General Electric Company

Stephen R MacMinn

James Patrick Lyons

Charles Michael Stephens

Mark A Preston

Paul Michael Szczesny

Gerald Burt Kliman

Peter B Roemer

Fred G Turnbull

James W Sember

Anantha Krishnan Pradeep

A commutator for an electronically commutated machine provides a microprocessor-based mechanism for translating discrete samples of machine angular rotor position information, either measured or determined indirectly, into commutation signals. Commutation control is achieved with shaft position information available only at discrete time instants, which are not, in general, the required commutation times. A filter and state observer provide estimates of the mechanical states of the rotating machine, i.e., angular position, velocity and acceleration. In one embodiment, a Kalman filter of variable gain is used for estimating the mechanical states. In another embodiment, a sliding mode observer is used for estimating the mechanical states. In the preferred embodiment, a combination of a sliding mode observer and a steady state Kalman filter is used to obtain the mechanical state estimates; the Kalman filter with small constant gains provides smooth tracking of a steadily rotating machine, while the sliding mode observer provides fast acquisition during transient conditions.

Microprocessor-based commutator for electronically commutated motors

A rotor position estimator for a switched reluctance motor (SRM) employs a flux-current map to determine whether the actual rotor angle is closer to, or farther from, axial alignment of stator and rotor poles than a reference angle .theta..sub.r. The flux-current map is a plot of reference flux .PSI..sub.r as a function of current for the reference angle .theta..sub.r. If a flux linkage estimate .PSI..sub.i is greater than the reference flux .PSI..sub.r, then the actual rotor angle is closer to alignment than the reference angle .theta..sub.r, and the flux-map comparator output is a logic level one. If the flux linkage estimate .PSI..sub.i is lower than the reference flux .PSI..sub.r, then the actual rotor angle is farther from alignment than the reference angle .theta..sub.r, and the flux-map comparator output is a logic level zero. When the result of the flux comparison causes the flux-current map comparator to change state, the actual rotor angle is equal to the reference angle .theta..sub.r, with the result that phase currents can be successfully commutated relative to this rotor position. The flux-current map can be implemented using either single-phase or multi-phase SRM flux-current characteristics.

Discrete position estimator for a switched reluctance machine using a

A lock detector for a switched reluctance motor (SRM) position estimator monitors the rotor angle estimates from a SRM rotor position estimator to make sure that the estimator is accurately tracking rotor position. Phase flux and current measurements corresponding to the rotor angle estimate of the sampled phase are supplied to dividing circuitry which generates a phase inductance estimate. The phase inductance estimate is compared by logic circuitry to lower and upper inductance limits to determine whether the rotor angle estimate falls within a specified tolerance of a theoretical inductance value. Alternatively, a flux-current map is used to generate a phase flux reference for comparison to the phase flux estimate. A lock detector flip-flop is reset whenever the phase inductance estimate (or phase flux estimate) is outside the specified tolerance, and a signal is sent thereby to disable the SRM.

Lock detector for switched reluctance machine rotor position estimator

A method and apparatus for indirectly determining rotor position in a switched reluctance motor (SRM) are based on a flux/current model of the machine, which model includes multi-phase saturation, leakage, and mutual coupling effects. The flux/current model includes a network mesh of stator, rotor and air gap reluctance terms. The network is driven by magnetomotive force (mmf) terms corresponding to the ampereturns applied to each of the stator poles. Phase current and flux sensing for each phase are performed simultaneously. The reluctance terms of the flux/current model are determined from the phase flux and current measurements. The phase current and flux measurements also determine the rotor position angle relative to alignment for each respective motor phase and which phase (or phases) is operating in its predetermined optimal sensing region defined over a range of rotor angles. The measurements on at least two phases are then used for establishing whether the stator phases of the sensing phase are approaching alignment or maximum unalignment with SRM rotor poles. Finally, the rotor position angle for the sensing phase and its position relative to alignment are used to provide a rotor position estimate for the motor.

Rotor position estimator for a switched reluctance machine using a

A method and apparatus for indirectly determining rotor position in a switched reluctance motor (SRM) are based on instantaneous flux and phase current sensing. For each phase in a predetermined sequence of phase sensing, which depends on the particular quadrant of machine operation, phase flux and phase current measurements are made during operation in a pair of predetermined sensing regions each defined over a range of rotor angles. Rotor angle estimates are derived from the flux and phase current measurements made during the sensing region for each respective phase. The rotor angle estimates for each phase are normalized with respect to a common reference and then used to generate a rotor position estimate for the SRM.

