Abstract: A closed-loop control system for a DC motor includes a DC motor 12, a current sensor 14 for determining a current of the motor, a voltage sensor 32 for measuring a voltage of the motor 12, and a micro-controller 33. The micro-controller is constructed and arranged to (1) compare the determined current with a set point and output a pulse width modulated (PWM) duty cycle to control the motor, and (2) calculate a PWM duty cycle limit based on the measured voltage and compare the outputted PWM duty cycle to the PWM duty cycle limit such that when the outputted PWM duty cycle greater than the PWM duty cycle limit, the outputted PWM duty cycle is set to the PWM duty cycle limit. A method, in a DC motor, of preventing a current surge during severe voltage changes is also disclosed.

Abstract: A ventilator having a muting device includes a central processing unit, and a fan motor. The fan motor is connected to a start capacitor which is electrically connected to a temperature sensing circuit which is electrically connected to the central processing unit, so that the start capacitor can indicate a signal on a panel of the ventilator, so as to control a rotational speed of the fan motor. Thus, the operation state of each part of the ventilator is indicated on the panel of the ventilator clearly to facilitate inspection of the user, so that the user can control the rotational speed of the fan motor to a proper value, thereby reducing the noise during operation, so as to achieve a muting effect.

Abstract: A drive control system for a multiphase motor powered by a power converter of a type including a multi-pulsed bridge circuit with a plurality of controllable converter valves and a same number of electrically isolating devices, includes a control unit, with the input side of the converter valves connected to the output side of the control unit via the electrically isolating devices, and an armature short-circuit braking device for connection to the input side of electrically isolating devices of one bridge side of the bridge circuit. An overvoltage recognition device is provided to receive a signal commensurate with a limit value, and a signal commensurate with a determined actual input voltage of the power converter. A trigger circuit is connected to the armature short-circuit braking device, and has an input connected to an output of the overvoltage recognition device and supplied with a signal for the armature short-circuit braking device.

Abstract: A power conversion device that limits an inrush current while reducing overall weight and volume of the device even under a high rated power. One and the other ends of an initial charging circuit having a DC power source, a switch, and a diode connected in series are connected to an inductive load and a lower potential source line, respectively in a power conversion device. The initial charge controller unit turns ON and OFF one switching element of the power conversion device repeatedly during an initial charging operation prior to the normal operation. As a result, a charging current flowing through the initial charging circuit is supplied to a capacitor through the inductive load repeatedly. After the capacitor is sufficiently charged, the initial charging operation is finished and the normal operation is started.

Abstract: A dual hoist bucket crane controller for operating a closing motor and a holding motor using a close inverter adapted to control the closing motor and a hold inverter adapted to control the holding motor where the hold inverter and the close inverter are internally controlled and operate independently from the other drive. Also covered is a dual hoist bucket crane controller for operating a closing motor and a holding motor using a dual axis master switch adapted to provide a close inverter input signal to the close inverter and a hold inverter input signal to the hold inverter.

Abstract: The invention relates to a drive unit for a closure of an open roof construction. It comprises an electric motor having a drive shaft and transmission means and an electric circuit including said motor and control means to actuate the motor. An emergency clutch is coupled to at least one of the drive shaft and the transmission means and is reachable to enable hand actuation of the movable part in case of an emergency. The emergency clutch is covered by a part of the electric circuit, which must be disconnected to reach the clutch. The part of the electronic circuit is provided on a breakable seal, which is a pierceable metal foil strip. As a result it is possible to observe the use of the clutch, either visibly or electronically.

Abstract: A circuit for disconnecting a neutral point of an electric machine includes an inductance connected to a lead of the electric machine; a three-terminal solid-state switch that has a first terminal connected to the inductance, a second terminal connected to the neutral point, and a third terminal for controlling a flow of current between the first and second terminals; a controlling circuit coupled to the three-terminal solid-state switch that includes a first loop that has a power source, a resistance, and a voltage regulator to maintain a first voltage upon the third terminal, and a second loop that has a power source, a resistance, and a trigger switch being controllably switched on to thereby close the first loop whereby a second voltage is applied to the three-terminal solid-state switch to thereby substantially electrically disconnect the first terminal from the second terminal.

