Abstract: A linear actuator system includes a linear actuator and an integrated pump assembly connected to the linear actuator to provide fluid to operate the linear actuator. The integrated pump assembly includes a pump with two fluid drivers, each fluid driver comprising a prime mover and a fluid displacement assembly to be driven by the prime mover such that fluid is transferred from a first port of the pump to a second port of the pump. The pump assembly also includes two valve assembles to isolate the pump from the system. The linear actuator system also includes a controller that establishes the pump in a normal mode of operation in which the prime movers are independently driven and switches to a fail-safe mode of operation in which only one prime mover is operated.

Abstract: A fluid system includes a variable-speed and/or a variable-torque pump to pump a fluid, at least one proportional control valve assembly, an actuator that is operated by the fluid to control a load, and a controller that establishes a speed and/or torque of the pump and a position of the at least one proportional control valve assembly. The pump includes at least one fluid driver that provides fluid to the actuator, which can be, e.g., a fluid-actuated cylinder, a fluid-driven motor or another type of fluid-driven actuator that controls a load. Each fluid driver includes a prime mover and a fluid displacement assembly. The fluid displacement assembly can be driven by the prime mover such that fluid is transferred from the inlet port to the outlet port of the pump.

Abstract: To provide a motor control circuit that variably controls the speed of a motor, in which an appropriate advance angle value corresponding to the speed of the motor that is set can be automatically set. The motor control circuit according to the present invention includes an advance angle setting means that adds a reference advance angle value to an advance angle correction value obtained by multiplying a proportional coefficient by a correction amount and outputs an advance angle setting signal, and an advance angle setting correction means that uses a ratio of a correction reference period relative to a period of a reference signal input from the outside as a correction amount and corrects the reference advance angle value by an advance angle correction value obtained by multiplying the correction amount by a predetermined proportional coefficient of the advance angle setting means.

Abstract: A synchronous transfer control system includes an arc resistant enclosure having a main housing having an open top portion and an arc plenum, the arc plenum having a closed front portion, a closed rear portion, and at least one open side portion, and a plurality of synchronous transfer control components housed within the main housing including: (i) a hard bussed first bus structured to be coupled to a first power source, (ii) a second power source, and (iii) a hard bussed second bus, wherein an output of the second power source is able to be selectively coupled to the second bus, wherein the first bus is able to be selectively and individually coupled to each of the motors, and wherein the second bus is able to be selectively and individually coupled to each of the motors.

Abstract: A robotic mount is configured to move an entertainment element such as a video display, a video projector or a staircase. The robotic mount is movable in three-dimensions, whereby the associated entertainment element is moveable in three-dimensional space. In one embodiment, a unitary display comprises a plurality of closely spaced individual displays which are mounted to robotic mounts, whereby the configuration of the unitary display may be altered by changing the position of one or more of the displays relative to the others.

Abstract: Each screen (1) of a group of screens is configured by a method in which a function is approximated, the function giving the instantaneous axial position (H(t)) of the load bar (2) thereof along an axis (Z) of translation in the form of a function having, as a variable, the instantaneous angular position (y(t)) of a winding device (4). The load bars of the screens are sequentially moved into a plurality of positions in which the load bars are aligned, and then the angular position (y(t)) of the winding device is determined. Next, the coefficients defining the approximation function of each screen are determined. The movement of the load bar of each screen is controlled by an instantaneous angular-position set value (?(t)), which is in turn predetermined from a representative profile using the one-to-one approximation function.

Abstract: A fan control system includes a fan and a fan control circuit. The fan control circuit includes a connector, a control unit, a switch unit, and a delay unit. The control unit is connected to the connector to receive a rotation speed control signal, and connected to the fan. The switch unit is connected to the connector to receive a voltage signal, and connected to the control unit. The delay unit is connected to the connector to receive the rotation speed control signal, and connected to the switch unit. When the delay unit receives the rotation speed control signal, the delay unit outputs a control signal to turn on the switch unit after a time delay, the voltage is transmitted to the control unit through the switch unit, the fan operates, the control unit controls rotation speed of the fan according to the rotation speed control signal.

Abstract: The invention relates to a method for starting an electronic drive circuit for the windings of an electric motor. A control unit, which is connected to a voltage source, is provided as well as a capacitor connected via a system switch element to the connecting terminals of the voltage source. The capacitor is connected across the input terminals parallel to the drive circuit. An operating circuit controls the system switch element. In order to start the motor, the operating circuit closes the system switch element and charges the capacitor and after the charging of the capacitor, opens the system switch element again. A test step is then started by the control unit, the drive circuit being supplied exclusively by the capacitor voltage (UC) during the test step.

