| 摘要 |
PURPOSE:To reduce a decreasing rate in time in output current, by keeping all three-phase upper arm elements under OFF control, while three-phase lower arm elements are kept in each On or OFF control command state. CONSTITUTION:In a three-phase bridge as a DC/AC conversion unit, each switching element of three-phase arms U, V, and W is put under ON/OFF control in a way that a vector difference voltage between an inverter output voltage and a motor counter electromotive voltage is reduced to a minimum at the starting point of current limiting control over an increase in one of three-phase output currents Iu, Iv and Iw. That is, an inverter voltage at an optimum vector state according to a vector state of the motor counter electromotive voltage is obtained under the ON/OFF control on each switching element of the three- phase arms U, V, and W. As a result, a changing rate of current in time for each output current Iu, Iv, and Iw, can be relaxed under the current limiting control, and thereby a large pulsating current can be prevented, and stable output current control is carried out. |
