Diagnosticado un fallo en el dinamómetro de una planta de automoción

Description

Location: Midwest Truck Transmission Manufacturing Plant Dynamometer Motor: 200 horsepower, special motor and dynamometer drive, 480 volts Systems Affected: Final inspections in process, 8% of capacity affected Cost of failure: > $125,000 in equipment, not including production, delivery, and labor Savings: > $500,000 in equipment, not including production, delivery, and labor.

A specialized dynamometer system failed at a Midwestern truck transmission factory during the final testing phase of its production line. The failure damaged over $125,000 worth of sensitive drive equipment during production, resulting in an unexpected 8% shutdown of the final testing production area.

Initial readings

The ALL-TEST IV PRO 2000 was applied to determine the cause of the fault. The first test was performed at the Motor Control Center (MCC) and indicated a severe short circuit (I/F and phase angle) and loose connections (resistance).

According to standard practice, the motor was tested in the motor junction box with the following good results:

This indicated that the fault lay in the wiring. Upon inspection, it was discovered that the connections had been improperly crimped, resulting in a loose connection that caused the wire insulation to rupture and fail. The fault was a direct short circuit that caused catastrophic damage to the unit. Note that the wire was not grounded.

Next step

An analysis of the motor circuit (ACM) had not been performed on the dynamometer system prior to the cable failure. The system was included in the plant’s reliability program, and other dynamometer cables were found to be in the same condition. A short circuit was detected in the coil of a dynamometer motor (150 hp).

The final testing stage is very critical, so the Reliability Department added an acceptance test stage to all new and rebuilt dynamometer motors. An example of a good test for a new 200-horsepower dynamometer motor is as follows:

Avoid costs

Early detection and correction of the other faults resulted in cost savings, in equipment alone, of at least $500,000 compared to the failures that occurred in the same way as with the first 200-horsepower dynamometer. Each dynamometer failure reduces the plant’s production capacity by 8% during the final testing phase.

Lessons learned

A review of the plant’s critical motors would identify the critical equipment that should be included in the reliability program. Motor circuit analysis, using ALL-TEST IV PRO 2000, can provide input inspection capabilities, trend analysis, and troubleshooting of unusual problems in predictive maintenance equipment. Identifying loose connections, cable faults, and winding problems typically leads to a quick and easy return on investment for the program.