Abstract: In a power converter a controller determines that an AC motor is in an abnormal state when a voltage of each phase of the AC motor detected by a voltage detector is in an unbalanced state where the voltage exceeds a predetermined value, and turns an opening/closing unit OFF to prevent damage generated in the AC motor from becoming worse. Moreover, the controller determines abnormality of the opening/closing unit based on a current of each phase detected by a current detector, and the controller performs control to reduce the number of revolutions of the AC motor upon determining that at least one of the AC motor and the opening/closing unit is in an abnormal state.

Abstract: The present invention is a method and system for monitoring the continuous flow of power delivered by multiple DC Direct current operated starter motors used to start engine driven electrical generators. The method and system comprise the closing of a starter battery system and an associated starter control switch, causing the starter battery system to discharge through a shunt whereby current is fed into a starter motor. The shunt is optionally provided as a precision resistor with a pre-calibrated voltage drop in millivolts DC proportional to a current passing through it. The shunt directs current to a meter relay, which is calibrated by establishing two set points, or desired trigger ranges, for the meter relay. If the current falls outside a range established by the two set points, then a meter relay alarm output is activated; and, if the current remains within the range, then the meter relay alarm output is not activated.

Abstract: A ventilator includes a base, a drive device disposed on the base, an impeller coupled to the drive device and driven by the drive device, and a cover assembled with the base to define a closed area between the cover and the base for receiving a first circuit board therein, wherein when an AC power source is input to the first circuit board to be converted, a DC power source is output to drive the drive device.

Abstract: A method to start at least two AC motors that are supplied from a common AC bus, which in turn is supplied from a power converter. At least one of the AC motors is an electrically excited synchronous motor including an excitation circuit. The synchronous motor is started first. During starting of remaining of the at least two AC motors a reactive power supplied by the power converter is determined and an increase of a field current or of a field voltage of the synchronous motor in linear dependence on the reactive power supplied by the power converter is determined. The increased field current or field voltage is applied to the excitation circuit of the synchronous motor.

Abstract: An electrical switching apparatus is for another apparatus including a number of insulators, a number of temperature sensors operatively associated with the number of insulators, and a number of conductors operatively associated with the number of insulators. The electrical switching apparatus includes a number of separable contacts, an operating mechanism structured to open and close the separable contacts, a number of sensors structured to sense a number of currents flowing through the separable contacts and through the conductors, a processor structured to input the sensed currents from the sensors, and an output. The processor calculates at least one of: (a) a thermal age of the other apparatus from a number of sensed temperatures from the temperature sensors, and (b) the thermal age of the other apparatus from the sensed currents. The output includes the thermal age of the other apparatus.

Abstract: A motor control circuit includes a manipulation unit, a control unit that drives a motor in a normal rotation direction or a reverse rotation direction, a catch detecting unit that detects a foreign substance caught in the opening and closing body, a first relay circuit that connects one of terminals of the motor to a power supply when the motor is driven in the normal rotation direction, a second relay circuit that connects the other terminal of the motor to the power supply when the motor is driven in the reverse rotation direction, a switch element that cuts off connection to the power supply when the normal rotation command is fed into the control unit from the manipulation unit, a detection circuit, and a feed circuit.

Abstract: A power limiting system for multiple electric motors includes an electrical power generating component, such as an alternator, and a plurality of motor controllers connected to an electrical bus. Each motor controller compares the voltage on the bus to a specified minimum voltage and a specified maximum voltage, and reduces its electric power output if the voltage on the bus is less than the maximum voltage while continuing to operate the electric motors.

Abstract: An automatic control mechanism for a group of motorized screens in which each screen includes a load bar that is displaced according to a predefined travel and wherein the control mechanism determines a shift parameter between a first reference position of each screen and a second reference position, one of these two reference positions being a reference position common to the screens of the group. The control mechanism takes into account at least one shift parameter to obtain, following a control command, at least the alignment of the load bars that have been displaced.

