Abstract: The invention relates to a device for controlling a mechanism driven by at least one electric motor (11, 12), said device comprising a circuit (20, 38) for detecting the power consumption of the mechanism and for comparing the detected value with at least one current threshold, with confirmation during a defined time and a circuit (54) for controlling the stopping of the mechanism for a given time, as a function of the result of said comparison.Application more particularly to the field of high-capacity or wide-body aircraft, for the generation of pressure in their hydraulic circuits.

Abstract: A method and apparatus is disclosed or determining the remanent noise in a magnetic medium by DC saturation of a region thereof and measurement of the remaining DC magnetization. Conventional recording transducers may be used to determine the remanent noise. Upon determination, the remanent noise may then be compensated for in either or both of the record and playback modes for all varieties of magnetic media including, videotapes, cassette tapes, etc.

Abstract: A brushless motor lock detection apparatus for detecting a locked condition of a rotor of a brushless motor includes a pulse generator for generating pulses synchronized to the rotation of the rotor, a capacitor for charging a current during motor being locked, a control circuit for monitoring the charge in the capacitor, and a flip-flop circuit. The control circuit produces a lock detection signal when the charge in the capacitor reaches a predetermined level, and cuts off power to the motor. After a while, the control circuit starts to supply power to the motor. The flip-flop circuit produces a locked state signal which starts in response to the lock detection signal and ends in response to the pulse.

Abstract: A device and apparatus for monitoring faults in a three phase induction machine are disclosed herein. The device and method utilize values of the currents in the three phases and the voltages of the three phases to estimate a current portion which is not substantially affected by the load torque effects of the machine. This current portion is related to the unacceptable magnetic fields present in the machine. These fields are typically caused by electrical or mechanical problems in the machine, and when the current portion exceeds a predetermined limit, operation of the machine can be discontinued.

Abstract: There is disclosed a device for detecting an abnormality in relays which is adapted such that if there is a current flow through a motor (M) when first and second transistors (Q1, Q2) are off resulting from an abnormality such as melting of first and second motor driving relays (RL1, RL2), a controller (1) turns on the transistors (Q1, Q2) of a motor driving portion (2) in response to a detection signal from a signal detecting portion (3) and accordingly provides the same potential across the motor (M) to stop the motor (M) without a conventionally complicated, costly construction.

Abstract: An electronic protection device for providing thermal protection of a load by cutting off the multiphase supply of power to the load includes a thermal sensor having at least one resistive element thermally coupled to a temperature sensor connected to an electronic processor circuit. This circuit generates a command instruction in response to any overload detected by the temperature sensor. Each resistive element of the thermal sensor is fed with current by a current sensor on a phase wire supplying power to the load.

Abstract: An apparatus for thermal protection of an electric motor is provided, including a monitoring device for generating a signal representative of the current in a conductor supplying electrical power to the electric motor. A control circuit processes the current signal and utilizes the processed signal and motor thermal parameters, including the thermal resistance and thermal capacitance of the rotor, to generate signals representative of the temperature of at least the rotor. A comparator circuit, which may be part of the control circuit, compares the temperature signals to reference maximum temperature signals and produces a control signal when the temperature signals and reference signals satisfy a predetermined relationship. The control signal may be applied to a contactor to interrupt current to the motor. A method for thermal protection of an electric motor is also provided, including thermal modeling of the rotor temperature.

Abstract: A current throttle resistor external to a contactor device protects an electrical power distribution circuit coupling a load to a power line. The contactor has electrical switching contacts in series with the load and the line, and for example, an electromagnetically controllable switch for opening the contacts. A current sensor is coupled to the controllable switch for opening of the contacts upon occurrence of a high current fault in the power distribution circuit exceeding a predetermined threshold. A resistive element in series with the power distribution circuit between the line and the load, provides a voltage drop for limiting current during the high current fault. The resistive element can be a nichrome strip or similar positive temperature coefficient resistance having a low cool resistance, and is thermally isolated from the controllable switch by mounting in a resistor housing external to the contactor.