Abstract: A device for monitoring operation of a driving arrangement including at least a servo-mechanism, which includes a regulator, a driving motor controlled by the regulator, and an element which can be set in motion by the driving motor. A detection arrangement detects deviations between intended and actual movement positions of the element and an operation inhibiting and/or alarming arrangement inhibits operation of the driving arrangement and/or starts an alarm when impermissible deviations are detected. The monitoring device includes a redundant driving arrangement, which include at least one auxiliary servomechanism including a redundant regulator, a redundant driving motor controlled by the redundant regulator, and a redundant element which can be set in motion by the redundant driving motor.

Abstract: The presence of an object in the path of an automotive vehicle window is detected. This is accomplished by sensing or observing a system variable, such as speed or motor current, and comparing this measured value to a predicted limit value of the system variable which is based upon the behavior of the system variable when there is no object present. The values are compared over predetermined time intervals and if the measured value falls out of the predicted limit value of the system variable in a direction that indicates an obstruction, then a control system detects the presence of an object and reacts accordingly by stopping or reversing the drive motor of the vehicle window.

Abstract: A method for determining the position of a movable element to be driven by a direct current motor between first and second positions includes counting ripples contained in a motor current signal as the motor rotates to drive the element. The position of the element is determined based on the counted ripples. The motor actuates, until the current signal is void of ripples, to move the element into the first position when the element is to be moved out of the first position towards the second position. The counted ripples is reset to a reset value after the motor has been actuated to move the element into the first position such that the reset value corresponds to the position of the element being in the first position. The motor actuates to move the element towards the second position after the counted ripples has been reset.

Abstract: A motor for moving a flap for distributing a flow of air in a duct of a heating, ventilation and/or air conditioning installation is supplied with voltage. A power-regulation module is mounted in series with the motor, and includes at least one positive-temperature-coefficient resistor, so that, when the flap reaches an open or closed position, the motor is blocked. This results in an increase in the current strength in the circuit, causing an increase in the value of the resistance, and this results in a reduction in the current strength and in the voltage at the terminals of the motor.

Abstract: A solar system for a motor vehicle, which is provided with a solar generator and a DC/DC converter unit, the solar system being switchable for supplying a power consuming device in the motor vehicle or for recharging of the motor vehicle battery. The DC/DC converter unit is made with two poles on the output side and functionally comprises a first and a second DC/DC converter which are respectively optimized with respect to the supply function of the power consuming device and the recharging function, there being a changeover unit which acquires the voltage at the output of the DC/DC converter unit and switches the output depending on the acquired voltage to either the first DC/DC converter or the second DC/DC converter.

Abstract: A method for the electronic monitoring and control of the opening and closing operation of electrically operated aggregates, particularly of window lifters and sunroofs in motor vehicles, is described. A regulating unit of the aggregate is connected to a vehicle electrical system. The regulating unit is directly influenceable via electrical operating control elements, i.e., via a control-electronics interfacing circuitry connected to the aggregate. The control electronics interfacing circuitry is supplied with a signal that is a function of an accelerative force acting on a motor-vehicle body. The signal which is a function of the accelerative force, is determined from a motor speed of the regulating unit.

Abstract: An inverter device and a motor driving device are arranged to have an inrush current prevention circuit for preventing an inrush current from flowing into a smoothing circuit when the power is turned on. The inrush current prevention circuit includes a current limiter for limiting the inrush current, a plurality of semiconductor switching elements, and an inrush current prevention circuit driving -circuit for driving the plurality of semiconductor switching elements, the semiconductor switching elements being connected together.

Abstract: A DC motor is connected to diagonal positions of a bridge circuit having of four sides including switching elements and reflux diodes. At least one of two terminals is connected to a power line, and at least the other terminal is grounded. By performing pulse width modulation control of the switching elements, operation of the DC motor is controlled. When the DC motor is in operation, the sum of the terminal voltages of the DC motor is equal to the power voltage. When the DC motor is out of operation, the sum of the voltages is set to a predetermined voltage. If the sum of the voltages has deviated from the power voltage or the predetermined voltage by at least a predetermined value, the occurrence of a malfunction is judged.

