Device for determining a position of a rotor of an electric motor

摘要

A device for determining a rotor position in a polyphase electric motor has a power control unit for applying drive voltages according to a pulse width modulation scheme so as to synchronously drive the motor. A measurement unit is arranged for measuring a voltage value on a respective phase by determining a zero-crossing interval where the phase current is around zero, disconnecting the phase from the respective drive voltage during the zero-crossing interval, and measuring the voltage value when the drive voltage of a first other phase is the supply voltage and the drive voltage of a second other phase is the zero voltage. A position unit is arranged for determining the rotor position based on the voltage value.

主权项

1. A device for determining a rotor position in a polyphase electric motor having stator coils comprising three phases, the device comprising:
a power control unit configured to apply drive voltages on each of the three phases, wherein the drive voltages comprise drive pulses alternating between a zero voltage and a supply voltage according to a pulse width modulation scheme so as to generate sinusoidal phase currents in each of the phases for synchronously driving the motor; a measurement unit arranged for measuring a voltage value on a respective phase by
determining a zero-crossing interval where the respective phase current is around zero,disconnecting the respective phase from the respective drive voltage during the zero-crossing interval,determining at least one measurement interval in the zero-crossing interval where the drive voltage of a first other phase is the supply voltage and the drive voltage of a second other phase is the zero voltage, andmeasuring the voltage value during the measurement interval; a position unit configured to determine the rotor position based on the voltage value, wherein the measurement unit is arranged for initiating the zero-crossing interval based on detecting the respective phase current being below a predetermined threshold.