How to test the quality of the motor with a multimeter
1. The motor is short-circuited to the ground. The test method is to use a shaking meter to ground one end and connect the other end to the motor terminal. The insulation is zero when shaken.
2. The open circuit between turns of the motor. The test method is to connect the two ends of the shaker to the two terminals of the motor, and the insulation is greater than zero when measured by shaker.
3. Short circuit between turns of the motor, test with a bridge.
Multimeter measurement:
1. The phase-to-phase resistance is uniform, don’t worry about how much the resistance is, just be uniform. For motors larger than 15kw, you may measure 0 ohms no matter what, that’s because the range of the multimeter is too large. Change to a micro-ohmmeter.
2. The insulation of the phase line to the motor shell is greater than 1m ohms. How to judge the quality of the three-phase asynchronous motor? When measuring the single-phase motor, the capacitor should be disconnected. 1. Measure the current, and the three-phase unbalance rate is not more than 10%; Surface insulation, each phase-to-ground, phase-to-phase are not less than 0.5 trillion;
3. The DC resistance is measured by the bridge, and the three-phase unbalance rate is not more than 2%;
In addition to the method mentioned above, the way to check whether the winding is normal is to connect the small current range of the multimeter (such as 50 microamps) to any two of the leads. At this time, use the motor to rotate, and the needle of the multimeter should be clearly Swing (related to the speed of rotation). This is the "soil" method of using the residual magnetism of the motor to check the windings. If the winding is burned, the watch hands will definitely not move. A multimeter can be used to judge the phase-to-phase short circuit, grounding and open circuit of the motor, but it is not easy to judge the inter-turn short circuit.
Measuring only with a multimeter is not very accurate. It is best to use a megohmmeter to measure the insulation resistance of each phase, and then use a DC bridge to measure the DC resistance between the three-phase windings. Whether it is balanced and whether the value is too large or too small is absolutely accurate. The three-phase winding resistance should be equal, and the phase-to-phase and phase-to-housing insulation resistance should be greater than 1 megohm. The overloaded windings are burned, and the phase is missing, the two groups are burned and the other group is not burned.
How to use a multimeter to identify a single-phase motor? Generally, the DC resistance of the starting winding of a single-phase motor is greater than that of the running winding. The simplest method of identification is:
1. First use a multimeter to measure the DC resistance from the common terminal to the running winding terminal and the starting winding terminal respectively
2. Then use a multimeter to measure the DC resistance from the running winding end to the starting winding end.
3. If the arithmetic sum of the two measurements in "1" is not equal to the measured value in "2", then the motor must be burned! If they are equal, it is best to compare with the same type of motor, or find the factory parameters of the motor Compare. To judge the quality of the motor.
When measuring a single-phase motor, the capacitor should be disconnected. For a single-phase motor short circuit, you have to have a normal resistance value as a reference.
How to use a multimeter to judge whether the motor of the electric fan is burnt out? The method is as follows:
The motor of the electric fan has 5 wires. They are: 1st gear, 2nd gear, 3rd gear, and 2 capacitor wires. Generally speaking, except for some motors, the wire colors of the 3 gears are red, blue, and green. The capacitors are black and yellow. Then start, take out the 5 wires of the motor. First, you adjust the gear of the multimeter to the ohm gear, connect the red test lead to any capacitor line, and connect the black test lead to Level 1. You first record the resistance value, and then measure the level 2 and level 3. Generally speaking, the larger the level measured, the greater the resistance between it and the capacitor line. For example, level 1 is 70 ohms .2 gear 110 ohm, 3 gear 150 ohm, etc. You can write it down and compare. In other words, if you measure the resistance of the above 3 gears are all infinite, or a certain gear is infinite, that is The motor coil is blown or the coil of a certain gear is broken. Finally, check whether the 5 wires and the motor casing, that is, the so-called ground, are short-circuited.
