How to quickly and easily determine whether a motor is okay or defective with a multimeter
Simply measuring the quality of the motor with a multimeter is a common method we usually use in our work. There are two main methods of measuring the quality of the motor with a multimeter: the electric block measurement and the current block measurement. Let me talk about how to use a multimeter. Simple and fast To detect whether the motor is good or not.
The most common way to use a multimeter to check is to disassemble the connecting wires between the three-phase windings before the inspection, so that the windings of the three-phase motor are not connected to each other, and then adjust the gear of the multimeter to the ohm gear of RX10K Then connect one test lead of the multimeter to one end of the winding, and connect the other test lead to the casing of the motor. At this time, we can see the resistance value indicated by the multimeter. If the resistance value indicated by the multimeter is very small or even zero at this time, it means that there is a ground fault between the phase winding of the motor and the motor casing. If the measured resistance value is very large, then there is no ground fault.
We can also use a multimeter to measure the three independent windings respectively. We first find out the normal resistance values of the three windings. If the resistance values of the three windings are the same during measurement, it means that the windings are normal. If there is a difference in the resistance of the three separate windings, the motor is not working properly. Then you can use a megger (megger) to measure the insulation resistance value between the three windings of the motor. The resistance value between them is generally between 0.5 megohm and 1 megohm, which should be a normal value. Finally, use a megger to measure the insulation of the three windings to the chassis (to the ground). The normal resistance value should be around 0.5 megohm to 1 megohm, which should be normal.
The other method is to use the multimeter to measure the current block of the multimeter, but it can only be used on small three-phase motors, such as three-phase asynchronous motors below 4KW. The rated current when it works is 8.8 amperes current. However, the current measurement value of our general multimeter is up to 10A. If you want to measure a motor with relatively large power, you can use a special clamp ammeter to measure it. We use this method mainly to measure whether the three-phase current of the motor is balanced. If the current is unbalanced, it means that the motor is also faulty.
In fact, in many cases, we can also judge the basic condition of the motor without a multimeter. For example, we can roughly judge the basic fault of the motor by "seeing", "smelling" and "touching", because when the motor fails, we are It can be seen from its operation that the speed of the motor suddenly slows down, there is abnormal noise, the surface temperature of the motor is too high, and the shell of the motor is charged, etc. are all caused by different faults in the motor.
