How to measure the AC contactor coil with a multimeter?
Judge the good and bad contactor coil can be measured by multimeter resistance to judge, general contactor coil organization in a few hundred ohms, if you measure the organization is very small (such as a few ohms, and power does not suction) that is the coil short-circuit; if the organization is very large (such as infinity) that is the coil broken.
Also check the voltage of the coil going into the contactor to prevent the coil from not engaging because the screws are not tightened, or the contactor from not engaging because the wire going into the contactor coil is disconnected.
Measure the coil with a digital multimeter with an ohm rating of 2K or less to see if the coil is disconnected, and if it is disconnected, prove that the coil is bad.
Use the multimeter ohm 200 to measure the normally closed and normally open (measuring normally open by hand or electrified suction) auxiliary contact pass or not, if the contact contact contact is not good, this time the measurement resistance is very large. Indicates that the contact contact is not good, if the auxiliary contacts are connected to the load, when measuring the voltage, the voltage will not reach the rated voltage.
Use a multimeter to measure the normally open and closed terminals to see if it is normal, the coil is not good with a multimeter, the best way is to directly add the rated voltage into the test action.
Measurement method to determine the fault of three-phase asynchronous motor with multimeter simply
1: turn-to-turn short circuit The multimeter is adjusted to the ohm gear, and each winding is measured to detect whether the three-phase winding is equal in resistance value (actually there is a deviation, but the deviation is very small). For star-connected motors, measure the first end of the winding and the common end. For motors with delta connection, measure the first and last ends of each winding. If one of the three-phase windings has a much smaller resistance value relative to the others, then it can be determined to be a turn-to-turn short. If there is only a deviation, but the deviation is not large, but there is some doubt, it is recommended to measure with a bridge. Bridge in the measurement accuracy is much higher than the multimeter, the multimeter can only do a rough judgment of the turn-to-turn short-circuit. ps: motor winding three-phase resistance value deviation ≤ ± 5%, the measurement of the motor to be kept in a stationary state.
2: winding to ground short-circuit, winding shell, measure the insulation resistance between the winding and shell or ground, if zero or very small resistance, then you can judge the winding to ground short-circuit, the winding shell. If greater than 1M normal. PS: multimeter only do rough judgment, it is recommended to use the shaking table for retesting.
3: turn-to-turn circuit breakage, winding burnt Measure the resistance of each winding, if it is infinite or the resistance value is very large (much larger than the normal winding resistance value), then it should be turn-to-turn circuit breakage or winding burnt PS: turn-to-turn circuit breakage, winding burnt to dismantle the motor in order to determine.
