A manufacturer had been experiencing a series of unexplained breakdowns in small motors used in the manufacture of EV vehicles and other products that were sold a year ago. Although the motor was selling well, the manufacturer continued to receive reports of unexplained faults, mostly related to the failure of insulation. Viewing the matter seriously, the manufacturer’s executive launched a response, headed up by its quality assurance team, in order to identify the cause of the faults and implement solutions as quickly as possible.
The Problem
The cause was identified, but the new tests required to prevent it resulted in longer lead-times.
The batch of compact electric motors in question had been shipped after passing their electrical conformity assessments, which comprised of insulation resistance and voltage withstand tests.
An employee from the quality assurance division who was in charge of the tests recalls:
“The test results suggested that it was something else causing the insulation failures. After carefully checking all of the motor components used, we discovered significant deterioration in the insulation resistance of some of the major components.”
After further investigation, the employee discovered that most of the problems were attributable to voids forming in the insulation layer during the manufacturing process. During use, electrical charges would accumulate in these voids, causing the material’s insulating properties to be impaired.
To be certain, the employee contacted a specialist measurement organization, which advised him to conduct partial discharge testing. The two tests the company was currently conducting were unable to identify voids, so the team decided straight away to add partial discharge testing to its list of pre-shipment tests.
However, this caused another issue. This extra step in the testing process, involving the use of a dedicated partial discharge tester, made the testing process more complex, and also necessitated a separate power supply and testing cables, so the setup process also became quite troublesome. To make things worse, the team found that the need to spend more time testing had the effect of increasing production lead-time and reducing efficiency.
Partial discharge testing was essential in order to prevent faults before they arose. The employee and his team looked at ways of incorporating this test without affecting productivity but could think of no options whatsoever.
Key Aspects of the Problem
- The motor faults were caused by voids in the insulation that formed during the manufacturing process and could only be discovered with partial discharge testing equipment.
- The adoption of dedicated partial discharge testing equipment would have required extensive setup and additional labor, increasing lead-time.
