Abstract: A circuit (10) for braking a polyphase dc motor (12) includes a circuit (38) for producing an output signal indicating that the motor has slowed at least to an actual rotational speed and a braking circuit (42-44, 26-28) to brake the motor (12) when the output signal indicates that the motor has slowed at least to an actual rotational speed. The circuit (38) for producing an output signal indicating that the motor (12) has slowed at least to an actual rotational speed includes a first counter (70) for counting pulses of a speed signal, which may be a standard tach signal. The first counter (70) produces a first output when the first counter (70) reaches a first predetermined pulse count. A second counter (72) counts clock pulses from a clock generator (48) to produce a second output when the second counter (72) reaches a second predetermined pulse count.

Abstract: An improved window covering and lighting system for a window in a room includes a plurality of cornices, each cornice including a window covering supported by the cornice and movable between an open position and a closed position, an actuator supported by the cornice for moving the window covering between the open position and the closed position, a lighting system mounted to the cornice, and a programmable logic unit for operating at least one of the actuator and the lighting system independently from one another upon demand. The system also includes a remote control unit providing a signal selectively to the programmable logic unit to operate at least one of the plurality of cornices. Each of the plurality of cornices further includes a light sensor for sensing ambient light conditions in the room, and a motion detector for detecting occupance of the room. The programmable logic control unit is responsive to the sensed ambient light conditions and the detected occupance.

Abstract: A control for operating an inverter coupled to a switched reluctance machine is responsive to the magnitudes of current flowing in the phase windings of the machines and controls switches in legs of the inverter based upon such magnitude.

Abstract: An energy efficient low-power integral electronically commutated fan motor and control circuit assembly mounted on a circuit board for use in refrigerators utilizing a Hall sensor to provide positional control signals for sequential energization of the windings with the Hall sensor energization being pulsed, and the motor stator windings energized only during a portion of the period, when rotational torque produced by the energization is greatest in order to reduce the power input to the assembly. Integrally molded multi-function components including the coil bobbin, ground pin, Hall sensor holder, motor bearing oil well covers, and assembly housing provide positioning, support, and securing assistance along with electrical and magnetic operative connections and positioning.

Abstract: An apparatus and method for precisely controlling a driven component in an electromechanical system, particularly for controlling the speed of a photoreceptor or intermediate transfer belt in an electrophotographic printing machine. A sensor monitors the speed of the driven belt and generates and sends a signal indicative thereof to a controller. A second sensor monitors the rotational speed of the drive motor for the component and also generates a signal indicative thereof and sends that signal to the controller. The controller processes the signals so that a preselected belt speed is maintained while minimizing or eliminating torque disturbances caused by the rapid fluctuation of the motor velocity without the necessity of using an inertial flywheel.

Abstract: A control device for controlling a plurality of motors of an air conditioner comprises a plurality of power circuits each for supplying a corresponding DC voltage to drive a respective motor. Motor driving circuits, each having a plurality of switches, supply the DC voltage from a corresponding power circuit as an AC voltage to windings of the corresponding motor. A rotational position of each corresponding motor is detected, and a position detecting signal is generated dependent thereon. Switch driving circuits, each receptive of a corresponding driving signal, drives the plurality of switches of each corresponding motor driving circuit. A single microcomputer controls the rotation of each of the plurality of motors by generating the plurality of driving signals.

Abstract: A method of controlling operation of a DC motor including the steps of detecting the level of acceleration caused by the rotation of the output shaft of the DC motor; determining the square root of the detected level of acceleration; and supplying the DC motor with a driving voltage which is determined in accordance with the difference between the square root of the acceleration and a voltage command.

Abstract: A frequency, voltage and waveshape converter is placed between the terminals of an ordinary single-phase power line and the power input terminals of a three-phase induction motor. The converter is operable to provide to the power input terminals of the induction motor a three-phase AC voltage of frequency, magnitude and/or waveshape controllably different from those of the power line voltage, thereby to permit effective control of motor speed and power factor. The frequency of the AC voltage is adjustable over the range of 12-120 Hz, with the effective magnitude of the AC voltage being automatically adjusted in proportion therewith, thereby providing for a very wide range of motor speed control without incurring reduced motor operating efficiency.

Abstract: A rotary induction machine having wound primary and secondary windings with capacitive means connected directly across said secondary windings and resistive means connected in series with said secondary windings.

Abstract: An electric tool including a variable speed switch assembly including a potentiometer having a central rotatable member defining a bore with a noncircular cross section and a molded plastic speed control wheel housing the potentiometer. The speed control wheel includes a central post with a cross section corresponding to the cross section of the central potentiometer bore such that the central post can be housed in the central bore in only one relative position with respect to the central rotatable member. The variable speed switch assembly also includes a switch cover having projections which snap into designated holes provided in a circuit board such that the switch cover and the circuit cannot be incorrectly assembled. The switch cover includes a stop member that extends into a semi-circular recess in the speed control wheel to provide mechanical stops so that rotational movement of the speed control wheel corresponds with the range of the potentiometer.

