Motor drive having invertor
First Claim
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1. A motor drive for driving a motor at a variable speed, the motor having a rotor and a plurality of phase coils, comprising:
- a d.c. power source for supplying a d.c. power;
an invertor for receiving the d.c. power from said d.c. power source and converting the d.c. power to variable frequency a.c. power, the variable frequency a.c. power being supplied to said plurality of phase coils;
commuting means connected between said d.c. power source and said plurality of phase coils for allowing commuting currents to flow back to said d.c. power source from said plurality of coils when said rotor is decelerating;
control means for controlling said invertor so that said rotor rotates at the variable speed with the variable frequency a.c. power supplied by said invertor to said plurality of phase coils, said control means further controlling said invertor so that the commuting currents circulate as flywheel currents between said invertor and said plurality of phase coils when the commuting currents fall below a predetermined level;
first detecting means for detecting currents flowing in said plurality of phase coils and outputting first detection signals indicative of the currents flowing therein; and
determining means for determining that the currents flowing in said plurality of phase coils fall below the predetermined level, wherein said control means controls said invertor based on a determination made by said determining means.
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Abstract
A motor drive includes an invertor (5) with which a motor (6) is rotated at a variable speed. To suppress noises caused by ripple components contained in currents flowing in phase coils of the motor, the invertor (5) is controlled so as to direct a commuting current flowing from the phase coils to a d.c. power source (1) and at a time when the motor is decelerating to circulate in a path including the phase coils and the switching transistors of the invertor (5). This control is performed when the commuting currents fall below a predetermined level.
29 Citations
19 Claims
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1. A motor drive for driving a motor at a variable speed, the motor having a rotor and a plurality of phase coils, comprising:
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a d.c. power source for supplying a d.c. power; an invertor for receiving the d.c. power from said d.c. power source and converting the d.c. power to variable frequency a.c. power, the variable frequency a.c. power being supplied to said plurality of phase coils; commuting means connected between said d.c. power source and said plurality of phase coils for allowing commuting currents to flow back to said d.c. power source from said plurality of coils when said rotor is decelerating; control means for controlling said invertor so that said rotor rotates at the variable speed with the variable frequency a.c. power supplied by said invertor to said plurality of phase coils, said control means further controlling said invertor so that the commuting currents circulate as flywheel currents between said invertor and said plurality of phase coils when the commuting currents fall below a predetermined level; first detecting means for detecting currents flowing in said plurality of phase coils and outputting first detection signals indicative of the currents flowing therein; and determining means for determining that the currents flowing in said plurality of phase coils fall below the predetermined level, wherein said control means controls said invertor based on a determination made by said determining means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A motor drive for driving a motor at a variable speed, the motor having a rotor and a plurality of phase coils, comprising:
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a d.c. power source for supplying a d.c. power; an invertor for receiving the d.c. power from said d.c. power source and converting the d.c. power to variable frequency a.c. power, the variable frequency a.c. power being supplied to said plurality of phase coils; commuting means connected between said d.c. power source and said plurality of phase coils for providing current paths from said plurality of phase coils to said d.c. power source; and control means for controlling said invertor so that said rotor rotates at the variable speed with the variable frequency a.c. power supplied by said invertor to said plurality of phase coils, said control means further controlling said invertor so that regenerative currents generated from said plurality of phase coils when said rotor is decelerating flow back as commuting currents to said d.c. power source through said commuting means when the regenerative currents are above a predetermined level and that the regenerative currents circulate as flywheel currents between said invertor and said plurality of phase coils when the regenerative currents fall below the predetermined level. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification