Patent EP0780966A2 successfully refreshed from Google Patents.
EP0780966A2
Expired / Lapsed
EP
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Sensorless rotor position monitoring in reluctance machines
Assignee: Nidec SR Drives Ltd
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Filing: 1996-11-27
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Granted: —
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Expires: 2016-11-27
Abstract
Abstract A method of monitoring rotor position in a reluctance machine comprises determining the rate of change of current at a particular point at which current in the winding is arranged to freewheel. Preferably the point coincides with alignment of a rotor and a stator pole such that the rate of change of current is predicted to be zero. The magnitude and polarity of any variation from the predicted rate of change indicates a rotor position removed from the actual rotor position and whether it is in advance of, or retreated from, the predicted position. <IMAGE>
Inventors
- 👤 Stephen James Watkins
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 07:19
CPC Classifications
H; H02; H02P; H02P6/00; H02P6/14; H02P6/16; H02P6/18; H02P25/00; H02P25/02; H02P25/08; H02P25/086; H02P25/089
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
145 words
A method of monitoring rotor position in a reluctance machine comprising a stator, a rotor, which is moveable relative to the stator, and at least one phase winding mounted on the stator, the method comprising: moving the rotor relative to the stator; energising the phase winding by actuating switch means to control the current in the winding; freewheeling in each phase inductance cycle so that current in the winding recirculates for an interval at an estimate of a predetermined position of the rotor at which the rate of change of phase current is at a predicted magnitude; monitoring the phase current during freewheeling; comparing the monitored rate of change of phase current with that predicted at the predetermined position; and deriving the position of the rotor relative to the predetermined position from the difference between the actual and predicted rates of change of phase current.
Claim 2
Dependent Claim
26 words
A method as claimed in claim 1 in which the interval is coincident with a period of substantially no change in current as the rotor moves.
Claim 3
Dependent Claim
28 words
A method as claimed in claim 1 or 2, including sampling the current at or near the start and at or near the end of the freewheeling interval.
Claim 4
Dependent Claim
25 words
A method as claimed in claim 3 including calculating the rate of change of current from the change of current over the period of sampling.
Claim 5
Dependent Claim
29 words
A method as claimed in claim 1, 2, 3 or 4 in which the extent of the interval is inversely dependent on the speed of movement of the rotor.
Claim 6
Independent Claim
36 words
A method as claimed in any of claims 1 to 5 in which the difference between the actual and predicted rates of change of current is used to modify the estimate for a subsequent phase cycle.
Claim 7
Dependent Claim
41 words
A method as claimed in claim 6 in which the machine is a multi-phase machine having a phase energisation sequence, the difference between the actual and predicted rates being used to modify the estimate for the next phase in the sequence.
Claim 8
Independent Claim
24 words
A method as claimed in any of claims 1 to 7, including monitoring the freewheeling current at the switch means carrying the freewheeling current.
Claim 9
Independent Claim
20 words
A method as claimed in any of claims 1 to 7, including monitoring the freewheeling current at the phase winding.
Claim 10
Dependent Claim
130 words
A rotor position indicator for a reluctance machine having a rotor, a stator and at least one phase winding, the indicator comprising: a current monitoring device for deriving a signal indicative of phase current in the phase winding; switch means actuatable to configure a freewheel circuit in which current recirculates through the winding; timing means for actuating the switch means to configure the freewheel circuit for an interval coincident with a predicted range of rotor position, and for sampling the phase current to measure the rate of change of current in the interval; comparator means for comparing the predicted rate of change of phase current with the measured rate of change to derive a difference value indicative of the difference between the actual rotor position and the predicted rotor position.
Claim 11
Dependent Claim
34 words
An indicator as claimed in claim 10 in which the timing means are responsive to a signal indicative of the speed of movement of the rotor to vary the period in inverse relation thereto.
Claim 12
Dependent Claim
31 words
An indicator as claimed in claim 11 in which the timing means are responsive to the difference value to adjust the actuation of the switch means in a subsequent phase cycle.
Claim 13
Independent Claim
135 words
A system for monitoring rotor position in a reluctance machine, comprising a rotor, a stator, at least one phase winding, switch means operable to configure the phase winding in a freewheel circuit in which a freewheel current recirculates in the winding, a current monitoring device for deriving a signal indicative of freewheel current, timing means for actuating the switch means into the freewheel configuration for an interval at an estimate of a predicted position of the rotor at which the rate of change of current has a predicted value, means for deriving a measurement of the rate of change of current from the monitoring means in the interval, and means for calculating the position of the rotor relative to the predetermined position from a comparison of the actual and predicted rates of change of current.
Claim 14
Dependent Claim
25 words
A system as claimed in claim 13 in which the interval is arranged to be coincident with a period of substantially no change in current.
Claim 15
Dependent Claim
45 words
A system as claimed in claim 13 or 14 in which the means for deriving a measurement of the rate of change of current include sampling means for sampling the current at or near the start and at or near the end of the interval.
Claim 16
Independent Claim
42 words
A system as claimed in any of claims 13 to 15 in which the timing means are operable to modify the estimate for a subsequent phase cycle in response to the difference between the actual and predicted rates of change of current.
Claim 17
Dependent Claim
47 words
A system as claimed in claim 16 in which the machine is a multi-phase machine having a phase sequence wherein the timing means are operable to modify the estimate for the next phase in the sequence in response to the difference between the actual and predicted rates.
References Cited (Backward Citations)
No citation records indexed.
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