One of the Mitsubishi Electric Corp. transformers in question was in question after it emerged on April 21 that testing of the units had been falsified for decades. Mitsubishi Electric Corp. has admitted to four decades worth of fraudulent testing and improper design of electrical transformers used in nuclear power stations, thermal plants and substations that power trains.
The company, which has been plagued by other revelations of testing fraud over the past year that forced high-level resignations, has announced the latest discovery of misconduct on April 21.
The large-size transformers in question were manufactured at the company's factory in Ako, Hyogo Prefecture.
Between 1982 and March 2022, Mitsubishi Electric shipped 8,363 transformers from the factory. About 40 percent of those, or 3,384, were fraudulently tested or improperly designed.
1,589 of the 3,384 problem transformers were shipped within Japan, while 1,795 were sent overseas.
The names of clients that received these transformers are not known by the company.
In some cases, the company s employees falsified figures in quality-testing reports, which said the unit's internal temperature remained within limits during heat tests. The temperature actually rose above the limits during these tests, but the company admitted on April 21 that it actually rose above the limits.
The safety tests conducted by the factory were to see how much voltage the units could withstand, but did not meet acceptable test conditions set by international standards or by academia.
The voltage levels of some transformer insulators were lower than what the company had determined based on international standards.
The charges will be conducted to see if the misconduct was in violation of the Electricity Business Law.
The misconduct wouldn't lead to transformer breakdowns or accidents, the company said. It is considering contacting each buyer individually and replacing components if necessary.
Mitsubishi Electric has been embroiled in a scandal for many months over the discovery of fake inspection reports and design errors on other industrial equipment it makes, from electronic toll collection equipment to air conditioners.
The discoveries began last year at one of the company's factories in Japan, starting with one in Nagasaki Prefecture.
The chairman and president of the company resigned last year to take responsibility.
Since then, the company has stressed its commitment to preventing this from happening again.
A committee of external lawyers looking into testing irregularities at the company made the latest discovery of misconduct on April 1.
The committee is not sure when its investigation will be completed, because it is taking much more time than originally thought. It had previously maintained that the investigation would come to a close around the end of April.