Testing electric motors is now easier because there are powerful new testing equipment that can simplify the job and there is a lot of knowledge on how it can be done easily and quickly.
Because motors can have a lot of operational issues, it might not be obvious what the problem is when one fails to operate. For instance, there might be a variety of issues that have gone wrong if the equipment is not starting, runs intermittently or hot, or continually trips its over current probe device. The problem could be power supply, including the branch circuit conductors or a motor controller. Another cause is a jam on the driven load or is binding or mismatched.
The motor itself might become faulty when there is a burnt wire or connection, or when there is failure in winding including insulation deterioration, or a deteriorating bearing.
However, it is possible to quickly identify the common problems seen on these equipment by attaining a few basics on how to do the testing.
Usually, the ubiquitous multimeter is used to do the preliminary tests on motors, although there are a number of other diagnostic tools such as clamp-on ammeters, temperature sensors, a Megger or oscilloscope. The ubiquitous multimeter tester should be able to provide a diagnostic information for all kinds of motors.
Electric measurements: For an unresponsive motor or when there is no ac humming or false starts, you might want to take a voltage reading at the motor terminals and check if the voltage is dropped or if it is actually there. If none is there or it is reduced, check upstream by taking readings at any accessible points including disconnects, the motor controller, any fuses or junction boxes, and so on. Then check back to the over-current device output at the entrance panel. Check for the same voltage level as measured at the entrance panel main breaker.
The voltage reading should be the same at both ends of the branch circuit conductors if there is no electrical load. Again, the drop of this voltage should not be more than 3 percent of optimal otor efficiency if the circuit electrical load is close to the circuit capacity. If it is a three-phase hookup, the voltage reading should be same for all the legs. You could also roll the connections in order to equalize the voltage readings where the variation is by only a few volts.
However, make sure to avoid reversing the rotation. Just balance the three legs by matching the supply voltages and load impedances.
If the electric supply checks out, disengage the load and if this does not restore the operation, disconnect the power and attempt to turn the motor by hand. It should turn freely, otherwise, there is an obstruction inside or a seized bearing.
Tolerances are tighter for fairly new bearings and these are prone to seizure. That would be true if there is ambient moisture or when the motor has been unused for a while.
You can restore the operation by oiling front and rear bearings even without having to disassemble the motor.
Because motors can have a lot of operational issues, it might not be obvious what the problem is when one fails to operate. For instance, there might be a variety of issues that have gone wrong if the equipment is not starting, runs intermittently or hot, or continually trips its over current probe device. The problem could be power supply, including the branch circuit conductors or a motor controller. Another cause is a jam on the driven load or is binding or mismatched.
The motor itself might become faulty when there is a burnt wire or connection, or when there is failure in winding including insulation deterioration, or a deteriorating bearing.
However, it is possible to quickly identify the common problems seen on these equipment by attaining a few basics on how to do the testing.
Usually, the ubiquitous multimeter is used to do the preliminary tests on motors, although there are a number of other diagnostic tools such as clamp-on ammeters, temperature sensors, a Megger or oscilloscope. The ubiquitous multimeter tester should be able to provide a diagnostic information for all kinds of motors.
Electric measurements: For an unresponsive motor or when there is no ac humming or false starts, you might want to take a voltage reading at the motor terminals and check if the voltage is dropped or if it is actually there. If none is there or it is reduced, check upstream by taking readings at any accessible points including disconnects, the motor controller, any fuses or junction boxes, and so on. Then check back to the over-current device output at the entrance panel. Check for the same voltage level as measured at the entrance panel main breaker.
The voltage reading should be the same at both ends of the branch circuit conductors if there is no electrical load. Again, the drop of this voltage should not be more than 3 percent of optimal otor efficiency if the circuit electrical load is close to the circuit capacity. If it is a three-phase hookup, the voltage reading should be same for all the legs. You could also roll the connections in order to equalize the voltage readings where the variation is by only a few volts.
However, make sure to avoid reversing the rotation. Just balance the three legs by matching the supply voltages and load impedances.
If the electric supply checks out, disengage the load and if this does not restore the operation, disconnect the power and attempt to turn the motor by hand. It should turn freely, otherwise, there is an obstruction inside or a seized bearing.
Tolerances are tighter for fairly new bearings and these are prone to seizure. That would be true if there is ambient moisture or when the motor has been unused for a while.
You can restore the operation by oiling front and rear bearings even without having to disassemble the motor.
No comments:
Post a Comment