MITSUBISHI ELECTRIC CORPORATIONPUBLIC RELATIONS DIVISION

7-3, Marunouchi 2-chome, Chiyoda-ku, Tokyo, 100-8310 JapanFOR IMMEDIATE RELEASE

No. 3512

Customer Inquiries

Media Inquiries

Marketing Department
Transmission & Distribution Systems Center
Energy & Industrial Systems Group
Mitsubishi Electric Corporation

Public Relations Division

Keiden_Ako_Tr@ym.MitsubishiElectric.co.jp
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Mitsubishi Electric Corporation

Notice Regarding Improper Quality Control Practices
for Transformers Rated 22kV 2MVA or AboveTOKYO, April 21, 2022 – Mitsubishi Electric Corporation (TOKYO: 6503) announced today that internal
investigations being conducted by the external Investigative Committee established by the company on July2, 2021, revealed to the company on April 1 that several inspections of transformers rated 22kV 2MVA orabove manufactured at Mitsubishi Electric’s Transmission & Distribution Systems Center in Ako, Hyogo
Prefecture, did not fully comply with customer-requested testing standards that required compliance with theJapan Electrotechnical Committee (JEC), International Electrotechnical Commission (IEC), or Institute ofElectrical and Electronics Engineers (IEEE) standards. The Investigative Committee also confirmed cases
where improper statements were entered in inspection reports. In addition, several designs were found to differ
from internal-design guidelines or agreements with customers.
Mitsubishi Electric halted shipments of the products in question as soon as the issues were disclosed tocompany management. Currently, only those products confirmed to have been inspected properly are being
shipped. Customers using the products in question are now being notified of the situation. To this date, thecompany has not received any notification by the customers regarding the improper quality control practices.
Mitsubishi Electric is willing to implement special inspections of the products in field upon discussion withcustomers.
The committee’s investigation of the Ako factory is still ongoing and Mitsubishi Electric will publicly
announce any other serious matter, including possible improper quality control practices of other products, ifidentified hereafter.
The root cause of these incidents as well as new measures to prevent any recurrence will be announced as soon
as the Investigative Committee issues its final report. Meanwhile, Mitsubishi Electric is continuing tocooperate with the committee to help it complete its investigations as soon as possible.

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At present, Mitsubishi Electric has determined that there is no need to revise its consolidated earnings forecast
for the current fiscal year. The company, which is working sincerely with customers and implementing
necessary preventive measures, will disclose any potential impact on consolidated earnings forecast that comesto light hereafter.
Products in Question
Transformers (22kV 2MVA or above)
Total units: 8,363 shipped from 1982 to March 2022
(6,035 units delivered to customers in Japan & 2,328 units to customers overseas)
Total units subjected to any improper practice [1) – 4) below]: 3,384(1,589 units delivered to customers in Japan & 1,795 units to customers overseas)
Discrepancies Identified (as of April 21, 2022)
1)

Dielectric Tests
Dielectric tests were conducted at lower voltages than specified by the JEC, IEC or IEEE standard, but
voltages required by the standard or customers were entered in test reports. Also, reported results of partial
discharge measurements conducted simultaneously with these tests were not accurate.

2)

Temperature Rise Tests
Measured temperatures exceeded the maximums specified by the JEC, IEC or IEEE standard orcustomers, but temperatures below the maximums were entered in test reports.

3)

Load Loss Measurements
Measured load losses exceeded guaranteed values, but values within the guarantees were entered in test
reports.

4)

Insulation, Temperature and Load Loss Designs
Insulation designs: Designed voltages were lower than those specified in internal design guidelines basedon the IEC or IEEE standard.
Temperature designs: Designed temperatures were higher than those specified in the internal design
guidelines based on the IEC or IEEE standard.
Load loss designs: Designed load loss value exceeded those previously guaranteed with customers.
###About Mitsubishi Electric Corporation
With 100 years of experience in providing reliable, high-quality products, Mitsubishi Electric Corporation(TOKYO: 6503) is a recognized world leader in the manufacture, marketing and sales of electrical andelectronic equipment used in information processing and communications, space development and satellite
communications, consumer electronics, industrial technology, energy, transportation and building equipment.
Mitsubishi Electric enriches society with technology in the spirit of its “Changes for the Better.” The company
recorded a revenue of 4,191.4 billion yen (U.S.$ 37.8 billion*) in the fiscal year ended March 31, 2021. For
more information, please visit www.MitsubishiElectric.com*U.S. dollar amounts are translated from yen at the rate of ¥111=U.S.$1, the approximate rate on the Tokyo
Foreign Exchange Market on March 31, 2021

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