Abstract: A circuit for operating an electric motor (11) includes a monitoring arrangement (24) for ascertaining an increased load state of the electric motor (11). The monitoring arrangement (24) compares an rpm difference (ND) between a predetermined nominal rpm value (NSOLL) and an actual rpm value signal (NIST) with a predetermined limit value. If the limit value is exceeded, the monitoring arrangement (24) emits an overload signal (25) that reduces the nominal rpm value (NSOLL) or a control variable (SN) supplied to a drive stage (18), or drops it to zero. The circuit is particularly suited for use with a fan, in which instance the ventilator (22) cools the electric motor (11) and/or the drive stage (18).

Abstract: In the embodiment described in the specification, a fault tolerant motor drive circuit arrangement includes a motor having three stator windings which are electrically isolated and are supplied by separate single phase drive circuits, each having a differential current sensor detecting current in both circuit conductors and an overcurrent sensor in one circuit conductor, along with a ground connection for each circuit having a ground conductor with an overcurrent sensor and a high resistance with a voltage sensor across the high resistance. A monitoring unit receives signals from all of the differential current sensors, overcurrent sensors and voltage sensors to provide indications of the location of insulation faults or incipient faults in the windings.

Abstract: A power steering system and induction motor load compensation algorithm or processing method for use in a vehicle. The power steering system comprises a power supply, a power steering motor, a steering subsystem, and a power steering controller coupled to the power supply. The controller processes a frequency command input corresponding to the power steering frequency requested by the steering subsystem and data contained in one or more software lookup tables to adjust the output frequency produced by the power supply to control the speed of the power steering, motor. The lookup tables are generated empirically and characterize the output power of the power supply at different system pressures over a range of motor speeds. The software lookup tables provide a power band that implements a power limiting state machine.

Abstract: A power module which enables the effective use of the operation range of each power element. The power module having power elements for driving a motor, self protection means for protecting the power module from a plurality of predetermined abnormal phenomena, and power element drive means for driving and controlling the power elements based on a drive signal from an external unit and the output of the self protection means comprises: decision value storage means for storing decision values for the detection of the plurality of predetermined abnormal phenomena by the self protection means; and information transmission means for receiving the decision values set by the external unit, outputting them to the decision value storage means and outputting the decision values stored in the decision value storage means to the external unit.

Abstract: An apparatus for controlling a current limiter of a motor for protecting the motor by limiting the amount of electric current supplied to the motor and controlling a driving force of the motor comprises of: a frequency detector for detecting the rotational frequency of the motor; a limiter controller for generating a current limiter control signal corresponding to the rotational frequency detected by the frequency detector; and a current limiter for limiting the amount of current supplied to the motor by the current limiter control signal. The current limiter of the motor is controlled by a pulse-width modulated signal in which the duty cycle changes, i.e., a PWM signal, according to the rotational speed of the motor so that a load state or deviation of an axial load of the motor is minimized to accurately control the motor.

Abstract: A motor overload coil control is disclosed for use in a motor starter/relay contactor. The control includes an 8-bit, 8-pin microcontroller that together with an I/O reduction circuit, is capable of functioning 13 I/O's with only 5 I/O pins on the microcontroller. Three remote signals are prioritized and reduced on one input line to the microcontroller. The control includes three-phase current measurement from three Hall effect current sensors positioned one on each leg. The system includes current integration to provide a single current input to the microcontroller. A full load amperage (FLA) adjustment allows use on a wide range of motors. The microcontroller uses the FLA adjustment and the current signal to find an appropriate I2t value for real-time monitoring of the operating temperature of the motor. A status indicator is provided having an LED output to show the status of the system and indicate the motor temperature, when appropriate.

