Abstract: A safety device for preventing the automatic restart of a motor upon restoration of power to the motor. This device, in its preferred embodiment, includes a thyristor switch, such as a triac, in one of the power leads to the motor which is triggered by energizaton of the motor. Upon deenergizaton of the motor, the thyristor switch switches to its non-conductive state thereby preventing automatic restarting of the motor upon restoration of the power. A selectively actuable, momentary run switch is provided to momentarily shunt out the thyristor switch so as to selectively permit the restart of the motor.

Abstract: A motor speed control circuit includes a resistor, a voltage reference circuit, a first voltage comparator, a current mirror circuit for deriving first and second output currents according to the output of the first voltage comparator, and a motor. A voltage consisting of the sum of a reference voltage and a voltage generated across the resistor by the first output current of the current mirror circuit is applied to the first input terminal of the first voltage comparator. The second output current of the current mirror circuit is fed to the motor and to the second input terminal of the first voltage comparator. A second comparator detects the voltage difference between the first and second input terminals of the first voltage comparator. The output of the second comparator is applied to the current mirror circuit to enhance the starting torque of the motor.

Abstract: An electric nutrunner for tightening bolt joints to a desired tightening torque. The nutrunner utilizes a motor having a low moment of inertia and a control device that supplies a pulse to the motor as an indication that the nut-tightening is to be terminated, thereby braking the motor electrically.

Abstract: A controlled switch 4 provides current pulses derived from a battery 3 to a motor 1, having a series field 2 under command of a control unit 8 which provides command pulses for repetitive closing of the controlled switch 4. Current through the motor is sensed by a sensing resistor 6 and connected to a safety circuit 9 which, upon sensing of current flow in the absence of a control pulse from the unit 8, disconnects current to the motor by opening a controlled switch 5. To distinguish between (a) current flowing from the battery 3 l and (b) circulating current flowing during pulse gaps in a free-wheeling diode 7 connected across the field and armature of the motor, voltage across the free-wheeling 7 is sensed, thereby effectively sensing the conduction state of the free-wheeling diode and, if the free-wheeling diode is conductive, disabling the safety circuit to prevent spurious operation thereof during flow of inductive, circulating current through the bypass or free-wheeling diode under normal operation.

Abstract: The disclosed Leonard type elevator system comprises a reversible converter for controllably driving a DC motor, and an AC voltage detector and a DC voltage detector connected to the AC and DC sides of the converter respectively for detecting the voltages developed on the respective sides of the converter. When a difference in detected voltage between the two detectors exceeds a predetermined magnitude due to a decrease in the AC source voltage, a comparator produces an output serving to disconnect the DC motor from the converter. Also the comparator may produce such an output when the converter receives regenerative power from the DC motor.

Abstract: A static convertor with DC terminals for connection to a load object with a variable electromotive force includes a control arrangement for controlling the direct voltage of the convertor between maximum and minimum values, an arrangement for controlling the minimum value being connected to and dependent on the output of a sensing device which senses a quantity corresponding to the e.m.f. of the load object. The minimum value is limited to an upper value at which the commutation ability of the convertor is at least as great as the expected maximum direct current.

Abstract: A motor control means for power driven window including an reversible D.C. motor having first and second brushes and a third grounded brush. The motor control means also has a first switch for selectively supplying a D.C. power to one of the first and second brush to drive the motor. A solenoid is provided to be energized by a counter electromotive voltage induced between the first and second brushes during rotation of the motor. When the solenoid is energized, the solenoid acts to hold a second switch in a closed condition so as to maintain supply of the driving power to the motor.

Abstract: Disclosed herein is a direct current motor control comprising a direct current motor, a solenoid switch including an actuating coil, a first lead connecting the drive motor and the solenoid switch in series relation to each other, a second lead connected to the motor and adapted to be connected to one terminal of a direct current source, a third lead connected to the solenoid switch and adapted to be connected to the other terminal of the direct current source, a sub-circuit assembly including the solenoid actuating coil and a solenoid coil actuating switch connected in series with each other, a fourth lead connected to the sub-circuit assembly and adapted to be connected to the one terminal of the direct current source, a solenoid latching switch connected to the sub-circuit assembly in series relation thereto and also connected to the third lead, a fourth lead connected to the sub-circuit assembly in series relation thereto and in parallel relation to the solenoid latching switch and also connected to the f

Abstract: A method and apparatus for connecting a rotary drum drive, particularly a rotary drum drive of a rotary furnace or kiln, after disconnection for a short time, and before standstill of the oscillating drum, features detecting the movement of the oscillating drum and connecting the drive motor at a turning point of the oscillation or upon agreement with the direction of movement and the driving direction.

Abstract: A method of controlling the operation of a d.c. motor of a washing machine by energizing or de-energizing a reference voltage generator. The back-e.m.f. of the motor is compared with the reference voltage. The a.c. supply of the generator is controlled by contacts of detectors for the operating conditions of the machine, such as temperature of the suds or of electronic components, unbalance, opening of the door etc.

Abstract: To reduce noise and idling speed of electric motors, particularly series motors, the speed-torque characteristic of the motor is dropped with respect to the loaded speed-torque characteristic, by sensing no-load operation of the motor and deriving a sensed signal, the sensed signal being applied to controlled switches to abruptly change the effective voltage applied to the motor between values corresponding to the no-load speed-torque characteristic, or the load speed-torque characteristic and resulting in the desired speed, in dependence on the value of the sensed signal. Preferably, the operating condition of the motor is sensed by an inductive transducer, and a speed change is obtained by phase control, or half-wave rectification.