BLDC MOTOR NOISE REDUCTION USING CONSTANT BUS CURRENT CONTROL COMMUTATION

WIPO Patent Application WO2002027912

A3

A motor control system (20) creates a rounding effect on square wave phase currents which results in reduced acoustic noise. The control system (20) includes a voltage sources (30) for providing a DC bus current, and an inverter (40). The inverter (40) has a switching (42) for regulating the DC bus current to a fixed level. The switching circuit (42) also forces consecutive phases of the motor (22) to share the bus current at commutation. Forcing consecutive phases of the motor (22) to share a desired amount of the DC bus current creates a "rounding" effect on the phase currents, which results in reduced acoustic noise. The preferred inverter (40) has a plurality of transistors, (Q1 - Q6) and a control module (46). The control module (46) selectively engages the transistors (Q1 - Q6) such that each phase of the motor (22) has a phase turn-on point that occurs before a phase turn-off point of a preceding phase. The control module (46) also pulse width modulates the transistors (Q1- Q6) such that the DC bus current is regulated to the fixed level. The result is a motor control system (22) and method that is less expensive and produces less acoustic noise than conventional noise.

CLARK BRET S
THORN STEPHEN J

PCT/US2001/042279

August 15, 2002

September 20, 2001

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EMERSON ELECTRIC CO (US)

H02P6/00; H02P6/08; (IPC1-7): H02P6/14; H02M1/12; H02P6/10

US5191269A	1993-03-02
US5955851A	1999-09-21
US5780986A	1998-07-14
US5793169A	1998-08-11
US5847521A	1998-12-08
US5869946A	1999-02-09

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