Current chopping in switched reluctance drive systems
AssigneeSwitched Reluctance Drives Limited
InventorsMichael James Turner, Charles Richard Elliott
Life of this patent
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Abstract
A switched reluctance drive is supplied from a power source and has a DC link capacitor. The phases of the machine are controlled by a current chopping controller which, during phase conduction overlap, controls the initiation of chopping in a second phase so as to minimize the current drawn from the capacitor, thereby allowing a reduction in the capacitor rating.
Claims20
A controller for a polyphase switched reluctance machine supplied with supply current from a voltage bus having a DC link capacitor connected across the voltage bus, the controller comprising:
- means for producing first and second unidirectional chopping currents from the supply current for energizing first and second phases of the machine in sequence according to a demand input;
- and
- means for phase shifting the second chopping current for the second phase with respect to the first chopping current for the first phase when excitation of the two phases is coincident, whereby current ripple in the DC link capacitor is reduced.
A switched reluctance drive system for controlling a switched reluctance machine supplied with supply current from a voltage bus having a DC link capacitor connected across the voltage bus, the system including a controller, comprising:
- a switched reluctance machine;
- means for producing first and second unidirectional chopping currents from the supply current for energizing first and second phases of the machine in sequence according to a demand input;
- and
- means for phase shifting the second chopping current for the second phase with respect to the first chopping current for the first phase when excitation of the two phases is coincident, whereby current ripple in the DC link capacitor is reduced.
A method of reducing current ripple in a DC link supplying current to a polyphase switched reluctance machine, said DC link comprising a voltage bus and a DC link capacitor connected across the voltage bus, the method comprising:
- producing first and second unidirectional chopping currents from the supply current for energizing first and second phases of the machine in sequence according to a demand input;
- and
- phase shifting the second chopping current for the second phase with respect to that for the first phase when excitation of the two phases is coincident, whereby current ripple in the DC link capacitor is reduced.
A controller for a polyphase switched reluctance machine, comprising:
- means for producing first and second chopping signals for energizing first and second phases of the machine in sequence according to a demand input;
- and
- means for phase shifting the second chopping signal for the second phase with respect to the first chopping signal for the first phase when excitation of the two phases is coincident;
- wherein the controller further includes, for one of the phases, means for producing clock signal output, delay means for producing delayed clock signal output, and selector means, the chopping signal for the one phase being derived from the clock signal output and being switchable between the clock signal output and the delayed clock signal output, the selector means being arranged to select between the clock signal output and the delayed clock signal output for phase shifting the chopping signal for the one phase.
A method of reducing current ripple in a dc link of a polyphase switched reluctance drive, the method comprising:
- producing first and second chopping signals for energizing first and second phases of an electrical machine in sequence according to a demand input;
- and
- phase shifting the second chopping signal for the second phase with respect to that for the first phase when excitation of the two phases is coincident;
- wherein the phase shifting is performed by selecting between the at least first and second chopping signals for one of the phases when excitation of the two phases is coincident.
A method of reducing current ripple in a dc link of a polyphase switched reluctance drive, the method comprising:
- producing first and second chopping signals for energizing first and second phases of an electrical machine in sequence according to a demand input;
- phase shifting the second chopping signal for the second phase with respect to that for the first phase when excitation of the two phases is coincident;
- storing values of delay associated with at least one monitored parameter of the drive;
- and
- setting the phase shift of the second chopping signal according to the stored value of the delay.
A method of reducing current ripple in a dc link of a polyphase switched reluctance drive, the method comprising:
- producing first and second chopping signals for energizing first and second phases of an electrical machine in sequence according to a demand input;
- phase shifting the second chopping signal for the second phase with respect to that for the first phase when excitation of the two phases is coincident;
- calculating a phase shift value from at least one monitored parameter of the drive;
- and
- setting the phase shift of the second chopping signal according to the calculated value.
Dependencies are inferred from the claim text.