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: 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: 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 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: 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.

Abstract: The effect of commutation notches 35 appearing in the nominally sinusoidal alternating current (AC) line-to-line voltage, for example, v.sub.ab used to synchronize the firing of thyristors in three phase, phase-locked power converters 12 and 14 is essentially eliminated by reconstructing the corrupted line-to-line voltage by summing the integral of the corrupted line-to-line voltage .PSI..sub.ab with a signal proportional to the product of the delta load current, for example, i.sub.ab and the commutation inductance L.sub.c. The composite waveform .PSI..sub.ab +i.sub.ab .times.L.sub.c) resulting from the summation has well defined zero crossings 41 from which synchronizing pulses are generated for synchronizing the phase-locked thyristor firing circuit 18 implemented by either software or hardware techniques. Additionally, the reconstructed waveform is used to control commutation, particularly in the control of a load side converter i.e. inverter 14 which is utilized in an AC motor drive system.

Abstract: A saturable reactor snubber to improve the recovery characteristics of a clamp diode used in a power switching circuit is provided with a secondary winding to permit saturating the reactor via a secondary current pulse in order to improve the turn-on speed of the clamp diode. The current pulse for saturating the reactor at turn-on is preferably derived from a shunt snubber charging pulse or from an external generator synchronized to the turn-off time of a power switching device in the switching circuit.

Abstract: A system and method are disclosed for automatically machining a work piece to precise selectively determined dimensions under computer numerical control. A movable probe is calibrated against position reference surfaces and is then used to calibrate the position of a fixed probe. The latter serves as a position reference for calibrating the cutting edge of one or more cutting tools. All calibrations are performed under closed loop control. Appropriate tool position offsets are automatically determined from deviations between the programmed and the actual probe and tool positions and are entered into numerical control means to modify the programmed machining operation. After machining has been initiated, probing of the work piece occurs at least once before the final cut is taken and the appropriate tool position offsets are determined and entered to assure that the dimensions of the finished surface will conform to the desired selectively determined dimensions.

Abstract: A power control system for a DC electric motor includes a control power regulating means which selectively connects either the armature of the motor, the field winding of the motor or both in a series current path with a DC power source permits operation of the motor in either an armature current or field current control mode using a single regulating circuit. In the field current control mode a contactor connects the armature of the motor directly across the power source and the regulating circuit controls the field current to regulate torque developed by the motor. The armature circuit and field circuit are interconnected by a diode which permits electronic switching between armature current control and field current control modes of operation.

Abstract: A motor control system including sequencing circuitry for governing the mode of operation of an electric motor in accordance with feedback signals representing selected motor operating parameters further includes modifying circuitry to selectively effect a change in the mode of motor operation in response to an external signal.

Abstract: A gas turbine, copper-based alloy part having a crystalline structure in which grain boundaries are elongated in the direction of principal stress applied to the part when in turbine service exhibits especially enhanced strength and fatigue resistance in such direction. The part is prepared in a process in which it is first cast to shape in a mold and then directionally solidified by substantially limiting the heat flow from the part to a direction parallel to the principal stress direction.

Abstract: An electromagnetically operated, straight-line motion dual-break electrical contactor has current conductors entering a contact area from opposite directions. In the contact area the conductors are closely spaced and have finite parallel substantially flat portions with an insulative divider to prevent conductor to conductor arcing. A pivotable contact carrying bridge spans the conductors. The pivotable bridge compensates for contact wear or displacement. Screens are arranged in arc blow paths to aid in extinguishing arcs. The contactor arrangement and spacing controls the direction and enhances the magnitude of arc blow.

Abstract: A control system for a steam turbine operated with a steam bypass system. In the control system, bypass valve control is according to setpoints generated as a function of a combined flow reference (CFR) signal. The CFR signal is representative of boiler outlet flow under all turbine operating phases and is generated by multiplying the sum of the steam admission control valve flow demand and the high pressure bypass flow demand by boiler pressure. An actual load demand (ALD) signal indicative of the turbine demand for steam is produced from the product of the steam admission control valve flow demand and boiler pressure, and is used for intercept valve control. Excessive steam flow in the lower pressure bypass subsystem is prevented by providing an override for the normal control to prevent high heat impact to the condenser and latter stages of the turbine high pressure section.

Abstract: A solution to the problem of excessive rotation loss heating in a bypass steam turbine has been provided by the introduction of a reverse flow of steam to the high-pressure section of the turbine during those operating periods in which such heating is of concern. The present invention is directed to a control system for automatically selecting either the forward or reverse steam flow regime as is most appropriate, depending on turbine and other related operating conditions. In a preferred embodiment, the control system includes means for selecting either a forward or reverse flow control signal to govern the steam admission control valves; means for controlling the reverse flow valve and having decisional logic for determining whether the reverse flow valve shall be open or closed; and means for controlling the ventilator valve and having decisional logic for determining whether the ventilator valve shall be open or closed.