Control arrangement and system comprising this control arrangement and an inverter for induction motor speed controller.

摘要

An inverter control apparatus comprises a first current level setting unit (5) which sets a protection level for switching elements included in an inverter (1), and a second current level setting unit (7) which sets a current level that prevents a stall torque point slip from being exceeded and that is determined in association with the load characteristic of an induction motor (2) and a voltage/frequency ratio being presently delivered. Either smaller current level is selected by a current level selector (8), to control a frequency so as to lower or to stop rising lest the slip frequency of the level current should be exceeded. Thus, whatever voltage/frequency ratio is set to drive the motor or whatever induction motor is connected, the motor can operate in a stable region without stalling or without damaging the switching elements.