METHOD FOR CHANGING AN OPERATING STATE OF AN ELECTRIC MACHINE AND DEVICE FOR CHANGING THE OPERATING STATE OF AN ELECTRIC MACHINE

摘要

The present invention relates to an apparatus and a method for changing the operating state of an electric machine in a free-wheeling mode in which a significant over-voltage rise can be prevented. In the free-wheeling mode, the individual phase connections of the electric machine are electrically isolated from each other to change the electric machine to a safe operating state. According to the present invention, only a part of the phase current of the electric machine is evaluated. Based on the evaluated phase current, a suitable time for separation of the phase connection is determined for phase separation of all phase connections, i.e. phases for which the phase current is not evaluated.