Electricity: motive power systems – Limitation of motor load – current – torque or force
Patent
1998-06-17
1999-12-14
Masih, Karen
Electricity: motive power systems
Limitation of motor load, current, torque or force
318254, 318138, 318139, 318599, 318432, H01R 3946
Patent
active
060022264
ABSTRACT:
A brushless DC motor modifies motor commutation events to reduce noise by providing overlapping activation of the switch being deactivated with the switch being newly activated so that three switches are temporarily activated. The newly activated switch is pulse width modulated with a motor torque controlling duty cycle, and the switch being deactivated is pulse width modulated synchronously with the newly activated switch but with a duty cycle decreasing from the torque controlling duty cycle. The decreasing modulation of the switch being deactivated allows a slower current decrease in the phase turning off to reduce or eliminate the disturbances, and thus the noise. The decreasing modulation is preferably exponential in manner, with a time constant varying inversely with motor speed so that the duty cycle reaches a predetermined minimum in a predetermined maximum number of motor electrical degrees. The decreasing modulation may be switched on at low motor speeds where its noise reduction is required and switched off at higher motor speeds where the potential for interference with commutation is greater. The decreasing modulation is applicable in a dual switching mode in which each activated switch, except for the switch being deactivated in commutation, is pulse width modulated at the torque controlling duty cycle, or in a modified single switching mode in which the activated switch of one of the upper or lower groups is always closed continuously during its activation, except for commutation, during which the switch remaining on, which alternates between the groups, is closed continuously. Each mode of operation is applied in the motor speed/torque region to which it is best suited.
REFERENCES:
patent: 4551708 (1985-11-01), Welburn
patent: 5793183 (1998-08-01), Carobolante et al.
Unitrode Integrated Circuits "Modelling, Analysis and Compensation of the Current-Mode Converter" U-97, undated.
Unitrode Integrated Circuits "Linear Integrated Circuits--Brushless DC Motor Controller IC" UC1625/UC3625 dated Dec. 5, 1988.
IEEE/KTH "Brushless DC Motors with Low Torque Ripple" by M. Lajoie-Mazenc, J.M. Vinassa, J. Cros, S. Astier Stockholm Sweden, Jun. 18-22, 1995.
Collier-Hallman Steven James
Kleinau Julie Ann
Skellenger Dennis B.
Anderson Edmund P.
General Motors Corporation
Masih Karen
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