Abstract: In a method and device for monitoring the operation of a motor, the current drawn by the motor is sensed a preselected time after a peak of current is sensed. This sensed current is then compared to both a minimum and a maximum current threshold value to determine whether the sensed current is inside or outside the range of currents defined by the minimum and maximum current threshold values. The minimum and/or maximum current threshold values are dynamically adjusted as a function of the comparison.

Abstract: In a multiple contactor installation where each contactor provides overcurrent protection, overload information in passed from one active contactor to the next as a percentage of the trip level of the respective contactors.

Abstract: A washing machine includes a brushless motor, a position sensing element for sensing a rotational position of a rotor of the motor, a motor drive control circuit composed of an inverter main circuit for driving the motor and an inverter control circuit for controlling the inverter main circuit based on a signal generated by the position sensing element, a current detector for detecting a current flowing in the inverter main circuit, an overcurrent determining circuit generating an overcurrent detection signal when the current detected by the current detector exceeds a reference value, and an abnormal condition detector for generating an abnormal condition detection signal when the number of times of output of the overcurrent detection signal generated by the overcurrent determining circuit reaches a predetermined value.

Abstract: Disclosed is a negative-sequence time-overcurrent relay for use in a polyphase synchronous rotary electric machine having a main-circuit breaker and an exciting circuit.

Abstract: A controller apparatus for an electric vehicle includes a power supply, a power converting section for converting power supplied from the power supply, a motor which receives an output from the power converting section to drive the electric vehicle; an accelerator opening detector for detecting an accelerator opening; a controller section for controlling said power converting section in response to a detected output from said accelerator opening detector; a current detector for detecting the current supplied to the motor from the power supply; and failure decider for deciding that the controller suffers a failure when the output from the current detector is not smaller than the reference value previously determined in accordance with the accelerator opening, thereby stopping the drive of the motor. In such a structure, the torque not smaller than that required by a driver is produced so that it is possible to prevent the electric vehicle from running away.

Abstract: A washing machine includes a brushless motor, a position sensing element for sensing a rotational position of a rotor of the motor, a motor drive control circuit composed of an inverter main circuit for driving the motor and an inverter control circuit for controlling the inverter main circuit based on a signal generated by the position sensing element, a current detector for detecting a current flowing in the inverter main circuit, an overcurrent determining circuit generating an overcurrent detection signal when the current detected by the current detector exceeds a reference value, and an abnormal condition detector for generating an abnormal condition detection signal when the number of times of output of the overcurrent detection signal generated by the overcurrent determining circuit reaches a predetermined value.

Abstract: A sensor circuit for monitoring the operation of a fan in an electronic device includes a current sensor that produces a voltage signal proportional to the magnitude of the current flowing through the fan. The proportional voltage signal is filtered to extract an rms dc signal that then is compared with a minimum and maximum voltage threshold in two voltage comparators. If the voltage of the filtered signal exceeds the maximum threshold value, or is less than the minimum threshold value, a fan failure signal is generated and transmitted to an external monitoring unit. The sensor circuit can be implemented with a standard two-wire fan and interface connector.

Abstract: A motor control unit for protecting a motor against overload, short circuit and ground fault currents. The unit monitors the currents in each phase of the motor to provide values representative of each phase current. The unit also includes a contactor for opening and closing each phase, wherein the unit controls the contactor based upon the values representative of the phase currents. The contactor is opened where the phase currents exceed limits which indicate that either an overload, short circuit or ground fault situation exists at the motor. A magnetic trip circuit breaker can also be provided to operate in cooperation with the unit to provide instantaneous trip protection for current levels which are relatively high in relation to those for which the contactor is rated.

Abstract: An electrical overcurrent circuit provides both digital based modeling and analog based modeling of the temperature of an electrical conductor to simulate the conductor temperature during all expected operating conditions including a condition when electrical power is unavailable to the electrical overcurrent circuitry. When electrical power is available to the circuitry, the conductor temperature is calculated from the sensed load currents to form the digital based model. During such a condition, the analog based model is forced to track the digital based model. Once the temperature of the electrical conductor exceeds its maximum safe operating temperature, the electrical overcurrent circuitry initiates a trip of the circuit breaker. Since the overcurrent circuitry is powered either by the sensed load currents or derived from the circuit breaker output, the circuit breaker trip will result in a loss of electrical power to the electrical overcurrent circuitry.

