Apparatus and method for driving and controlling brushless motor

Details Apparatus and method for driving and controlling brushless motor Apparatus and method for driving and controlling brushless motor

1996-06-25

1998-04-14

Cabeca, John W.

Electricity: motive power systems

Limitation of motor load, current, torque or force

318453, 318254, 388813, H02P 602

Patent

active

057396515

ABSTRACT:
A brushless dc motor having 3-phase stator windings and a permanent-magnet rotor is driven on a dc voltage through a 3-phase electronic switching circuit. Back emf voltages across the stator windings are individually phase-delayed and the phase-delayed voltages are individually compared in comparators with a common sawtooth-wave comparator reference voltage having a frequency proportional to a current rotor speed and an amplitude whose center voltage is one-half of the motor driving dc voltage. A drive control unit, a microcomputer, transmits to the switching circuit switching control signals in sequential driving steps according to 3-phase output signals of the comparators so that the switching circuit performs commutation of the motor drive voltage in a first motor driving mode. The time constant of the phase-delay circuits is increased when the rotational speed of the rotor is below a predetermined speed or the motor driving current is above a predetermined level. When the time constant is increased, the motor driving mode is switched from the first motor driving mode to a second motor drive mode for a predetermined time period at fixed driving steps regardless of the 3-phase comparator output signals. The motor driving mode reverts to the first motor driving mode when the predetermined time period for the second motor driving mode has lapsed.

REFERENCES:
patent: 5319289 (1994-06-01), Austin et al.
patent: 5461293 (1995-10-01), Rozman et al.
patent: 5619109 (1997-04-01), Cameron et al.
patent: 5640073 (1997-06-01), Ikeda et al.

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