(1) external observation. Observe the winding end of junction boxes, with or without burning, overheating of the winding left Brown and smelly.
(2) research on temperature method. No-load running 20 minutes (when an exception is found should cease immediately), touch each of windings with the back part is above normal.
(3) the power test. Measured with a meter, if an excessive current, indicating that the short circuit.
(4) bridge inspection. Measurement of DC resistance of the winding, general difference should not exceed 5% above, if the resistance is small one-phase short circuit fault.
(5) short circuit detector method. Winding short circuit to be measured, the sheet steel may vibrate.
(6) method of a multimeter or ohmmeter. Any measurement of two-phase winding insulation resistance, minimal or zero reading indicates that the second-phase winding short circuit between phases.
(7) the voltage drop method. After series three-winding into the low voltage safety AC, reading small one group faults were detected.
(8) the current method. Motor no-load operation, measuring three-phase current, replacing the two-phase measurement and comparison, if we do not change with the power switch, the larger a winding short circuit current.