Abstract: A method for determining accuracy of an actual position of a plurality of independent motors in a printing press is provided. The method includes commanding each of the plurality of motors in the printing press via a controller to move a desired initial position, comparing an actual position of each motor to the desired initial position of each motor, determining if the actual position of each motor is within a predetermined tolerance of the desired initial position, and resetting any motor outside the predetermined tolerance to be within the predetermined tolerance. A printing press is also provided. The printing press includes a plurality of printing press components and a plurality of motors. Each motor drives at least one of the printing press components and each of the motors has a desired initial position. The printing press also includes a position detector for determining an actual position of the motor with respect to the desired initial position of the motor.

Abstract: A method for controlling a wheel speed of a locomotive includes determining an estimated wheel speed (52) for a desired wheel set of a locomotive responsive to a locomotive operating parameter indicative of an actual wheel speed of the desired wheel set. The method also includes generating a first adjustment parameter (e.g., 46) based on an operating condition of the locomotive, and then applying the first adjustment parameter to the estimated wheel speed for generating a first adjusted estimated wheel speed signal (54) used as a first input for controlling a wheel speed of at least one of the desired wheel set and the other wheel sets of the locomotive.

Abstract: A motor drive system for a sensorless motor includes a catch start sequencer that controls the motor drive system to robustly start the motor in the event the motor rotor is rotating in forward or reverse direction prior to activating the motor drive system. In particular, the catch start sequencer causes the motor drive system to initially find and track the rotor position, and then determines the speed and possibly the direction of rotation of the rotor. If the rotor is rotating in the reverse direction, the catch start sequencer controls the motor drive system to slow the speed of rotation and to then start the rotor rotating in the forward direction.

Abstract: A control system and method for ensuring proper closure of a dual swing gate. The control system employs position sensors for monitoring the position of each gate arm. A “differential position” is maintained between the arms during closing to ensure proper sequencing. The control system regulates the speed of the master arm and the slave arm to ensure that the differential position is maintained throughout the closure process.

Abstract: An electronic display configured to display visual information is mounted to a display mount. The display mount is movable in three-dimensions, whereby the associated display may be moved in three-dimensional space. In one embodiment, a unitary display comprises a plurality of closely spaced individual displays which are mounted to movable display mounts, whereby the configuration of the unitary display may be altered by changing the position of one or more of the displays relative to the others.

Abstract: An electrical control device is described.

Abstract: An electric engine starting system includes a permanent magnet motor that is used to start the engine and then to generate power for powering a load while the engine is running. A disclosed system includes a first phase controlled rectifier in series with a power converter and a second phase controlled rectifier. During an engine starting operation, the first phase controlled rectifier is switched to couple the permanent magnet motor to a power source for starting the engine. Once the engine is running, the first phase controlled rectifier is switched off and the second phase controlled rectifier is switched on. The second phase control rectifier converts variable AC power from the motor into DC power. The power converter converts the DC power into an appropriate power for driving the load. One disclosed example includes a filter between the power converter and the load to ensure that the load receives a selected quality of power.

Abstract: A synchronized rear vision system for a vehicle includes a pair of external side rearview mirrors for attachment to the vehicle and an interior rearview mirror for attachment to the vehicle. The synchronized rear vision system also includes a system master controller for detecting an instantaneous position of one of the side rearview mirrors and calculating position output signals for at least another one of the side rearview mirrors and the interior rearview mirror to automatically position at least the another one of the side rearview mirrors and the interior rearview mirror based on the instantaneous position. The synchronized rear vision system may include a controller to readjust the position of the rearview mirrors based on a position of a driver seat of the vehicle.

Abstract: A system for controlling lubricant displacement from a machine during turbomachine shutdown sequence includes a motor, a pump, a control valve, and a motor control unit. The motor is selectively energized from a power bus to rotate at a rotational speed and supply a drive force to the pump. The pump, in response to the drive force, draws fluid from a fluid and supplies the fluid to the machine. The control valve is movable between at least a first position, in which the control valve fluidly communicates the pump with a lubrication fluid source, and a second position, in which the control valve fluidly communicates the pump with a gaseous fluid source. During the shutdown sequence, the motor control unit controllably energizes the motor from the power bus to thereby control its rotational speed in accordance with a schedule that will displace at least a substantial volume of lubricant in the rotating machine with fluid from the gaseous fluid source.

Abstract: In a motor control apparatus in which a higher voltage is directly applied to a driving unit for a motor from a battery and a lower voltage stepped down by a switching regulator from the battery is also supplied to a control unit, the switching regulator is started its switching by a starting signal supplied from the outside of the motor control apparatus and is stopped its switching by the first stopping signal from the outside of a motor control apparatus and the second stopping signal derived from the control unit.

