The EKG of Motor Health: Megger (Insulation) Testing
A servo motor might look fine when checking coil resistance with a multimeter. But if it instantly throws an "Overcurrent" or "Earth Fault" when connected to a drive, the issue is invisible insulation tears. The only way to detect this is the Megger Test (Insulation Resistance Test).
Why Does Insulation Weaken?
Coolants (boron oil) seeping into the motor, overheating, or poor-quality wire varnish melt the insulation around copper wires over time. Wires start touching each other or the motor housing (chassis).
How is a Megger Test Performed?
While a multimeter outputs max 9V, a Megger applies 500V or 1000V DC high voltage to the windings. It measures the resistance (in MegaOhms) between phases and ground. If the value is low, insulation has collapsed, and rewinding is mandatory.
Guaranteed Stator Winding Lab
In our lab, rewound motors are subjected to Megger tests again after Class-H insulation and Vacuum Pressure Impregnation (VPI) processes to prove their integrity.