Abstract: A self-diagnosing apparatus for a brushless motor which has a voltage detection circuit for detecting drive current to the brushless motor, and for outputting voltage at one of different levels corresponding to a short circuit condition, an open circuit condition and other conditions. When the output of the voltage detection circuit is at a high (H) level, a short circuit condition is determined, whereas when that output is at a low (L) level, an open circuit condition is determined. When the output of the voltage detection circuit is at a level intermediate between "H" and "L" levels, and simultaneously when the output voltage does not pulsate, a motor lock condition is determined.

Abstract: The pulse width modulated DC motor speed control circuit indirectly senses motor current using sense MOSFETs and a peak detector circuit with storage capacitor for deriving an average motor current signal. The average motor current signal is used both in the feedback loop of the pulse width modulated speed control circuit and also in the motor shutoff or clutch circuit. The clutch circuit shuts off power to the motor when a user-settable torque is reached. The motor speed control circuit is therefore adapted for use in hand-held DC power tools such as screwdrivers and nutdrivers which stop rotation at a predefined torque.

Abstract: An actuator in which an output shaft can be made to stop by a simple structure and in which actuator assured restart of the output shaft can be performed. The actuator comprises a motor, an output shaft provided with an external threading, and a connecting member having an internal threading engaged with the external threading of the output shaft. The actuator further comprises a resilient member for applying a predetermined load to the output shaft when the output shaft reaches the end of its moving range. The connecting member may comprise an internal screw member having a first protrusion formed on an outer surface thereof and a gear member having a second protrusion. When the second protrusion impacts with the first protrusion, a large starting torque is obtained. Further, two PTC thermistors are provided in a protection circuit, each thermistor allows flow of a current in only one direction, so as to prevent a reduction of a starting current.

Abstract: A motor control unit for protecting a motor against ground fault currents. The unit monitors the currents in each phase of the motor to provide values representative of each phase current. The unit also includes a contactor for opening and closing each phase, wherein the unit controls the contactor based upon the values representative of the phase currents. The contactor is opened when a ground fault situation exists at the motor.

Abstract: Free wheeling diodes are protected against an overcurrent. When counter electromotive forces E.sub.VU and E.sub.WU established in a tri-phase motor cause regenerative currents I.sub.V1 and I.sub.W1 to flow to transistors Q4 and Q6, and to a protection diode D2, it is decided that the protection diode D2 is in overcurrent state. In response to the decision, the transistors Q4 and Q6 are turned off, which allows that regenerative currents I.sub.V2 and I.sub.W2 flow in protection diodes D3 and D5 because of the counter electromotive forces E.sub.VU and E.sub.WU. The energies of the regenerative currents I.sub.V2 and I.sub.W2 are regenerated at a capacitor C. Thus, since a regenerative current which once passed by only one protection diode is divided into two current flows into two protection diodes, the overcurrent state is terminated.

Abstract: Disclosed is a ground fault detection apparatus for an operating, normally ungrounded supply system, the apparatus having a periodically grounded center tap of a test impedance that is connected across conductors of the system, and detector circuitry including a charge balance circuit having low gain and wide dynamic range that measures the amplified voltage output of a Hall effect current sensor. A preferred implementation of the circuit has a charge transfer variable oscillator. A pair of microprocessor-controlled counters that are responsive to the oscillator precisely measure the average frequency of the oscillator over intervals that are automatically maintained at approximately one second in duration, the microprocessor calculating the fault current as the difference between current measurements taken with and without the center tap grounded.

Abstract: A device for motor and short-circuit protection in low-voltage plants includes a contact device (3) which is connected in series with a tripping circuit comprising two parallel-connected current branches. One of the branches comprises a first thermistor (1) serving as an overload protective means and connected in series with a second thermistor (2) serving as a short-circuit protective means. The second branch comprises a multi-turn excitation coil (4) which is adapted to influence the contact device (3) for opening thereof at an overcurrent. The resistivity of the two thermistors (1, 2) has a positive temperature coefficient in the temperature range in question. The first thermistor (1) may consist of a ceramic material or electrically conductive polymer composite. The second thermistor (2) consists of polymer composite with a extremely high content of electrically conductive filler and is, in addition, layered.

