Hedge fund Aspex Management had urged Nidec to retain chief executive Mitsuya Kishida to help steer the Japanese electric-motor maker through an accounting crisis and potential restructuring, shortly before his unexpected resignation was announced, according to a report by Bloomberg.Aspex, which says it holds about 7% of Nidec, sent a letter to the company's board on 28 September calling for Kishida to remain in the top job, provided he was deem…