So messen Sie die Qualität des Motors mit einem Multimeter
The quality of the motor can only be preliminarily judged using a multimeter, which is to detect the coil resistance of the motor. But whether there are abnormalities in ground insulation and phase to phase insulation of the electric motor still needs to be judged by the corresponding voltage level insulation shake meter.
Firstly, for single-phase motors: To check with a multimeter, it is necessary to disconnect the capacitor to check the resistance values of the main and auxiliary windings of the single-phase motor. Generally, the resistance value of the main winding is relatively small, while that of the auxiliary winding is relatively large, usually consisting of three terminals. The resistance values can be measured separately, and under normal circumstances, the highest resistance value of the three can be obtained as the sum of the other two. The capacitor needs to be checked separately (the capacitor needs to be discharged first), and the multimeter can be directly measured by setting it to the capacitor mode.
Three phase motor: If it is a small three-phase motor with a star connection, the short-circuit wire can be removed first, and a multimeter can be used to measure the resistance values of the three coils in the resistance range. The resistance values are generally not very large, and the difference is not very large. The phase to phase and ground should be disconnected when tested with a multimeter. If there is unstable resistance jumping when checking with a multimeter, it is best to use the corresponding insulation shaker to confirm.
High voltage motor: The inspection of high-voltage motors requires professional tools to check, using a multimeter to determine which ones are prone to accidents.
The preliminary judgment of the quality of the motor is an essential step, and sometimes it is impossible to immediately disassemble the motor when a fault occurs. Therefore, preliminary judgment is also convenient for quickly finding the crux of the problem.
Judging the quality of the motor
Smell the smell on site, if you smell a burnt smell, it is likely that the motor is burnt out. There is a circuit phenomenon in the insulation measurement of the three-phase motor, which may cause a short circuit in the cable between the detection point and the motor. It is also possible that a certain phase terminal of the motor junction box is in contact with the housing. It is also possible for the internal insulation and shell contact of the motor.
The cable of the motor may have short circuits, as well as short circuits between the three-phase terminals and a series of short circuits between phases inside the motor. When measuring the three-phase insulation of a three-phase motor, it is possible that the cable between the measured point and the motor is damaged or broken, or the three-phase terminals of the motor fall off, or the internal winding of the motor is burned out and the neutral section of the motor is disconnected.
Measure the resistance values between each pair of the three phases of a three-phase motor, such as ab, ac, and bc. If the resistance values between them are too high, it indicates that the motor has three-phase imbalance and is likely to have burned out internally.
If the resistance between the neutral plate of the motor and the motor casing is zero, it is likely that at least one phase of the insulation layer has burned out, causing a ground short circuit in contact with the motor casing. Remove the neutral plate of the motor and measure the neutral point corresponding to one phase of the motor and the other end of the motor. If it is zero, it may cause internal burnout of the motor and result in wire breakage.
Many faults are unpredictable, and maintenance personnel can only make preliminary judgments. Specific problems need to be analyzed in detail, and it is inevitable that there will be some fragments of words.
I personally think it is difficult to achieve the desired effect of measuring motor insulation with a multimeter. Because the ohm range of a multimeter is too small, with a maximum range of only 10K Ω, and the minimum insulation between phases and to ground for three-phase or single-phase motors is not less than 0.5 megaohms (M Ω), 10k Ω is 10000 ohms, and 0.50 megaohms (Ω) is 50 million ohms (Ω). It seems that measuring motor insulation with or without a meter is really out of reach.
It is best to use a 500 volt (v) megohmmeter to measure the insulation of a 380 volt or single-phase motor, and sequentially measure the insulation and grounding of the three-phase (A, B, C) phases.
In the absence of a shaking meter, a multimeter can also be used to roughly measure. Even if the ohm 1OK range reaches infinity, it cannot be considered that the motor insulation is qualified. At this point, you can turn on the power to test the machine. When closing, you should close quickly and pull forcefully. When closing, you should observe the size of the electric arc flower, listen to whether the operating sound is normal, and whether there is vibration. If everything is normal, use a test pen to test whether the shell leaks electricity. Only after everything is normal can it be put into operation.
