Abstract: A scheme for determining the stator resistance of an alternating current motor includes the determination of the actual flux of the motor through the sensing of motor voltage and motor current. The motor current is also utilized to develop a signal representing the anticipated motor flux which will result from that current. These two flux signals are combined to develop a flux error signal, the polarity of which is determined by whether the motor is in the motoring or regenerative mode of operation, which in turn is integrated to give the signal representing the motor stator resistance. Additionally, when the motor changes mode of operation, there is provided a step function which assures a motor stator resistance value being used which insures control stability.

Abstract: A system, for use with a controlled current inverter to prevent malfunction of inverter action resulting from an insufficient capacitor voltage to effect commutation of an inverter bridge controlled rectifier, provides that the capacitor voltage is sensed and, if it is of insufficient value to effect rectifier commutation, the application of gating signals to the next to be rendered conductive controlled rectifier is inhibited. In order to achieve initial inverter operation, the inverter current is also sensed and the inhibit function is rendered ineffective until such time as the current reaches a predetermined value.

Abstract: A load commutated inverter synchronous motor drive system wherein a thyristor firing control of the inverter is determined by the amplitude of pesudo flux waveforms which are derived from the integral of the line voltages coupling the inverter to the motor being driven. A firing strategy is provided based on the premise that optimum thyristor firing in a load commutated inverter operating at a leading power factor occurs at a point just below the peak of the forthcoming pseudo flux waveform which point comprises an amount of volt-seconds necessary to effect current commutation plus a nominal safety margin. The determination and control is implemented, preferably, in a software phase lock loop but can, when desirable, be implemented in hardware.

Abstract: A scheme for providing an output signal approximating a true sine wave representative of a sine wave source voltage from corrupted line voltages connecting the source to a load includes the development of a first signal representative of the corrupted lines line voltage. The first signal is then filtered to reject all but higher frequency components and this filtered output is then combined with the first signal to provide a combined signal which is further filtered to provide a final output signal.

Abstract: A control system for a load commutated inverter AC synchronous motor drive provides an operational shift in the event of an increase in motor terminal voltage V.sub.TERM above a preselected reference level. Under such an increase in terminal voltage, control is transferred from a condition where torque is controlled by current and the terminal voltage is uncontrolled to a condition where the load current, e.g., the DC link current I.sub.L flowing between a source side thyristor converter (AC to DC) 12 and a load side thyristor inverter (DC to AC) 14 is utilized to control the motor terminal voltage while the firing angle of the thyristor inverter 14 is used to control the motor torque. This involves increasing the minimum load or motor drive current for a desired torque while adjusting the inverter firing angle from a previous value, so that the desired torque is provided at a higher current I.sub.L and lower terminal voltage V.sub.TERM than before.

Abstract: For protection against commutation failures in a motor control circuit, there is provided a method and apparatus by which the charge on a commutating capacitor is made to track the armature current of a separately excited motor regardless of the operating mode of the motor. In preferred form, a commutating network is provided having a commutating capacitor, a charge reversal thyristor, and a commutating thyristor configured to cause commutation of a main, control thyristor upon sequentially gating the charge reversal thyristor and the commutating thyristor with charge of sufficient magnitude stored on the capacitor. The thyristors of the commutating network are gated according to the operating mode of the motor; thus, there is included a means, or step, for sensing the motor operating mode.

Abstract: The load side converter or inverter in a load commutated inverter motor drive, including a source side AC to DC converter coupled to a DC to AC converter via a DC link circuit, is adapted to have at least three and preferably four modes of operation for bringing an AC motor load, and more particularly a synchronous motor, up to speed. In the preferred embodiment, the first mode constitutes an idle mode wherein the converter thyristors are maintained in a non-conducting state until commanded for normal operation. The second mode constitutes an initial start-up mode which assumes no knowledge of initial rotor position of the motor and simply utilizes a fixed low frequency firing signal to sequentially gate the thyristors using forced commutation to commutate the off-going thyristor.

Abstract: A twelve-pulse control current inverter system having two six-pulse powered channels connected to a source of variable dc current is selectively operable to control either a three-phase motor or a double three-phase motor. Signals representing the phase currents of each of the two channels are combined with direct and quadrature motor flux signals, the latter signals being shifted in phase in the case of the double three-phase motor, to produce torque signals representing the motor torque produced by each of the two powered channels. These two torque signals are then combined to provide a total torque signal which, in turn, is utilized in the development of an angle signal for the control of the two current inverters.

Abstract: Apparatus disclosed for regulating a substantially constant magnetic flux level in an electromagnetic contactor. In one form a flux sensing device mounted in the contactor magnetic circuit provides a linear signal indicative of the level of magnetic flux in the contactor. A linear amplifier utilizes the flux signal to regulate contactor excitation to maintain flux at a desired value. In another form digital flux sensing device switches between first and second states as the level of magnetic flux varies between first and second values. A contactor excitation circuit "chops" the contactor excitation in response to the sensing device to thereby maintain magnetic flux at a value varying between the first and second values.

Abstract: Flux signals suitable for use in a control of an ac motor are generated as a function of the voltages and currents furnished to the motor. From sensed values of motor phase voltages and currents, signals representing the direct and quadrature values of motor voltage and current as well as total motor current are developed. Employing a closed loop path, these signals are utilized to develop signals representing the direct and quadrature components of the value of motor flux. The closed path develops a resistance signal representing the instantaneous motor resistance as a function of the total motor current and flux which resistance signal is employed in the development of the various flux signals.

