Abstract: 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.

Abstract: In an active magnetic bearing system employing radial or thrust bearings, rotor shaft position is determined without requiring air gap position sensors, resulting in a high reliability system. The flux paths for each respective electromagnetic force actuator of the active magnetic bearing are isolated in order to minimize the magnetic coupling therebetween. The active magnetic bearing system is controlled for mutually exclusive excitation of each of the two actuators (e.g., stator pole pairs) per control axis. A sequence of test voltage pulses is applied to the unexcited one of each actuator pole-pair. At the peak of an applied test voltage pulse, after a predetermined time interval, the pole flux linkage is estimated using either an analog or software integrator. The integrator is reset at zero current, and hence zero flux, thereby avoiding accumulation of errors.

Abstract: In an active magnetic bearing system employing radial or thrust bearings, rotor shaft position is determined without requiring air gap position sensors, resulting in a high reliability system. The flux paths for each respective electromagnetic force actuator of the active magnetic bearing are isolated in order to minimize the magnetic coupling therebetween. In this way, the current (or magnetomotive force, mmf) in each respective actuator is functionally related to the flux therethrough, independent of the currents (or mmf's) in adjacent actuators. Application of a digital PWM pole voltage waveform during normal bearing operation results in a ripple current waveform at the PWM switching frequency. The resulting change in stator pole current and pole voltage are measured, and the average differential inductance is determined therefrom.

Abstract: A fault tolerant active magnetic bearing has at least three magnetically isolated control axes. To this end, the active magnetic bearing has a segmented stator which employs non-magnetic sections for magnetically isolating adjacent electromagnetic force actuators, and hence adjacent control axes. As a result, operating force actuators are not affected by magnetic poles experiencing a fault. Hence, in a three-phase active magnetic bearing rotor suspension control system, for example, full control of rotor shaft position can be maintained with only two functioning control axes.

Abstract: An auxiliary quasi-resonant dc link (AQRDCL) converter is employed to achieve soft-switching in an inverter coupled to a dc supply via a resonant dc link circuit. The resonant dc link circuit generates a quasi-resonant voltage to the inverter via a resonant bus. The dc link circuit includes upper and lower capacitors coupled to series between the positive and negative rails of the dc supply, respectively, with the voltage across the lower capacitor being controlled to be greater than the voltage across the upper capacitor. In this way, the need for a switch shorting the resonant bus to ground during a resonant cycle is avoided. An auxiliary switching device assists resonant operation of the resonant bus to zero voltage in order to provide a zero-voltage switching opportunity for the inverter switching devices as the inverter changes state.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A sealed oxygen container having a filling neck is provided with a heat welded closure cap. A valve is positioned within the neck. The valve enables the container to be filled with oxygen and then seals the oxygen therein preventing oxygen from escaping during heat welding of the closure cap. The heat welded cap may then be readily pierced so that oxygen can be dispsensed.

Abstract: A cogeneration system including a heat engine driving an electrical generator coupled to electrical lines at a site serviced by a utility is disclosed. The system includes supervisory means for monitoring the electrical energy and/or power supplied by the generator, supplied to the site by the utility, and consumed by site electrical loads, for storing monitored electrical data, and for controlling operation of the engine and generator in response to the monitored data. The system further is provided with data representing the energy and power rate structure of the local utility, and with a real time clock, and stores monitored electrical data and controls operation of the system in accordance with whether the time corresponds to a utility peak, intermediate, or off-peak energy rate period or to a peak demand measuring period. The system further comprises means for monitoring the thermal energy transferred from the engine to a site thermal load by heat exchange means.