Abstract: In a preferred embodiment, a high-frequency, pulse-width-modulated, power-transistor, DC motor speed controller having current limiting in both drive and regenerative modes, essentially constant ramping rates regardless of whether or not the operator switches to neutral before changing direction, a simple sequencer which controls the timing of four functions--both drive and regenerative current measuring circuits and both drive and regenerative transistors, a highly effective transistor filter capacitor arrangement, and circuitry in which the level of regenerative current is used as an input to control the current under which the direction relays switch.

Abstract: Flashover protection is provided for a locomotive propulsion system including a plurality of d-c traction motors each having a commutator subject to flashovers, a traction alternator having armature and field windings and a rotor driven by a prime mover, a controllable source of excitation current connected to the alternator field, and means including an electric power rectifier for connecting the alternator to the motor commutators. It comprises means for producing a fault signal whenever a flashover occurs in any motor, a solid-state controllable electric valve connected between the excitation current source and the alternator field and having alternative conducting and non-conducting states, and means for changing the valve from conducting to non-conducting states in response to a fault signal being produced, whereupon the magnitude of excitation current in the alternator field is rapidly reduced toward zero and the alternator's output current is correspondingly decreased whenever a flashover occurs.

Abstract: A power delivery circuit for supplying load current to a load includes a current switch connected on the high potential side of a load. In order to detect a current condition, such as an over-current condition in the load, a current sensing and detection circuit preferably cooperates with the current switch wherein such switch comprises a multicellular device with a plurality of terminals. Such terminals include a first main current terminal connected to a source of high potential, a second main current terminal connecting a majority of device cells to the load, a first auxiliary terminal connected at one end to a minority of device cells so as to provide a current generally proportional to the main device current, and a second auxiliary terminal connected at one end to a majority of device cells.

Abstract: A circuit is provided for detecting the deposition of an electromagnetic contactor which opens and closes a drive circuit connecting a power source to a load. A load current of the drive circuit and an operating current for operating the electromagnetic contactor are detected and applied to a detection circuit. The thus detected load current and operating current are used to determine the deposition of the electromagnetic contactor. Further, in the event of a detected malfunction in the electromagnetic contactors, a breaker of the drive circuit is automatically opened.

Abstract: An automatic controller for use with a motor. A switch interconnects the motor and a power source for selectively establing an electrical connection therebetween. A relay coil is connected to the motor. When the motor is connected to the power source via the switch, the relay coil latches the switch in a steady connecting state. When increased current overdraw of the motor is sensed, a current-limiting thermistor limits or interrupts the current flow across the relay coil, to set the switch to a disconnect state and to cause the motor to stop.

Abstract: In a power supply circuit for a motor in which a power source line can be opened and closed by a first opening-closing device, a construction is adopted which has a electrically controllable second opening-closing device connected in parallel to the first opening-closing device, a comparator for comparing the voltage of the motor load side with a predetermined value, a controller for controlling the opening and closing of the second opening-closing device on the basis of a signal from the comparator, and a current limiter device provided in parallel to the second opening-closing device, whereby a rush current when the first opening-closing device is closed can be suppressed to thereby prevent the fluctuation of the source voltage and the deterioration of the contacts of the first opening-closing device.

Abstract: An overload control circuit and method of operation for protecting a three-phase motor from damage due to overload includes monitors reading the load on each phase of the motor and circuitry for combining the three separate phase signals into a single combined load signal which triggers the overload circuit. The gain on the combined load signal and the overload trip delay time may be calibrated and monitored by an external meter to provide for accurate and inexpensive calibration to accommodate specific operating characteristics of the motor being monitored. The circuit provides visual readouts of the mode of operation, including: (1) operating mode; (2) overload onset; (3) shut down initiated; and (4) delay to restart.