Abstract: A serial fan set and rotation speed-matching curve generation method thereof are provided. The serial fan set comprises a rotation speed control module, a first fan and a second fan, in which the rotation speed control module is used to receive the power signal and produce the rotation speed driving signal corresponding to the power signal in accordance with the relations of the rotation speed-matching curve, so that the first fan and the second fan are operated at the matching rotation speed, thus producing the optimum operation efficiency and achieving the purpose of controlling the serial fan set.

Abstract: The sensorless motor driving apparatus according to the invention may include: a timing generation circuit generating a timing signal at intervals T; a driving signal generation circuit receiving the timing signal and generating, at the intervals T, pulse signals, the number of which M (=m×L+k) is defined by a sum of a predetermined number k and a product of the number of statuses L of the rotor and an integer (m) equal to or greater than 1; and an amplitude control circuit switching between commutation patterns of the driving signal in synchronization with the pulse signals.

Abstract: A controller has a plurality of control units that are mutually connected by a communication line and are set at different places of an automobile, each corresponding to a different one of its power windows and serving to control its opening and closing. One of these control units is adapted to transmit a signal, in response to a switch operation, to another of the control units through the communication line to open or close the window corresponding to the latter control unit. When this control unit detects that it has submerged in water, it applies a constant voltage to an interface of the communication line. This prevents communications through the communication line and windows from moving in an unwanted manner.

Abstract: A device for monitoring the state of relay contacts is especially useful for controlling motor windings in air conditioning systems. When a first relay switch, which is operative to supply power to a first motor winding does not open as desired, a switch monitoring module responsively controls the second relay switch energization to prevent the second relay switch from being closed. This prevents power that would be supplied to a second motor winding from being also supplied to the first motor winding and causing potential damage to the first motor winding. A disclosed example includes an opto isolator that is energized only when the first relay switch is open as desired. The opto isolator controls an output signal to a second relay control portion, which only operates the second relay if the first relay has opened as required.

Abstract: A method of returning an electromechanical axial setting device, particularly suited for friction couplings. The axial setting device includes two setting rings centered on a common axis, one of which is axially held, with the other one being axially displaceably mounted, and one of which is rotationally fixedly held in a housing so as to be prevented from rotating, with the other one being rotatingly drivable. On their respective end faces facing one another, the two setting rings each include an identical multitude of circumferentially extending grooves. Each of the grooves, in a plan view of the end faces, define a depth which rises in the circumferential direction. Pairs of grooves in the setting rings each accommodate a ball. The rotatingly drivable setting ring is connected to an electric motor in respect of drive. The axially displaceable setting ring is loaded by pressure springs towards the axially held setting ring.

Abstract: A method and system that provides for simultaneous or independent start-up of two or more three-phase AC motors with reduced starting current. Two AC motors have their stator windings connected in series across the power network. If more than two AC motors are to be started, the stator windings of the additional motors are connected in parallel with the stator windings of one or both of the first two motors and the phase leads of the additional motors are connected to the power network. The voltage result vector is less than the sum of the rated voltage of each motor. After a preset time delay or when the motors reach a certain speed, the rated voltage is applied to each motor by disconnecting the stator windings from the series connection and connecting the stator windings of each motor in a delta configuration.

Abstract: A rotational speed of an electric motor 12 is memorized at a memory unit 21 as a set rotational speed for allowing a minimum required volume of brake fluid to be discharged from the pumps in a state where the output hydraulic pressure of the master cylinder is highest, and an energizing duty ratio for the electric motor 12 which is designed so as to rotate the electric motor 12 at the set rotational speed is determined at a duty ratio determining unit 22 in response to an applied voltage detected at a voltage detecting unit 20. A motor control unit 23 controls the energizing of the electric motor 12 from a battery 18 in accordance with the energizing duty ratio determined at the duty ratio determining unit 22.

Abstract: A fuel cell system includes a fuel cell unit having an anode side and a cathode side, anode-side feeding and outflow lines for the supply of fuel and removal of anode-side exhaust, and cathode-side feeding and outflow lines for the supply of oxygen and removal of cathode-side exhaust. The fuel cell system also includes means for electrically switching the fuel cell unit on and off depending on the available quantity of fuel.