Abstract: In a controller, for use in an electric motor, which self-contains a current control system, a conducting portion of a feedback element from a current detector up to a summing point, and a conducting portion of a forward element from the summing point for the current control up to a gate terminal of each of switching devices are mounted in a power module to be hermetically encapsulated without being exposed to the external ambient atmosphere. The distributed processing is executed in the two portions, i.e., a current control loop, and a position control unit, a velocity control unit and an interface processing unit other than the current control loop. Therefore, the current control loop including the current feedback portion is constituted by another sub-microprocessor to be mounted together with the associated devices in a power module which is molded with resin such as epoxy resin.

Abstract: A speed control device for a cooling fan and a method of control thereof are disclosed, in which temperature and noise among other factors are taken into consideration, whereby changes to the voltage/current of power supply provided to the cooling fan are used to adjust the speed of the cooling fan. The speed is reduced as much as possible within the permissible range of system temperature to minimize the noise generated from the cooling fan. When the temperature exceeds the permissible range, the speed of the cooling fan is accelerated to reduce system temperature.

Abstract: A motor controller for controlling currents flowing to a motor by the PWM system includes interruption-restart controller for interrupting supply of PWM commands for at least one phase when the actual current flowing in at least one motor phase has exceeded a specified value, and for thereafter restarting PWM command supply. When the actual current flowing to the motor has reached a previously determined anomalous level, control is performed to interrupt and restart supply of PWM commands. By interrupting the supply of the PWM commands, the current flowing to the motor is returned from an anomalous level to a normal level and the equipment protected. After the motor current is returned to a normal level by the interruption of PWM command supply, PWM command supply is resumed, normal control by PWM command is again performed, and a non-controlling state in the controller is avoided.

Abstract: Apparatus providing a control and protection arrangement for walking/running exercise machines which is effective to provide protection against malfunction conditions which may be experienced by the exercise machines, to thereby protect users of the exercise machine against injuries. The present invention provides an efficient response time to motor speed variations to provide greater user safety.

Abstract: In a stop and jamming detection system in an electric motor, in particular a stepping or commutator motor, a parameter is determined by current measurement, from the profile of the instantaneous current by comparison with a reference value, as a signal for the stop and jamming detection system. In addition to sensing the current flowing through a winding of the motor, the instantaneous operating voltage and the resistance of the motor winding are sensed. All three parameters are conveyed to an analysis circuit. By comparison with reference values, a determination is made by the analysis circuit as to whether the motor is jammed or movable. Reliable and economical stop and jamming detection system for an electric motor, which is used in particular in a wide variety of operating conditions in motor vehicles.

Abstract: The variable frequency drive of a motor monitors pulse generator feedback while the motor is stopped and an electromechanical brake is set. When the pulse generator feedback exceeds a predetermined level indicative of brake failure, tie controller actuates the motor to operate in zero servo mode and maintain the load. An alarm is also sounded, allowing an operator to safely lower the load.

Abstract: The present invention relates to a control circuit for motor of electric jogging device in which a safety switch is disposed between an electronic loop and a power switch and which has an inserted safety plug-in pin to connect the power in an ON state. Accordingly, when the safety plug-in is removed from the fastening position, the second safety switch will be shut down in an OFF state so that the power won't enter into the electronic loop again and the motor won't be driven, and the safety of the user can be ensured.

Abstract: A windshield wiping device includes a control amplifier 5 for controlling a wiper motor 7 in accordance with a driver's operation of a wiper switch 3. When a vehicle is energized, the control amplifier 5 once outputs a working inhibition signal to a working inhibition relay 15 in order to stop the operation of the wiper. Thus, it is possible to avoid the wiper's working against the driver's will immediately after a key switch has been switched on. When the vehicle begins to travel or the position of the wiper switch 3 is changed by the driver, then the wiper is activated in accordance with the position of the wiper switch 3.

Abstract: A controller for energizing a power-operable element, such as a sunroof, window, door, vehicle seat, a component of a major appliance or of a machine or of a conveyor system. The disclosed controller senses both hard and soft obstructions and de-activates or otherwise alters operation of a motor that drives the element when an obstruction is detected. The controller can also be used to actuate a brake. The controller senses obstructions during start-up of the motor and regulates the speed of the power-operable element by pulse width modulating motor energization signals.

