| Step | Expected Result/Action |
|---|---|
| 14. Check a three-phase compressor motor for winding-to-winding shorts or partially shorted windings as follows: Because of the extremely low resistance values being measured, an accurate VOM/DMM must be used to perform this step, otherwise a good compressor may be judged as bad. Connect the VOM/DMM across the leads connected to the compressor terminals T1 and T2, then measure and record the resistance as shown in Figure SP-9-18. Repeat the resistance measurements between the leads connected to compressor terminals T2 to T3 and T3 to T1. | VOM/DMM indicates a measurable resistance across each winding. As a rule of thumb, the motor windings are usually judged to be good if the resistance measured across each winding is nearly identical to that of the other two windings. Example 1 Assume that the resistances measured across the three windings are 5 ohms, 4.99 ohms, and 5. J ohms. In this example, the motor windings would be judged to be good because the three motor resistances are nearly identical. Example 2 Assume that the resistance measured across the three windings are 5 ohms, 4.99 ohms, and 3.0 ohms. In this example, the motor windings would be judged to be partially shorted because one of the resistances (3.0 ohms) is significantly different than the other two. |
