Surge-free switching-on of inverter to 3 phase asynchronous machine - using current desired value-current actual value comparison across search current regulator

摘要

The determination of the synchronism of teh inverter and the three-phase asynchronous machine is carried out using the comparison of a current desired value and a current actual value across a search current regulator. With an inverter, which normally presupposes a stator voltage, across a rotor flux oriented voltage model of the three phase asynchhronous machine, as well as the corresp. phase position of this voltage. A magnetising current regulator (6) reacts to correct the voltage model, for compensating the non-linearity, whilst a rotor current regulator (3) reacts on the stator frequency to be specified corresp. to the load requirement, with both regulators getting their actual values from a current actual value computer (7). The current regulator is used as a search current regulator, to which is specified the current desired value zero with faded out magnetising and rpm regulators, thereby specifying any selectable starting frequency, for the inverter. The inverter is operated by the voltage model with a reduced output voltage, until the current actual value has reached a min. value. With the reaching of this min. value, the frequency value established is used, for initiating the operational type control of the three phase asynchronous machine. USE/ADVANTAGE - Type method which uses far less costly synchronising circuit for surge free connection of three-phase machine to inverter.