U.S. Philips Corporation

Jurgen Halfmann

Ekkehard Bolte

Matthias Wendt

Lutz Scholten

The invention relates to a brushless d.c. motor having a commutation circuit for the commutation of phase currents in order to generate a given commutation angle in a given mode of operation of the d.c. motor. In order to guarantee a satisfactory performance of the motor for all modes of operation the commutation circuit is switched between a plurality of modes in which different commutation angles are generated with a switching frequency which is substantially higher than the operating frequency of the motor. The invention is particularly suitable for the use in brushless d.c. motors for domestic appliances such as food processors.

Brushless d.c. motor

An electrical drive arrangement for an electric motor including a stator having a plurality of phase windings, and a rotor. The drive arrangement includes an electronic commutation circuit to supply electric power to the phase windings of the electric motor, a position sensor device, a phase control circuit coupled to receive the sensor signals and provide resultant sensor signals with a phase shift relative to the phase relationship of the sensor signals, a waveform generator coupled to receive the resultant sensor signals and provide commutation signals, and a control circuit coupled at least to the waveform generator for setting the amplitude and the phase shift of the electric power to be supplied to the motor. The phase control circuit includes a control signal generation circuit, a sensor signal allocation circuit, a delay time determining circuit, a sensor signal output circuit, and a load signal generating circuit. The drive arrangement enables the torque angle, i.e., the phase angle between the magnetic field generated in the stator and the rotor position, to be controlled in dependence upon the movement of the rotor using simple position signals and simple circuitry.

Electrical drive arrangement

A control circuit for controlling the speed and stopping time of an electronically commutated motor having a rotary drive member and a stator having at least one phase coil, electric power being supplied to the phase coils by current supply elements which are controlled by the control circuit to obtain a given phase voltage and a given load angle during operation. In response to a supplied stop signal the control circuit decelerates the drive member by controlling the phase voltage and load angle so as to produce a deceleration force which changes dependent on the speed of the drive member; there being a high speed range over which the deceleration force increases to a maximum value as speed is reduced; an intermediate speed range over which the deceleration force remains substantially constant at the maximum value as speed is further reduced, and a low speed range over which the deceleration force reduces as speed is still further reduced to a stop. The intermediate range adjoins the low range at a speed at which the deceleration force which would result from direct short-circuiting of the phase coils would substantially reach a maximum value. A significantly reduced stopping time can be obtained.

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Herzogenrath, Germany

Jurgen Halfmann