Sensorless commutation method

A circuit arrangement for rotor-position-sensorless commutation of an EC motor, preferably for sinusoidal commutation of a rotor-position-sensorless EC synchronous machine in a stepless continuous process from startup to stationary operation of the motor, wherein the circuit arrangement is for acquisition of terminal values of the motor, is connected to said motor, and comprises:

• at least one Clarke-Park transformer for the transformation of the terminal values into a d/q observer coordinate system rotating synchronously with the rotor of the motor;
• a detector which is designed for a determination of minimum signal values for activation of a coordinate system correction;
• an observer for estimating an EMF (electromotive force);
• and
• a PLL structure for orienting the observer coordinate system, wherein
• the PLL structure comprises a phase regulator and an oscillator, for regulating an angular offset ΔθB via a frequency input of the oscillator;
• the phase regulator assigning a direction of rotation as a function of a mathematical sign of a q component of the EMF;
• and
• the phase regulator limiting output rotation frequency to within a corresponding range of positive or negative values,
• wherein the detector activates the phase regulator of the PLL structure for the coordinate system correction as soon as a system-specific threshold value for current or voltage amplitudes is exceeded.