2 Minute Tech Note Testing a Servo Motor Part 1 Electrical

How servo motors are tested at Repair Zone.  There are several electrical and mechanical tests that a servo motor must go through

to determine the overall health of the motor.  All major components are tested independently and as a whole unit.  In part 1, we will take a look at the electrical testing.

The first test, is the Megger test.  This is used to check if the motor is grounded.  But it also can tell you how good the insulation system is.  If the test shows low Megs, the motor may still be good, it may just need to be washed and baked.  Then, it would be Megger tested again before assembly.

Next is the Surge Test.  The surge test is a test used to determine the dielectric strength of the insulation from turn to turn and phase to phase, in a coil or winding.  This is done by using the surge tester and testing all 3 phases of the motor.  While under electrical load, we monitor the wave-form patterns and look for a balanced wave-form on each phase which tells us that it is good.  If the phase is bad, the wave-form is unbalanced and can contain a straight line or an erratic look to it.  In this case, the phase is good.

While performing the Back EMF test, we find out the magnetic strength of the rotor by spinning the servo motor at 1,000 rpm.  If the reading is within 10% of OEM spec, the rotor is magnetically good.  If it reads at or below - the rotor would need to be replaced.

In ‘Testing a Servo Motor’ Part 2, we will look at the mechanical side of testing.

 “And that is your 2-minute Tech Note from Repair Zone”