Brushless dc motor unit and method of driving the unit

Details Brushless dc motor unit and method of driving the unit Brushless dc motor unit and method of driving the unit

1995-09-08

1997-06-17

Martin, David S.

Electricity: motive power systems

Limitation of motor load, current, torque or force

318254, 388921, 388910, 388915, H02K 2300

Patent

active

056400730

ABSTRACT:
A brushless dc motor unit has 3-phase armature windings, a permanent-magnet rotor, a dc power supply having a motor drive voltage and a midpoint voltage that is one half of the motor drive voltage, and an electronic commutation circuit. Back emf voltages at armature winding terminals are individually delayed by less than 90.degree. and the delayed voltages are individually provided to the positive input terminals of voltage comparators. To the negative input terminals of the comparators is commonly provided a sawtooth-wave comparator reference voltage having a frequency proportional to a current rotor speed and an amplitude whose center voltage is the midpoint voltage. Outputs of the comparators cause a control circuit to transmit signals to control the electronic commutation circuit so as to provide 3-phase dc power to the armature windings. A basic reference voltage regulates the amplitude of the comparator reference voltage, and the value of the basic reference voltage can be changed according to a rotor speed or motor current so as to adjust the delay angle of the comparator outputs. The time constant of the phase delay circuits may be increased when the rotor speed is below a predetermined speed.

REFERENCES:
patent: 3670224 (1972-06-01), Jensen
patent: 3967173 (1976-06-01), Stitch
patent: 4511835 (1985-04-01), Studtmann
patent: 4743815 (1988-05-01), Gee et al.

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