Abstract: A winch having an electronic current limiter to shut off power to the drive motor when a load limit is attained. The electronic current limiter utilizes a linear hall effect transducer mounted in a torroid surrounding a conductor carrying current to the motor. The transducer outputs a voltage which is compared to a regulated preset voltage. The regulated preset voltage is preset at a value that corresponds to the voltage output of the transducer when the maximum allowed current is flowing in the current carrying conductor. The preset voltage establishes a trip point or threshold. The output voltage of the transducer and the preset voltage are compared and when the output voltage of the transducer crosses the threshold or trip point, power to the winch drive motor is shut off. The electronic current limiter includes a reset circuit that requires the motor to be driven in the reverse direction after an overload shut down before the motor may be run in the initial direction.

Abstract: A coil is connected to a voltage source by a switch enabled by a drive signal of fixed duration. Drive current in a coil is terminated by a chopper circuit if it reaches a predetermined peak level before the end of preselected rise time interval. The chopper circuit is inhibited from operation until the end of the rise time interval during which time the drive current is allowed to decay. The chopper circuit is enabled at the end of the rise time interval for chopping the drive current at an average peak current value for the duration of the preselected time. The total amount of energy supplied to the actuator is adjusted by allowing the current to decay if the peak current is reached before the end of the predetermined rise time interval and then by chopping the current at a predetermined switching rate for the duration of the preselected time of the drive signal. Short circuit protection is also provided during the predetermined rise time interval.

Abstract: A monitoring system for an electric motor including a temperature sensor (5) for monitoring the operating temperature of a motor, a memory (4) in which is stored the absolute maximum operating temperature and a predetermined maximum permitted operating temperature of the motor, and an indicator (6) for indicating the sensed temperature as lying: a) within a safe operating range, below the predetermined maximum permitted operating temperature; b) within a hazardous operating range, between the predetermined maximum permitted operating temperature and the absolute maximum operating temperature; and c) at or above a dangerous operating range, lying at or above the absolute maximum operating temperature. The monitoring system further includes a recorder (93) for recording the number of times the motor is operating beyond the predetermined maximum permitted operating temperature and the number of times the motor is operated beyond the absolute maximum operating temperature.

Abstract: Flashover protection is provided for a locomotive propulsion system including a plurality of d-c traction motors each having a commutator subject to flashovers, a traction alternator having armature and field windings and a rotor driven by a prime mover, a controllable source of excitation current connected to the alternator field, and means including an electric power rectifier for connecting the alternator to the motor commutators. It comprises means for producing a fault signal whenever a flashover occurs in any motor, a solid-state controllable electric valve connected between the excitation current source and the alternator field and having alternative conducting and non-conducting states, and means for changing the valve from conducting to non-conducting states in response to a fault signal being produced, whereupon the magnitude of excitation current in the alternator field is rapidly reduced toward zero and the alternator's output current is correspondingly decreased whenever a flashover occurs.

Abstract: A control system for an electric-motor-driven power tool, comprising solenoid operated switching contacts in a mains supply circuit for controlling the supply of mains current to the motor, a latching circuit for normally holding said switching contacts closed during normal operation, a stop switch for breaking the latching circuit to open said switching contacts when it is desired to stop the motor in normal operation, and a reed relay having switching contacts disposed in the latching circuit and a coil disposed in the mains supply circuit to the motor. The reed relay is arranged to break the latching circuit automatically, and thereby disable the motor, if the current supply to the motor exceeds a predetermined level. A movement detection device is adapted to trigger the latching circuit to open the solenoid operated switching contacts in the event of the control system being physically moved in operation.

Abstract: An electric motor controller comprises a circuit for selecting between driving and braking an electric motor in accordance with the health or otherwise of a pair of main electric motor control switches (14 and 16). In a preferred embodiment the health of the switch is determined by the voltage (A) between the switches. The controller also comprises apparatus for detecting the sense of movement of the motor. In the event that the motor is moving in a sense opposite to that selected, the apparatus increase field current to reduce the armature current thereby increasing the braking effect of the motor. Also in the controller are apparatus for changing from armature to field current control and vice versa, in response to a given magnitude of control signal. In order to provide an unambiguous change-over, a lockout circuit is provided to inhibit change-over in a transition region. The lockout circuit maintains the mode of control to above/beneath the change-over level when changing from one level to another.

