Method and apparatus for controlling a switched reluctance machine
AssigneeEmerson Electric Motor Co.
InventorAlan P. French
Life of this patent
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Abstract
A method for controlling the average voltage applied to a phase winding of a reluctance machine during periods of current increase, stable current control, and current decrease to improve machine efficiency and thereby reduce acoustical noise produced by the machine and unwanted vibration. According to one aspect, a method is provided whereby a maximum duty cycle is selected and voltage is applied to the phase winding during the period of current increase according to the maximum duty cycle until the current reaches a desired peak current value and thereafter the voltage applied to the phase winding is equal to the lesser of the voltage required to keep the phase current at the predetermined peak current value or the voltage corresponding to the maximum duty cycle.
Claims19
A method for controlling the rate of current change in a phase winding of a reluctance machine from a level of approximately zero current towards a predetermined peak current value, the phase winding being coupled by a power switching device to a source of available DC voltage, the method comprising the steps of:
- establishing a fixed chopping frequency for applying voltage pulses to the phase winding where the interval between the initiation of adjacent voltage pulses defines a first time interval;
- selecting a maximum active interval for applying the DC voltage to the phase winding, the maximum active interval corresponding to a percentage of the first time interval that is less than 100%, the maximum active interval defining a maximum net average voltage for application to the phase winding,
- applying the available DC voltage to the phase winding to initiate a voltage pulse when the rotor reaches a predetermined angular position with respect to the stator such that the current begins to increase from a level of approximately zero towards the predetermined peak current value;
- monitoring the current in the phase winding and comparing a representation of the current in the phase winding with a representation of the predetermined peak current value;
- and
- removing the application of the available DC voltage from the phase winding at a time corresponding to the earlier of:
- (i) a time when the phase current reaches the predetermined peak current value;
- or
- (ii) the time when the percentage of the first time interval defined by the maximum active interval has passed since the initiation of the voltage pulse.
A method of reducing noise in a switched reluctance machine system including a reluctance machine having a rotor and a phase winding, the method comprising the act of controlling the rate of change of magnetic flux in the machine during an interval when the phase current rises from a value of approximately zero amps to a desired peak current value by:
- establishing a fixed chopping frequency for applying voltage pulses to the phase winding where the interval between the initiation of adjacent voltage pulses defines a first time interval;
- selecting a desired maximum time interval, where the desired maximum time interval is less than the first time interval;
- applying voltage to the phase winding to initiate a voltage pulse;
- and
- removing the application of voltage from the phase winding at a time corresponding to the earlier of:
- (i) a time when the phase current reaches a desired peak current value;
- or
- (ii) the time when the maximum time interval has passed since the initiation of the voltage pulse.
A method of reducing noise in a switched reluctance machine system including a reluctance machine having a rotor and a phase winding, the method comprising the act of controlling the rate of change of magnetic flux in the machine during an interval when the phase current rises towards a maximum current value, the method comprising the steps of:
- establishing a fixed chopping frequency for applying voltage pulses to the phase;
- selecting a maximum time interval, the maximum time interval being less than the time interval between adjacent voltage pulses;
- applying voltage to the phase winding to initiate a voltage pulse;
- and
- removing the application of voltage from the phase winding to terminate the voltage pulse at a time corresponding to the earlier of:
- (i) a time when the phase current reaches the maximum current value;
- or
- (ii) the time when the maximum time interval has passed since the initiation of the voltage pulse.
Dependencies are inferred from the claim text.