Start-up procedure for a brushless, sensorless motor

Details Start-up procedure for a brushless, sensorless motor Start-up procedure for a brushless, sensorless motor

1992-10-30

1994-08-30

Wysocki, Jonathan

Electricity: motive power systems

Switched reluctance motor commutation control

318439, H02P 100

Patent

active

053431278

ABSTRACT:
A method for starting-up in a desired forward sense of rotation a multiphase, brushless, sensorless, DC motor, while limiting the extent of a possible backward rotation. First, a predetermined initial phase is excited (thereby accelerating the rotor toward an equilibrium position for that initial phase), for only a fraction of the time necessary for the accelerated rotor to travel through a nearest angular position which would determine a "zero-crossing" in the waveform of any one of the back electromotive forces (BEMFs) which are induced by the rotor on the windings of the motor. After the elapsing of this brief impulse of excitation, the sign of the BEMFs induced in the windings of the motor are digitally read thus producing a first reading. The occurrence of a first "zero-crossing" event is monitored, and, if this happens within a preset interval of time subsequent to the instant of interruption of the first excitation impulse, the optimal phase to be excited first for accelerating the motor in the desired direction is decoded through a look-up table, and the start-up process may proceed. If such a zero-crossing occurrence is not detected within said period of time, the routine is repeated by exciting a different phase, which is functionally shifted by two phase positions from the initial phase. The maximum backward rotation that may occur in the worst of cases is sensibly less than the angular distance which separates two adjacent equilibrium positions of the rotor and in practice may be of just few degrees.

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