Abstract: A food processor is provided having a motor (18), a bowl (10) and a beater (12) which are movable relative to each other by a drive by the motor (18), a switching means (48) for switching the motor (18) on and off under the control of a start signal (START) and at least a first stop signal (STOP1) respectively, torsion measuring means (28/30, 32/34) for producing a torsion signal (TS) which is a measure for the torque necessary for the drive, a signal processing unit (42) for producing at least the first stop signal (STOP1) in response to the torsion signal (TS). The signal processing unit (42) includes a first differentiator (56) and/or a second differentiator (58) for producing the first (DTS) and the second derivative (DDTS) of the torsion signal (TS) and a comparator (62) in which the first (DTS) or second (DDTS) derivative is compared with a reference value (REF1). When the reference value is exceeded, the comparator produces a stop signal (STOP1) to switch off the motor (18).

Abstract: A multi-function hand-held power tool includes an electric motor for driving a tool holder and control means for energizing the motor in accordance with a selected combination of operating conditions under which the tool is to be used. Located on the housing of the tool is a keyboard for inputting to the control means information to define the selected combinations of conditions. The keyboard has a first single key for selecting a tool function, for example drilling, from a defined range of tool functions, a second single key from selecting a required workpiece material for example wood, from a defined range of workpiece materials, and two further keys for selecting, from a defined range, another parameter, for example drill size, appropriate to the selected tool function. A visual display also located on the tool housing is energizable to show symbols indicative of the selected combination of operating conditions.

Abstract: An atmospheric electrode is charged by electrostatic induction from a leader stroke which is associated with lightning formation. The electrode is earthed through a varistor which becomes conductive when the value of the tension associated to the electric field at ground exceeds a pre-determined value. In this way, a destructive return stroke, which usually follows a leader stroke during lightning formation, is avoided.

Abstract: Apparatus for the supervision of a sudden pressure relay (SPR) system which protects a power system network transformer having a plurality of windings associated with each phase of the power system network. This apparatus overcomes the difficulties associated with previous overcurrent supervision of the SPR system for multiple-winding transformers. The apparatus utilizes a maximum restraint signal selection network which offers a discriminating differentiation between high and low current levels in all of the transformer windings and accomplishes this in one embodiment with a single measuring unit per phase of the power system network. For each phase, when the selected maximum restraint signal exceeds a predetermined level, the supervisory unit blocks the SPR from operating the breakers which isolate the power transformer from the power system network. This blocking condition is relieved after a predetermined time period from when the selected restraint signal falls below the predetermined level.

Abstract: A protection circuit for preventing an over-current condition if the semiconductor power controller in an electric train power control circuit is defective. The power controller is connected in series through first and second switches to a D.C. power source. A capacitor is also connected to the power source through the two switches and through a charging resistor connected in parallel with the second switch. When the first switch is closed, the capacitor is charged through the first switch and the resistor. After the capacitor voltage reaches a set reference voltage during a predetermined time interval, the second switch is closed to permit the power control equipment subsequently to apply power to the driving motor of the train. If the capacitor voltage does not reach the reference voltage during the predetermined time interval, then the second switch remains open and the first switch is re-opened to completely disconnect the power control equipment from the D.C. power source.

Abstract: Motor control systems having solid-state components are commonly used on industrial vehicles such as lift trucks. Such solid-state components are easily damaged by excessive transient voltages. The subject invention includes a power supply for supplying direct current to a motor circuit, wherein the direct current has a nominal direct current voltage value and as associated transient voltage component. A pulse control circuit supplies current pulses from the power supply to a motor. A sensing device controllably produces a fault signal in response to the amplitude and frequency of occurrence of the transient voltage component exceeding a predetermined maximum value. An override circuit receives the fault signal and responsively modifies the current pulses delivered from the power supply to the associated motor.

Abstract: A protective circuit for a semiconductor laser supplied with an excitation current by a current generator circuit is created using a transducer, whose output is controlled by the laser light, a limit circuit cooperating with the transducer and a current shunt circuit energized by the limit circuit and switched in parallel with the semiconductor laser. Once the permissible emitted light power is reached, excessive excitation current is diverted to the shunt circuit. Exemplary embodiments of the invention are found to achieve response times below 20 ns and are able to protect the semiconductor laser from overload currents even during power-on and power off.

Abstract: An inverter-type ballast has built-in differential current transformer operative to sense any substantive difference in the currents flowing from each of its two output terminals. If a substantive difference exists for more than just a brief period, a trigger circuit operates to disable the inverter, thereby to remove voltage from the output terminals.