Abstract: A torque coupling system includes an impeller that is connected to one end of an impeller shaft without the use of threads. The connection is made by cement and dowels. A drive system for the shaft includes a hollow coupling into which the other end of the shaft can be fitted. The shaft includes longitudinally extending slots formed at its end. The coupling includes spaced, longitudinally extending keys adapted to be fitted into the slots formed in the shaft. The drive system also includes a torque limiter that is conected intermediate the coupling and a drive motor. If the drive motor is an electric motor, the motor can be provided with automatic shut-down circuitry that is activated in the event of a current/torque overload. Visual and aural alarms are provided to alert the user that a shut-down has occurred.

Abstract: An apparatus for protecting the fault current intolerant elements of a motor starter circuit or the like is comprised of a protective shunt which bypasses the fault current intolerant elements in response to the detection of high fault currents. The protective shunt is formed of a "U" shaped conductor which flexes in response to the magnetic field created by the flow of the high fault currents through the "U" shaped conductor. Electrical contacts place on one leg of the "U" shaped conductor and on a stationary conductor form a shunting switch which conducts high fault currents around the starter circuitry. In a second embodiment, the stationary conductor is replaced with a flexible conductor which carries an armature. The magnetic armature is attracted by a focussed magnetic field from a magnetic yoke positioned around one leg of the "U" shaped conductor.

Abstract: An electrically driving system for the outer rearview mirror erects or folds the mirror body by the operation switch for rotating the incorporated motor normally or reversively. The system comprises a momentary operation switch, normal and reverse relays and limit switches for disconnecting self-holding circuits of the relays and motors from a power source independently of one another by detecting erected and folded states of the mirror. When the normal or reverse relay is rendered operative by the momentary operation switch, the incorporated motors are driven to cause rotation of a plurality of the mirrors. The mirrors are stopped independently with disconnection of motor circuit caused by the action of the limit switches when they reach to the erected or folded state.

Abstract: Protection apparatus for an AC or DC motor (4) and a static drive (8), including a static inverter or a static drive (8). An I.sup.2 T signal is modified to take account of the frequency with which the switching elements of the drive (8) are switching their load current (at 42) and other factors. The modified I.sup.2 T signal is lowpass filtered in a filter whose cutoff frequency is also a function of the drive's switching frequency. The resulting drive protection signal is compared with a predetermined threshold. An I.sup.2 T signal is also modified to take account of the speed of the motor and other factors, then filtered, to provide a motor-related signal (at 90). Upon occurrence of an overload both the drive-related signal and the motor-related signal are indpendently capable of turning off the system by tripping a line contactor (6).

Abstract: A motor protection apparatus with a current monitor, the current monitor sensing the presence of current in at least one phase of an electric motor. An ammeter is responsive to the monitor, the ammeter indicating the level of current present in the motor phase. A variable resistor is interposed the monitor and the ammeter, allowing the ammeter to selectively indicate start current and run current present within the motor phase. An optical isolator is responsive to the ammeter for indicating readings of the ammeter at predetermined values. A relay is responsive to the optical isolator, for controlling the presence or absence of input voltage to the motor. The motor protection device senses fault conditions in both the start mode and run mode of the motor, and initiates appropriate responses thereto. The motor is thereby protected from permanent damage by the early detection of fault conditions. The device operates on electric motors having one or more phases, including three phase motors, as well as D.C.

Abstract: A digital circuit interrupter includes a microprocessor programmed for tailored overcurrent protection to industrial power systems containing a plurality of electric motors as well as motor protective relays. A communication link permits the overcurrent set points to be selectively set within the microprocessor memory from a remote location. The tailored overcurrent motor trip parameters are then derived by means of a logarithmic interpolation algorithm which resides in the microprocessor memory.

