CONTROLLING SYSTEM OF OUTPUT CURRENT FOR FREQUENCY CONVERTER DEVICE

摘要

PURPOSE:To reduce a variation in gain in a control system by a method wherein the power factor of a load is decreased by supplying a predetermined amount of reactive current from a power factor changing means in a region increasing the intermittent degree of an output current at low level. CONSTITUTION:A positive-polarity current and a negative-polarity current are supplied to a load L such as an AC machine from a thyristor bridge A and a thyristor bridge B respectively and the currents are controlled by a control circuit PC in accordance with the polarity of a command value i*. At that time, the torque current component value i2* of the motor L is supplied to a power factor changing signal generator 10 and a power factor changing signal DELTAi1* is generated to add a magnetizing current component command value i1* and a magnetizing current component command value (i1*)' is generated. Therefore, the power factor of the load is decreased at a low-load current region and the level of th command value is increased to reduce a variation in gain of a control system by eliminating a current intermittent phenomenon and stable control can be performed.