Abstract: A current limiter for a load commutated inverter-synchronous motor drive including a source side AC to DC converter (12) and a load side DC to AC converter (14) coupled via a DC link circuit including an inductor (16) wherein a torque reference signal (TORQUE REF) generated for controlling both the converters is limited in response to the peak value .psi..sub.MAX of the pseudo flux waveform (.psi..sub.ab, .psi..sub.bc, .psi..sub.ca) which is derived from the integral (.intg.) of the motor terminal voltage (v.sub.ab, v.sub.bc, v.sub.ca) in order to limit the motor stator current I.sub.s to a value corresponding to the region of peak output torque T.sub.MAX obtainable for the motor field current I.sub.f applied. Control of both the source side converter (12) and the load side converter (14) by the torque reference signal operates to control the magnitude of the current I.sub.L in a DC link circuit which corresponds to the motor stator current I.sub.

Abstract: A current regulator for a dc electric traction motor propelled vehicle, implemented using a microcomputer, incorporates an accelerator response characteristics of an accelerator in an internal combustion engine powered vehicle. The regulator uses a current feedback loop to regulate motor torque to the value called for by the accelerator. However, of the magnitude of voltage as a percentage of available source voltage required to generate the desired current exceeds the percentage displacement of the accelerator, the applied voltage is limited to the percent accelerator displacement.

Abstract: A system and method are disclosed for automatically machining a work piece to precise selectively determined dimensions under computer numerical control in which the cutting tool is set automatically and automatic on-machine inspection is performed of the machined work piece surfaces. Using vibration sensing to detect contact between the cutting edge of the cutting tool and position reference surfaces, the cutting edge is calibrated against these surfaces under closed loop control. The deviation between the programmed and the actual positions of the cutting edge at each reference surface is determined and an initial compensating tool position offset is automatically provided in each axis and is entered into numerical control means. After machining has been initiated, probing of the work piece occurs at least once before the final cut is taken.

Abstract: A control system for powering an AC load such as a polyphase synchronous motor having at least two sets of three phase (3.phi.) windings. Each three phase winding set is powered by an independently operable six pulse load commutated inverter drive including a source side converter and a load side converter coupled together by means of a DC link and wherein the source side converter and the load side converter are operated in accordance with respective current and load angle regulators which respond to torque command signals generated by speed regulators.

Abstract: A control system for a separately excited DC electric traction motor in an electrically powered vehicle incorporates a plurality of current limit functions designed to protect both the motor and control electronics. A time dependent current limit is utilized to permit overcurrent conditions for limited time intervals such that additional power can be obtained for sudden torque requirements without having to design the motor or control electronics to function under continuous high torque conditions. The continuous current limit values based on percent conduction time of a thyristor chopper circuit in the control system is modified in response to overheating of the motor and the main switching thyristor, to overvoltage on the thyristor commutating capacitor and to available voltage for powering the motor.

Abstract: An electrical braking circuit provides smooth transitioning between regenerative and plug braking of a DC electric motor by use of a low ohmic value resistance path to maintain motor torque during transitioning. During initiation of electrical braking, a similar low ohmic resistance path momentarily connects the motor to a power source in order to establish proper magnetic flux in the motor to enable regenerative braking. Both resistance paths are disabled during motoring and braking modes of operation in order to minimize power loss in the resistance paths.

Abstract: A control system for an AC motor drive including a source side converter and a load side converter coupled together by means of a DC link circuit wherein the current in the DC link circuit is controlled by either the source side converter or load side converter depending upon which converter is capable of control. This is achieved by crosstieing a signal from the normal regulating path in the source side converter control to the alternate regulating path in the load side converter control. This signal is chosen to be indicative of the source side converter controller being unable to control current, and may be derived from current error. This signal operates to alter the firing angle of the load side thyristor bridge to regulate the DC link current in the event the source side converter is unable to maintain the required current regulation.

Abstract: A low dissipation snubber for switching power transistors uses the energy stored in a snubber capacitor to provide all the base boost power required for switching the power transistors on. The snubber consists of a diode and a snubber capacitor connected in series between the collector and emitter of the switching transistors with a resistor connected at one end to the junction of the diode and the snubber capacitor. The other end of the resistor is connected to the base turn-on circuit for the switching power transistors so as to provide a discharge path for the snubber capacitor. By using the discharge of the snubber capacitor, power which is normally dissipated as heat is reclaimed so that the drive power requirements for the switching power transistors are reduced.

Abstract: A pulse shaping and amplifying circuit receives direct current electrical power from a source and serves to supply a pulse of electrical energy to a load. First and second switches (e.g., transistor switches) are interconnected such that only one is conductive at any one time. The first switch, when conductive serves to connect a capacitor which forms part of an oscillatory circuit, further including an inductor in the form of a transformer primary winding, to the source to place an electrical charge on that capacitor in a first direction. When the second switch is rendered conductive (and the first opened) the load is connected in circuit with the oscillatory circuit and the capacitor discharges to deliver a pulse of electrical power to the load with any excess power being utilized to charge the capacitor in the second direction.

Abstract: An overvoltage protection circuit for a circuit array including one or more semiconductor devices such as thyristors derives its energization solely from the voltage across the array. A unidirectional current is developed to respond to that voltage and this current is utilized to develop an electrical charge of not more than a predetermined magnitude. The unidirectional current is also utilized to develop a signal which is proportional to the voltage across the array. When this signal reaches a predetermined level, indicative of an overvoltage condition of the array, a switching current is rendered operative to cause the stored charge to be applied to the gating electrodes of the array semiconductor devices to thereby render each such device conductive.