Abstract: A motor control method for determining the temperature of a motor wherein the operation and nonoperation times of the motor are monitored, an estimated temperature is determined as a function of the monitored times and predetermined temperature rise and temperature fall characteristics of the motor, and the motor is stopped and/or an alaram signal is generated if the estimated temperature exceeds a predetermined temperature.

Abstract: A motor driver interface (MDI) circuit includes fault detection apparatus effective to detect short circuits to the power supply in the switching transistors of an H-bridge reversible DC motor arrangement. A pair of timers distinguishes a true fault condition. The first timer is responsive to a continuous fault detection to define a first time period from its initiation; and a second timer is responsive to a continuous presence of a transistor conduction signal to define a second time period from its initiation. The apparatus stores a fault signal in response to the detection of the fault condition at the end of the first or second time periods with the first timer providing fault detection upon turn-on after the brief initial high transistor turn-on current and the second timer providing noise immunity.

Abstract: A protective time delay delay circuit delays energization to an electric load until a predetermined time has elapsed from a previous deenergization. A transistor has its emitter connected to an ac conductor and has its base coupled to an RC timing circuit. The collector is connected to the gate of a triac whose current electrodes are coupled to the thermostat conductor and to a load device. A small resistor and a zener can be connected to the transistor to provide brownout protection. A temperature sensitive resistor can be included to increase or decrease the lockout period as a function of temperature. This resistor can be remotely mounted in thermal proximity to the load to be protected. A thermistor placed in parallel to latching capacitor can provide thermal overload protection.

Abstract: The present invention comprises a relay control circuit that provides highly efficient and reliable control for devices that perform in demanding applications such as space. Multiple levels of redundant function control are provided by redundant actuators that perform mechanical operations. Each actuator is driven by redundant motors for increased reliability. Motor current sensing is provided to determine arrival of the actuator at mechanical stops, which are located at the full deploy position. Limit switches also sense when the actuators are in the full deploy position. In addition, multiple control signal so are required to initiate certain critical operations. Critical operations also are performed redundantly for increased reliability.

Abstract: A method and apparatus prevents the overheating of a line feed motor used in a printer. First and second timers are respectively provided to measure first and second time intervals. The second time interval includes a cessation period in which the line feed motor is not driven to allow for heat dissipation of the line feed motor. At the end of the first time interval, a determination is made as to whether the number of line feed pulses during the first time interval exceeds a predetermined limit. If the number of line feed pulses does not exceed the predetermined limit, the first time is reactivated. If the number of line feed pulses does exceed the predetermined limit, then the second timer is activated to allow for heat dissipation of the line feed motor.

Abstract: A compressed air supply system including an electric motor for driving an air compressor. An air reservoir connected to an outlet of the air compressor via a cooler. A dryer and a check valve, a pressure sensor coupled to the air reservoir for sensing the pressure therein. An unloading valve coupled to the outlet of the air compressor. A control circuit coupled to the electric motor and the unloading valve. A protective circuit coupled to the control circuit and the unloading valve for preventing the motor from starting under an overload condition and for averting the unnecessary running of the motor and driving of the air compressor.

Abstract: A technique for detecting the occurrence of stall currents in a D.C. motor control circuit and inhibiting the application of drive currents to the motor by monitoring the current flow through the motor and responding to stall currents that are continuous for a predetermined period of time.

Abstract: A protection circuit for stalling protection in commutatorless direct current motors is driven by Hall generators, in particular Hall IC's. A respective semiconductor circuit element (5, 14) disposed in series with each stator winding (1, 2) is turned on or off in dependence on a control voltage induced in the stator windings (1, 2). The control voltage (U.sub.B) is constituted by the sum of the operating voltage in the unenergized windings (1, 2) and the counter-e.m.f. induced in these windings, whereby, if the sum of these voltages is greater than the operating voltage, the semiconductor circuit element (5, 14) connected to the respective energized winding (1, 2) is turned on, and, if the counter-e.m.f. is zero or falls below a predetermined cut-off value, the respective semiconductor circuit element (5, 14) is turned off.

Abstract: An electrical short-circuit monitoring arrangement for a three-phase motor, including its supply lines, whose speed is controlled by a constant-current d.c.-link converter. The harmonic ripple voltage superimposed on the motor voltage generated as a consequence of the commutation by the constant-current d.c.-link converter at the output of the converter is determined, filtered, and supplied to a phase-monitoring unit, which when dropping below a selected amplitude variable of the harmonic voltage of at least one phase, triggers the switching module whose switching mechanism activates a disconnect switch to interrupt the motor circuit upon occurrence of a switchoff signal.

Abstract: A control transistor (3) is connected between a power supply terminal (1) and an output terminal (19). The base bias of the control transistor (3) is controlled by bias control transistors (12, 13), thereby the output voltage is maintained at a constant value. An overcurrent state is detected by a current control detecting transistor (22), and the base bias of the control transistor (3) is controlled by the bias control transistors (12, 13), so as to prevent the overcurrent. The current control detecting transistor (22) further detects the time when the potential of the output terminal (19) becomes approximately 0 V by, e.g., short-circuiting of a load, so as to control the base bias of the control transistor (3) through the bias control transistors (12, 13), thereby the current to the load is decreased to a value considerably smaller than a limited value for preventing the overcurrent.

