Minebea Company, Limited

Klaus Moosmann

Martin Winker

A method for starting a multiphase, sensorless commutated, brushless electric motor. The method has three operating phases. A start-up phase in which the motor is operated from a standstill with specified commutation times. An acceleration phase in which the motor is accelerated up to a nominal speed, wherein the commutation times are determined on the basis of the zero crossings of the BEMF voltage of the non-energized stator phase windings. And a stationary operating phase in which the nominal speed is kept constant. The transition from the start-up phase into the acceleration phase takes place when, during the start-up phase, a predetermined number of successive zero crossings of the BEMF voltage in the expected order in the expected motor phases have been identified. The transition from the acceleration phase into the stationary phase takes place once the nominal speed has been reached.

Method for operating a brushless electric motor

The invention describes a method for controlling a sensorless, brushless DC motor that is controlled via a bridge circuit preferably using pulse width modulation (PWM) having precommutation. According to the invention, in the braking operation each commutation interval is divided into two phases. A drive phase, lasting from the start of the commutation interval up to zero crossing in which the motor is controlled with the normal PWM, and a braking phase, lasting from zero crossing up to the next commutation time in which at least two motor phases are short-circuited and/or in which the PWM is operated with recovered energy. The efficiency of the control circuit is as low as possible so as to ensure that the braking energy is consumed in the control circuit.

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Schramberg, Germany

Klaus Moosmann