Rotor position estimator for a switched reluctance machine

Apparatus for estimating torque generated by a switched reluctance machine utilizes a ROM table look-up scheme to generate a torque estimate based upon phase current and rotor position information. Each ROM address is accessed by digitizing and then combining sensed phase current and rotor position signals. Knowledge of the instantaneous torque output enables closed-loop torque control including appropriate adjustments of phase currents to reduce or eliminate torque pulsations.

Torque estimator for switched reluctance machines

A microcomputer-based drive system for a switched reluctance motor requires no rotor position sensor and no discrete current sensors. Phase excitation is synchronized with rotor position by indirectly estimating rotor position according to instantaneous phase inductance. Current regulation is achieved by incorporating pilot devices for current sensing into the switching devices of the power converter and by employing a fixed off-time current chopping strategy. One application is for use in a laundering machine.

Switched reluctance motor drive system and laundering apparatus

A method and apparatus for improving the operation of a switched reluctance motor at low speed incorporates an advance angle regulator which regulates the firing angle of current pulses to the switched reluctance motor so that over a wide range of speeds and levels for direct current source voltages, the winding current reaches a commanded set point at a commanded angle. The advance angle regulator may comprise a closed loop regulator which includes apparatus for detecting the actual angular position at which motor current reaches a commanded level and adjusts the turn-on angle to shift the angle at which current reaches its desired level to a desired angle. The regulator incorporates a feedforward portion and an integral portion. The feedforward portion is utilized primarily to accommodate situations in which there is no current feedback. The integral portion provides the primary regulation when current is regulated to its desired value. The regulator causes the torque versus current command to have a transfer function which does not depend upon speed or DC source voltage over a wide range of speed, voltage and torque.

Control system for low speed switched reluctance motor

A method and apparatus are provided for controlling the switching devices in a switched reluctance machine bridge inverter having at least two switching devices per phase. One switching device is used for hysteresis band current chopping to regulate phase current magnitude, while the other switching device, in combination with a flyback diode, provides a circulating path for phase current. Alternatively, current chopping and circulating are alternated between both switching devices during each conduction interval of the corresponding machine phase. Ripple current is decreased, thereby reducing the required size of the DC link capacitor. Switching losses are also reduced.

Current chopping strategy for switched reluctance machines

A fault management system for a switched reluctance motor detects faults through phase current differential sensing and phase flux differential sensing and isolates any fault by deactivating any faulted phase. Motor operation continues through the remaining phases. A speed control circuit maintains the normal operating speed of the motor, despite the deactivation of one or more phases. Starting the motor when stopped in a 'dead zone' created by a faulted phase is accomplished by using the intact phases to generate negative torque to move the rotor out of the dead zone.

Fault management system for a switched reluctance motor

An indirect position estimator for a switched reluctance motor applies short duration, low level sensing pulses to two unenergized phases of the motor. A change in phase current during a sampling period, resulting from the application of the sensing pulse, is sensed and processed to produce an indication of a pair of estimated angles for each of the unenergized phases. A pair of angles for one such unenergized phase is shifted by a value equal to the phase displacement between the two unenergized phases and the shifted angles are then compared to the angles of the second phase to determine which angles match. The matching angle is produced as a signal indicative of the estimated instantaneous rotor position. If any stator phase changes state during the sampling period, or if the two initially unenergized phases do not remain unenergized throughout the sampling period, a signal corresponding to an extrapolated rotor position is produced instead of the signal indicative of estimated instantaneous rotor position. Extrapolation preferably includes a least squares recursive estimation, with exponential forgetting, of speed.

Rotor position estimator for switched reluctance motor

A commutator for a microcomputer based switched reluctance drive employs a selectively addressable non-volatile memory, e.g. a ROM, to store stator phase firing patterns and facilities selective adjustment of turn-on angle and pulsewidth of phase switching current pulses. Firing patterns differing only in pulsewidth of their respective pulses can be stored in different sections of the memory or in the same section where word bit width permits. The adjustment of pulse position and duration allows torque control of the motor over a very wide speed range.

Commutator for switched reluctance drive

A reluctance motor is started from standstill and accelerated to the rated speed of the motor without using a shaft position sensor. In this type of reluctance drive, if the motor fails to start and loses synchronism with the stepping commands, the resulting average current drawn by the motor will exceed the current drawn if the motor were in synchronism. If such excessive current is sensed, the starting sequence is re-tried.

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Schenectady, NY, United States of America

Stephen R MacMinn