Abstract: This invention concerns a circuit arrangement for current limiting for a.c. machines with phase gating control by solid-state devices, aimed at achieving a smooth start by arresting the steady decrease in the ignition angles upon the attainment of a predetermined limiting current value. For use with single-phase measurement of the load current, a circuit is provided for measuring the instantaneous value of the magnitude of the load current, such as a threshold-value detector, which is actuated by a single-phase full-wave rectified load current. The output of this threshold-value detector is applied to a monostable digital device.

Abstract: There is disclosed a direct current motor drive system comprising a direct current motor operable in a forward motoring mode receiving current from a power source and in a reverse inversion mode providing inversion current to the power source. The drive system includes a converter for controlling motor operation. The converter converts alternating current, received from the power source, to direct current. The converter supplies direct current across terminals of the motor when operating in the forward motoring mode. The system includes an inversion fault current limiter for limiting inversion fault currents associated with motor operation in the reverse inversion mode without effecting the supply of current to the motor in the forward motoring mode. The inversion fault current limiter is electrically connected in series between the converter and one armature terminal of the motor. The inversion fault limiter includes a diode switch connected in parallel with a resistor.

Abstract: An A.C. solid state power controller for controlling the current through a load from an alternating current source, including a diode bridge rectifier with its direct current output connected to a solid state switch, such as a MOSFET or a bipolar transistor, that is gate controlled by gate signals synchronized to the A.C. source. The gate signals are provided from an optocoupler to control the solid state switch and the load current. Overload, short circuit, and low A.C. line voltage conditions are sensed by protection circuits which signal the optocoupler to turn off the solid state switch and, thus, the load current. A fast turn off time, in the range of a few microseconds, is achieved which, together with the rectifier and solid state switch configuration, provides a power controller which is resistant to short circuit and overload destruction present in conventional A.C. solid state circuit breakers and power control devices.

Abstract: A hoist for raising and lowering objects with an apparatus for detecting mechanical overload of the hoist. The system provides a hoist having an alternating current motor connected to an alternating current power supply. The level of current of the power supplied to the motor is compared to a level of power indicative of a mechanical overload condition. If the current signal representative of the actual motor current level equals or exceeds the mechanical overload reference current then an overload output signal is provided.

Abstract: A multiphase electric machine having a failed electrical component detector includes a rotating member and a plurality of electrical components carried by the rotating member and arranged in groups for conducting electrical current. A plurality of detectors is carried by the rotating member with each of the detectors responsive to one of the groups of electrical components for detecting component failures. A plurality of light emitting diodes are carried by the rotating member so as to be grouped into concentric circles according to electrical phase. Each of the light emitting diodes is responsive to one of the detectors such that a component failure, and the phase in which that failure occurs, can be observed by the naked eye. A stationary monitor is disposed about the rotating member and is responsive to the plurality of light emitting diodes for providing an indication of the number of component failures per phase.

Abstract: A generator-motor apparatus with economical protection measures for use in a variable speed pumping-up electric power plant, having a main transformer, a secondary winding of which is coupled to an electric power system, a power system breaker connected to a primary winding of the main transformer, a syncronizing breaker connected in series with the power system breaker, a generator-motor, a rotor of which is mechanically coupled to the pump-turbine and an armature winding of which is connected to the power system through the synchronizing breaker, the power system breaker and the main transformer, and an excitation circuit, including a frequency converter for supplying a field winding of the generator-motor with AC voltage of the variable frequency and a converter transformer for feeding the converter, which is branched from a junction of the power system breaker and the synchronizing breaker.

Abstract: An electric motor controller comprises a circuit for selecting between driving and braking an electric motor in accordance with the health or otherwise of a pair of main electric motor control switches (14 and 16). In a preferred embodiment the health of the switch is determined by the voltage (A) between the switches. The controller also comprises apparatus for detecting the sense of movement of the motor. In the event that the motor is moving in a sense opposite to that selected, the apparatus increase field current to reduce the armature current thereby increasing the braking effect of the motor. Also in the controller are apparatus for changing from armature to field current control and vice versa, in response to a given magnitude of control signal. In order to provide an unambiguous change-over, a lockout circuit is provided to inhibit change-over in a transition region. The lockout circuit maintains the mode of control to above/beneath the change-over level when changing from one level to another.