Nsk Corporation

Shinichi Tanaka

Toru Sakaguchi

Yuzuru Hoshi

Sachio Nakayama

Masanori Shingou

An electric power steering apparatus that protects Zener diodes without impairing steering performances by time-integrating a loss power of the Zener diodes for protecting FETs and gradually limiting a duty ratio with an increase in an integrating loss. The apparatus includes a loss power calculating section that calculates a loss power when a difference between an ignition voltage and an inverter applying voltage is equal to or more than a predetermined voltage; an integrating loss calculating section to calculate an integrating loss of the loss power; a permissible loss calculating section to calculate a permissible loss based on a temperature; a minimum value selecting section to select a minimum value of a loss difference of the permissible loss and the integrating loss; and a limit value calculating section to calculate a limit value of the PWM-signal based on the minimum value of the loss difference and the permissible loss.

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Maebashi, Japan

Shinichi Tanaka