Abstract: An electric motor control circuit that prevents lowering of a motor's rotation speed when a load is applied in the case where a rotation speed is adjusted within a range that doesn't exceed a predetermined upper limit of rotation speed. When a base current of a transistor Q1 starts to flow in response to operation of a trigger switch 3, transistor Q1 turns on and a setting signal output from a switch S2 which sets the upper limit rotation of a motor M is bypassed via a bypass way 22 by transistor Q1. Thus, a signal level of the setting signal inputted to an operational amplifier 7 is changed, and output timing of a pulse signal output from a phase control circuit 5 to a gate pulse output circuit 9 is changed and a conducting angle of a triac Q2 is controlled. Because the trigger switch 3 does not adjust an output level of operational amplifier 7, the rotation speed of motor M does not decrease when the load is applied.

Abstract: A method for controlling the operation of a brushless DC fan for cooling heat generating components of a system is provided. The method includes providing a system temperature signal indicative of a system temperature and providing an intelligent shutdown enable signal. The system temperature signal is compared with a shutdown temperature signal if the intelligent shutdown enable signal has a first value. The shutdown temperature signal is representative of a shutdown temperature value. The fan is operated at a generally temperature proportional speed after comparing the system temperature signal with the shutdown temperature signal if the system temperature as indicated by the system temperature signal is greater than the shutdown temperature value as indicated by the shutdown temperature signal.

Abstract: The present invention involves a refrigeration system. The refrigeration system comprises an electrical compressor motor, a line adapted to be connected to an electrical power line and a thermostat control circuit. The thermostat control circuit comprises a thermostat responsive logic circuitry coupled to a temperature sensor associated with the compressor and a solid state motor control circuit. The solid state motor control circuit includes a relay circuitry, power switch circuitry, compressor starting circuitry with an overload timer, high voltage protection circuitry, under voltage protection circuitry and run current limiting circuitry. The relay circuitry includes an optical coupler and triac to provide line voltage to the compressor through a start resistor. The power switch circuitry includes a pair of SCR's connected in parallel as a switch to allow current to flow through the compressor.

Abstract: A library apparatus having a motor driving control circuit including a processor, a motor driver circuit, a relay, a motor abnormal condition detection circuit, a current control circuit, an excess current detection circuit, and an abnormal current monitor circuit. The motor abnormal condition detection circuit is connected to the motor driver circuit, and detects an abnormal condition of at least one of the motor and the motor driver circuit. Upon detecting an abnormal condition, the motor abnormal condition detection circuit outputs a motor abnormal condition detection signal which prompts the current control circuit to regulate the current flowing through the motor driver circuit. If the current control circuit is unsuccessful, the excess current detection circuit outputs an excess current detection signal which triggers the relay to close the power source circuit of the motor driver circuit.

Abstract: A fan control device includes a fan rotation control circuit adapted to be connected electrically to a fan and adapted to control activation and deactivation of the fan. The fan rotation control circuit generates a voltage output corresponding to driving current flowing through the fan to indicate operating speed of the fan. A comparator circuit is connected to the fan rotation control circuit and is operable so as to perform a comparison operation in order to compare the voltage output of the fan rotation control circuit with a reference speed signal, and so as to generate a logic output corresponding to result of the comparison operation. A processor receives the logic output of the comparator circuit, and controls the fan rotation control circuit to deactivate the fan upon determining that the operating speed of the fan is abnormally slow, indicating that the fan is in a near-breakdown condition, based on the logic output of the comparator circuit.

Abstract: A circuit for driving a three-phase brushless DC motor (301) includes a neutral point feedback circuit (201) which operates a three-phase output circuit (202) so that a neutral point potential (V.sub.C) of the motor (301) is maintained at a predetermined potential, and a neutral point potential comparison circuit (500) which determines whether or not the neutral point potential (V.sub.C) is between reference potentials (V.sub.ref1, V.sub.ref2). If the neutral point potential (V.sub.C) is not between the reference potentials (V.sub.ref1, V.sub.ref2), a switch shutoff signal (SC) is activated to turn off a switch (106), so that a current (I.sub.C) is not provided to the neutral point feedback circuit (201). Accordingly, the neutral point feedback circuit (201) stops flowing currents (I.sub.A, I.sub.B) to the three-phase output circuit (202) which in turn stops driving the motor (301). The circuit for driving the motor (301) is prevented from being broken down if a short circuit occurs in the motor (301).

