At a large battery separator plant, the number of motor trouble calls seemed high. While discussing this with the plant electrical engineer, a senior electrician said he often found high resistance across motor lead connections.
After disassembling the problem connections, he performed insulation resistance tests on the windings. Next, he used solderless connectors for safe temporary connections so he could observe the running motor and take vibration readings. If no problems emerged, he then made the permanent connections.
The written procedure for motor maintenance (including replacement) required all three-phase motor connections to be bolted. On smaller motors, connections were sometimes made by other means. Larger motors had the required lugs, but per this electrician, compression lugs sometimes “had no die marks and were just squished with pliers.”
This discussion led to that electrician’s conducting a one-on-one “show me” session with each of the plant’s 14 other electricians. This exercise revealed that two electricians involved in motor work did not know how to test connection resistance or how to select the proper crimping die for a given connection. Training to qualify those workers would have prevented many improper repairs.