Electric Motor Winding Testing

Ac motor winding resistance test.

Electric motor winding testing.

With a multimeter set to low ohms usually 200 test between each winding terminal and the metal casing of the motor. Most repair shops will use a megger or a ground insulation tester. Test electric motor windings when a bad motor winding cannot be found by a physical inspection many times an ohmmeter may show that there is a defective winding. Usace testing procedure cont 11 winding dc resistance test follow usace procedure three sets of results total a to b phase b to c phase c to a phase correct values to 40 c using the formula in step 8.

Power supply test for single phase motors the expected voltage is about 230v or 208v depending whether you are using the uk or america voltage system. To check the condition of the armature windings the armature will probably have to be removed from the motor. The reading ohms for each winding should be the same or almost identical. We ll start with a quick review of why testing is important followed by a discussion of rotor bar hipot surge and motor winding resistance as well as a discussion of vibration analysis.

The megger will help to detect areas of deteriorating insulation where the windings may soon short. Ac motor winding resistance test check the motor winding resistance or ohms reading with a multimeter. If windings are shorted together the electro magnetic fields cannot be created for that coil causing the motor to run erratically or fail all together. All values obtained from winding dc resistance test.

The meg ohm test has long been the tool of choice for most engineers and this simple test is often the only electrical test performed on a motor. If the winding s insulation wears away near the motor s case the bare wire winding shorts to ground. If there is any reading on any of these then the motor is bad do not use it. Record initial and corrected values on motor testing record sheet.

This includes testing the motor for grounded windings. Know that the three steps have identical or almost identical windings. Since there are three terminals. Bearing problems may be the number one cause of electric motor failure but electrical faults are a close second.

Check that the correct voltage is applied to the motor. You may find that when it runs ungrounded that the casing becomes live at up to supply voltage. However while the meg ohm test has a valid role to play it is simply not capable of detecting all the likely faults within a motor s winding. For phase to phase terminals u to v v to w w to u test the motor winding resistance or ohm reading using a multimeter or ohmmeter.