How to use a multimeter to measure the various motor bad or not bad
1, DC small motor
Hairdryer small motor through the bridge rectifier will be connected to the positive and negative in the small motor of the positive and negative staking head, the internal structure of this small motor is a wire wound on the rotor, through the contact turn on the winding coil cutting the magnetic lines of force, resulting in rotation, such a small motor can be used in the hair dryer, children's toys, recorders, vacuum cleaners and so on to see. The motor on the picture is borrowed from the AC, intercepted part of the voltage of the electric heating wire (6v), after rectification on the normal operation, if the rectifier is damaged and does not turn, the hair dryer is only hot and not out of the wind.
Open the hair dryer, revealing a cut motor electric pile head, first with a multimeter 10k resistance file were measured four diode pole phase, such as positive and negative phase are resistance value that is burned, and then measure the motor two pile head, if there is resistance, and then rotate the wind blades in the DC file to measure the voltage is not bad, I repaired!
2, three-phase motor
I have managed the dormitory area of the water tower, I designed an automatic control pumping device, because the AC contactor control of the three-phase on and off connection, because the contactor is a fake, there is no silver contacts, there is an item burned, due to the lack of items, the water in the deep wells are burned pan bubble, just with a multimeter measured tens of ounces of resistance between the three phases are equal, respectively, after the replacement of the contactor to try to send the power first, out of the water, and also work normally. Because the line outside the kind of insulated tube, 㓎 in the water to play a natural cooling cooling effect, otherwise away from the water has long been burned.
I repair motor and a master is a good friend, I want to wind what transformers need enameled wire are given to him, I often see him folded motor and then rewound, baskets of baskets of enameled wire windings were embedded into the motor line slot, you must put in the slot into the insulating paper, can not be touched with the steel, not to mention the line because of the installation of the broken insulating varnish, otherwise leakage of electricity between the turns of the motor will be burned. Installation of the slots of the coil should finally be connected into three-phase, lead three lines, with a meter measuring the resistance of the three-phase coil for an equal number of ohms to dozens of ohms (motor size), each line with the shell is absolutely no amount of resistance.
If people send the motor for repair, first smell, turn, most of them are overloaded and burned, some are not always open, bearing loss of oil rust operation is impeded, so that the motor overloaded burned, because no one supervise the bad to know. I have a motor in my old house is the loss of oil can not turn the bearings.
Don't just open the motor, smell the odor before measurement, the amount should be measured individually three-phase wire stakes resistance equal to be accurate, the general motor moisture may also be measured between the line and the shell to the resistance data.