Abstract: An ac machine monitor, particularly applicable to ac induction motors, provides information for ascertaining the health and condition of the motor. The monitor is self-contained, having its own internal power source, electronics, and sensor suite, and attaches directly to the outer frame of the motor. Sensors disposed within the monitor include a motor frame temperature sensor, flux sensor, vibration sensor, and clock. The flux sensor includes a substantially planar substrate onto which a conductive trace is attached as the flux sensing element. Sensor outputs are processed and analyzed by monitor electronics to determine various life history parameters, including motor speed and load, which are stored in electronic memory. A communications port enables a peripheral device, such as a notebook computer or portable data collector, to communicate with the monitor and download the life history parameters stored in memory.

Abstract: An inverting amplifier circuit generates a comparison voltage by comparing a smoothed voltage of a voltage across a semiconductor switching element and a setting voltage that is generated by device of a voltage setting volume. An operational amplifier generates a drive signal by comparing the above comparison voltage and a triangular voltage. Negative feedback is effected so that the setting voltage becomes equal to the smoothed voltage, which is inversely proportional to the rotation speed of a DC motor.

Abstract: A circuit for driving a voice coil motor used to position the heads of a disk drive is disclosed. The circuit consists of a an H-bridge circuit, a controller, and a feedback loop. The feedback loop prevents the BEMF from driving a voltage on the voice coil motor above the supply voltage.

Abstract: A temperature-compensating overcurrent detection circuit for a DC motor comprising a converter, an integrator and an overcurrent detector. The present invention provides for an overcurrent detection circuit for a DC motor that is adapted compensate for operating temperature of the motor's environment and such compensating detection circuit does not respond with an early forcible operation when the mechanical device is constrained. The overcurrent detection circuit is adapted to permit the motor to carry out its intended operation exactly without having malfunctions due to noise and a temporary overcurrent.

Abstract: A time-compensated overcurrent detection circuit shuts off a D.C. motor during large overcurrent conditions caused by actual constraints on the motor. The circuit prevents premature motor shut off by establishing a minimum activation time for shutting off the D.C. motor. An overcurrent time compensator establishes a minimum time period for activating a motor reset signal after sensing an overcurrent condition. The circuitry uses a relatively small capacitor that provides quick response to overcurrent conditions.

Abstract: A motor control circuit comprises a current command circuit generates a current command signal proportional to a selected motor speed. A comparator generates a comparator output signal proportional to the difference between the current command signal and a signal proportional to current flow in the motor. An output terminal of the comparator is operatively connected to a logic circuit which generates a control signal having a duty cycle that varies proportional to the comparator output signal. A drive circuit has an input terminal to which the control signal is applied and an output terminal connected to the motor. The drive circuit generates a motor drive signal proportional to the control signal for driving said motor. A current command control circuit has an input terminal to which the current control signal is applied and an output terminal to which the current command signal is applied.

Abstract: A device for controlling and regulating the relative speed between the scroll (4) and drum (2) of a centrifugal extractor, comprising a dc or ac electric motor (10), stator (10a) of which is made integral with drum (2) and rotor (10b) of which is made integral with a gear (7) which drives scroll (4) via appropriate means (7a, 8a, 14a; 7b, 8b, 14b) of connection, there being furthermore provided means (30a, 30b) for detecting the speeds of rotation of such rotor (10b) and stator (10a) and for converting them into a representative electric signal, and means (40, 50) for comparing such electric signals designed to emit a signal (D.sub.rs) capable of operating means (60; 1060) for supplying to rotor (10b) a current capable of compensating for any deviations of the parameters of the extractor from the programmed operating conditions.

