Patent ID: 9590544
Date: 2017-03-07
CPC Classifications: H02P

Claim:
1. A method for operating an electric motor, which is connectable via a switching device to a current source and which is connected in parallel with a freewheeling device, the method comprising: applying control to the switching device at a specific activation ratio within each working cycle to establish a desired effective operating voltage of the electric motor, so that in at least one operating mode each working cycle is made up of an activation time period and a freewheeling time period, wherein the applying control to the switching device includes switching the switching device to a conductive state during the activation period in order to supply current to the motor via the switching device, wherein the freewheeling device includes a freewheeling transistor and a freewheeling diode connected in parallel with the freewheeling transistor, wherein the freewheeling diode is reverse-biased with respect to the current source; at a conclusion of the activation time period, interrupting a connection between the motor and the current source by switching the switching device into a nonconductive state; and while the connection between the motor and the current source is interrupted during the freewheeling time period, applying control to the freewheeling transistor in the freewheeling time period by identifying a freewheeling voltage dropping across the electric motor when the freewheeling transistor is in a nonconductive state, and by switching the freewheeling transistor into a conductive state for a specific switching time period if the freewheeling voltage is less than zero.