, it can be preliminarily judged whether the coils of the motor have been damaged.

Method 1: Use a shaker to measure two of the wires. If it is a digital multimeter, the size of the test leads is too small, indicating whether the motor has been damaged.

The other two: Use the shaker to measure two of the wires, and shake the head and tail to see if there is any poor contact. If only one phase can be shaken, which two wires have the resistance value error, and the resistance value to be measured. is zero.

The shaking method is the most basic measurement tool, and there are generally analog multimeters and digital multimeters.


Under normal circumstances, the pointer multimeter of the multimeter is mechanical. If it is a high-speed multimeter, the middle finger will short the red line and the red and blue line on the handle handle of the pointer multimeter. The black line directly contacts the pressure blue, and the test pen is used to discharge.

There are also some specifications of the electric meter shaking the probe, and then loosening the connected wire, usually the red wire.
The pointer type multimeter of the electricity meter is generally a light-emitting diode type, the purpose is to increase the voltage and reduce the current, so as to avoid damage due to excessive voltage. Measured with an overcurrent meter, the larger the current, the smaller the current, and vice versa, the larger the value, the smaller the value.

The pointer multimeter of the electric meter has an important name called "", which means that it represents the two sides of the coil, one is the main and secondary coils, and the other is the secondary side.