Abstract: An on-car motor driving apparatus is equipped with a motor for moving a moving unit such as a window of a motor car, a motor driving controller which controls the revolution, stop, and rotational direction of the motor, and a current measuring and comparing device which measures the variation in current per unit time of the motor and compares the measured variation in current with a preset value. The on-car motor driving apparatus stops the revolution of the motor and/or reverses the rotational direction of the motor through the motor driving controller. The apparatus is further equipped with a voltage measuring device for measuring motor driving voltage and a voltage-based time setting device which changes the length of the unit time in accordance with the driving voltage value measured by the voltage measuring device. Line voltage is supplied to a differential amplifier only when the line voltage is supplied to the motor.

Abstract: A safety guard for a pedestrian-operated or riding machine having rotatable blades and incorporating a strip switch for disabling the motor of the machine upon sensing the presence of an operator's body part or other foreign object in contact with a side of the housing or between the housing of the machine and the ground. The strip switch is secured to the housing and is oriented to be actuated when the machine overruns or contacts a foreign object. Upon actuation, the strip switch disables operation of the motor to prevent the machine's rotating blades or other moving parts below the housing of the machine from striking the foreign object. Another approach to minimizing injury from machinery having rotatable blades is to provide a semi-rigid guard which is attached to the machine body and movable in a forward movement and away from the ground while preventing lateral movement of objects under the machine.

Abstract: Between one end of a motor coil and the ground, a drive transistor is connected. When the drive transistor is turned off, and in particular at the moment when a current flowing through the motor coil drops to zero, a back electromotive force is induced at said one end of the motor coil. The back electromotive force is clamped by a pnp-type transistor with its base supplied with a constant voltage and its emitter connected to said one end of the motor coil.

Abstract: A speed limiting system for a vehicle such as a forklift truck enables the travel speed of the vehicle to be limited without limiting maximum throttle position or adjusting a governor to limit maximum engine or motor power. The system can be used with combustion engine vehicles or electric vehicles. The system has a rate of travel sensor, preferably a rotation sensor sensing a rotation rate of the vehicle axle or wheel. A rate of travel signal is provided to either an analog or digital speed limiting control system which outputs a logic high speed control signal when the rate of travel signal exceeds a pre-set overspeed limit value for a selected time period. The speed control signal can be used to display or record occurrences of overspeed vehicle travel, or limit engine or motor power in that presence of the speed control signal. A warning system can also be incorporated to warn of high speed travel which is potentially approaching an overspeed condition.

Abstract: A device for the optimizing of the speed control of an electric subfractional horsepower motor for dental instruments is provided wherein it is possible to operate the motor in any desired speed range. The device contains a first module for regulating the speed by voltage measurement, a second module for regulating the speed by current-load compensation, and means for deciding which of the two modules and in what proportion they assume speed regulation of the motor.

Abstract: A diagnostic tool may be attached to the control panel of a piece of machinery within a plant or factory which includes an electric motor. The diagnostic tool includes indicators for providing information to an operator of the equipment for which the control panel provides power. These indicators inform the operator of various modes of operation of the control circuitry within the control panel which regulate the power going to the motor. In this manner, the operator may determine if the machinery is ready to run, and if not, if it is necessary to call a technician.

Abstract: An electric motor control circuit that prevents lowering of a motor's rotation speed when a load is applied in the case where a rotation speed is adjusted within a range that doesn't exceed a predetermined upper limit of rotation speed. When a base current of a transistor Q1 starts to flow in response to operation of a trigger switch 3, transistor Q1 turns on and a setting signal output from a switch S2 which sets the upper limit rotation of a motor M is bypassed via a bypass way 22 by transistor Q1. Thus, a signal level of the setting signal inputted to an operational amplifier 7 is changed, and output timing of a pulse signal output from a phase control circuit 5 to a gate pulse output circuit 9 is changed and a conducting angle of a triac Q2 is controlled. Because the trigger switch 3 does not adjust an output level of operational amplifier 7, the rotation speed of motor M does not decrease when the load is applied.