Abstract: A circuit for driving a power transistor that forms a part of an inverter circuit used in motor control in which the circuit is switched at high voltages. The motor drive circuit isolates and amplifies a control signal so as to operate the power switching transistors. The base drive circuit employs two characteristics of power transistors to derive maximum protection and maximum performance simultaneously. This control is accomplished by sensing both the collector-to-emitter voltage of the power transistor as well as the base-to-emitter voltage thereof. In an alternate embodiment described herein, a feedback circuit is also provided sensitive to collector-to-emitter voltage for shortening the try-time associated with the power transistor.

Abstract: A protective circuit for an electric motor comprises a frequency signal generating circuit for generating a frequency signal in accordance with the rotational speed of the motor, a switching circuit switched over to either permit or cut off supply of current to the motor, and a detecting circuit for detecting that the period of the generated frequency signal has become larger than a predetermined period due to a decrease in the rotational speed of the motor, and cutting off the supply of current to the motor by the switching circuit.

Abstract: A motor control circuit for submersible pumps has features to prevent restarting while the electric motor is backspinning. The circuit includes a sensor for sensing the voltage produced by the residual magnetism in the rotor of the motor while it backspins. The voltage sensed is amplified, then rectified and compared with a reference voltage that is preset. The reference voltage corresponds to a voltage produced during backspinning at a selected maximum amount tolerable when restarting. The DC pulses are filtered to provide a corresponding voltage, then compared to the reference voltage. The control circuit is disabled from allowing a restart, either manual or automatic, when the corresponding voltage is greater than the reference voltage.

Abstract: A valve position monitoring and control system incorporates a proximity sensor positioned near a movable valve element to detect the operational position of the valve and includes circuit means coupled to a valve actuating solenoid for deactivating the solenoid in the event the valve fails to respond to command signals for positioning the valve in a predetermined position. In one embodiment, the system incorporates a pair of series connected valves used in presses which valves in turn are operated by solenoid actuated pilot valves. In the event either one of the valves do not operate either by opening within a predetermined time after actuation or closing within a predetermined time after their deactuation, the system of the present invention will not permit further operation of the valves until the system has been manually reset.

Abstract: A method of and a protection relay for protecting electrical equipment. The method includes dividing a predetermined dividend value by a signal corresponding to the load current in the equipment to provide a quotient signal, and then linearly integrating the quotient signal. When the integrated signal reaches a predetermined value, the equipment is tripped. This provides an overload vs tripping time characteristic which is substantially linear. The method further provides for sensing whether the equipment is operating in a start up mode or in a normal running mode, and then automatically to select a less sensitive overload vs tripping time characteristic when the equipment operates in the start up mode and automatically to switch to a more sensitive characteristic when the equipment reverts to its normal running mode.

Abstract: An overload-protection circuit for an electric motor has a current transformer whose primary winding is connected in series with the windings of the motor to be protected while two secondary windings are provided. The first secondary winding is connected to an actual-value current-monitoring circuit while the second secondary winding forms part of a voltage-supply network for the circuit. The primary winding is subdivided into a plurality of winding sections having respective taps for different nominal values of the overload current. The product of the number of turns of each winding section and the nominal-current value of the respective tap (ampere-turns) is the same for each winding and the respective tap.

Abstract: A circuit for preventing the energization of the starter motor for an internal combustion engine while the engine is running. A first SCR energizes the starter relay, and also a second SCR. Circuitry is provided to maintain the second SCR energized as long as the engine is running and to prevent the first SCR from being reenergized as long as the second SCR is energized. According to one aspect of the invention time delay means is provided to insure that all rotating parts can come to a stop before the starter motor can be reenergized.

Abstract: Disclosed is a magnetic circuit breaker having improved delay characteristics and particularly improved pulse tolerance. The trip coil of the breaker is spaced from the magnetic pole piece of a delay tube by a non-conductive, non-magnetic gap and the delay core is elongated. An inertia wheel is mechanically coupled to the trip armature to further increase pulse tolerance so as to reduce nuisance tripping in the presence of high but very short term overcurrents. The circuit breaker provides a significantly improved motor protection characteristic.

Abstract: Energization of a motor is controlled by a latching relay operated by switch means passing current from a capacitor to the winding of the relay. The capacitor is charged through a relatively large impedance unipolarity input.

Abstract: Complete protection of a three-phase submersible pump motor, such as the type used downhole in an oil well, is obtained with a solid state digital logic control system that monitors each of the three phase currents and shuts the pump motor down if any of those phase currents indicates either an underload or overload condition. Time delays are introduced before shutdown to avoid undesired nuisance shutdowns otherwise caused by transient or momentary conditions. When the pump motor is de-energized in response to an underload condition, it is automatically restarted after a predetermined time delay. All of the delay functions are precisely determined by division of the power line frequency. Downhole pressure and temperature are also sensed and if they become excessive the motor is automatically de-energized to prevent overheating. The presence of an auxiliary physical condition, such as filling up a retaining tank, also causes the pump motor to be turned off.

Abstract: A fault detector circuit in a silicon controlled rectifier (SCR) control for series-connected direct-current motors in which current to the motor flows in pulses through a main SCR as the main SCR is repeatedly turned on and off. If during operation the main SCR shorts, the field winding is disconnected from the armature and maintained disconnected. If during operation the main SCR is not defective but fails to commutate, the field winding is disconnected from the armature and then reconnected thereto. If the main SCR again fails to commutate, the field winding is again disconnected from the armature and is maintained disconnected therefrom.