Abstract: The present invention relates to an electronically adjustable actuator for actuating a plurality of actuating elements, such as valves. A control unit is provided for generating actuating signals to cause each of the valves to move with one another in a start-stop motion in accordance with a predetermined moving pattern. The control unit would measure each potential at the outermost lowest position of the valve and at the outermost highest position of the valve. A device is provided for determining the present potential percentage value of the different valve between the maximum potential as well as the minimum potential. This different value is used to determine whether an actuating signal would be used to drive each of the actuating elements in the start-stop motion.

Abstract: A hard disk drive for supplying a power supply voltage by monitoring a power supply voltage and method of controlling the same. The hard disk drive includes a power supply monitor circuit for monitoring an initially supplied power supply voltage, and a controller for supplying a prescribed reference voltage to the power supply monitor circuit, and for controlling the power supply voltage generated when initially activating a spindle motor by varying a permissible variation level of the power supply voltage of the power supply monitor circuit.

Abstract: A blower motor unit having a variable speed motor and that is suitable for direct, drop-in replacement in a residential HVAC (heating, ventilation, and air conditioning) system that employs a PSC motor. The blower motor unit is provided with a neutral input and two hot AC line connections, one for connection to the heating power source and the other to the cooling power source. The blower motor unit senses which of the inputs is energized by sensing either voltage or current on at least one of the inputs, selects one of at least two reference signals in accordance with which input is energized, and presents the control input of the replacement variable speed motor with the selected reference signal, thereby controlling the speed of the variable speed motor. This motor control unit, and the method by which it selects one of two signals for application to a control input of a motor, are also independently useful to control any type of motor having at least two modes of operation.

Abstract: A multiple electric motor hydraulic oil pump power system including a programmable controller having electric motor starting and stopping circuitry for hydraulic oil flow control. The circuitry having means to compare each electric motor running hours and select the motor with the least running hours to adjust oil flow to the desired amount. The system monitors oil pressure and flow, comparing such pressure and flow with the desired value and automatically adjusting the system to accomplish the correction. The controller also maintains safety sensing devices for high and low oil reservoir levels, oil filter condition limits, oil temperature limits, and means to maintain a constant oil pressure under load with load flow rates varying from very low to very high.

Abstract: A disk drive system for use in limited power applications is disclosed. The disk drive includes a spindle motor having two or more windings, along with a spindle motor driver which can drive the spindle motor in any of a unipolar, bipolar or tripolar mode. The bipolar or tripolar mode is used to start the disk drive and then the unipolar mode is used to operate the disk drive while data is being retrieved. By combining the three drive modes a large start current reduction and higher rotation velocities are achieved. Current consumption is further minimized by adaptively transitioning from bipolar to unipolar modes of operation. The disclosure also includes a general methodology for optimal motor K.sub.E and K.sub.M parameter selection.

Abstract: In a method of controlling activation of a motor, based on a device number (unit address) set value A.sub.d which is determined exclusively for a disk device and a motor activation start time delay T.sub.d which is designated by a host control device, a motor activation start time T.sub.s which corresponds to the physical device number is calculated in the disk device. The motor activation start time delay T.sub.d is set as a command in an interface between the disk device and the host control device. The method also requires that a nonvolatile memory is disposed in the disk device. The motor activation start time delay T.sub.d is stored in the nonvolatile memory when designated. In controlling activation of the motor later, the motor activation start time T.sub.s is calculated from the information which is stored in the nonvolatile memory.

Abstract: A multi-shaft driving apparatus includes a plurality of motors each for rotating one of a plurality of shafts to be synchronously rotated, an encoder, provided for each motor, for detecting a rotational state of the shafts, a pulse generator for generating a pulse signal for rotating the shafts, and a motor control circuit, provided for each motor, for inputting the pulse signal generated by the pulse generator for rotating the shafts and a pulse signal detected by the encoder and used as a feedback signal. The motor control circuit has a PLL control section and a rotational angle phasing section so that a rotational angle phasing control loop is generated to perform a rotational angle phasing operation by the rotational angle phasing section so to as place the shafts in position at a driving start and after performing the rotational angle phasing operation, a rising and steady control loop is generated to perform an operation from a rise state to a steady state by the PLL control section.

Abstract: A drive controller for a stepping motor having a plurality of excitation phases which designate stepping positions thereof, includes a motor driver for sequentially exciting the excitation phases to rotate the stepping motor in increments of one step angle, and a control section for controlling the motor driver to set an excitation interval. When the control section sets the excitation interval to be shorter than an interval of a stepping range in which the stepping motor temporarily stops for each increment, the stepping motor is driven in a slewing mode in which the rotation of the stepping motor is continued without stopping for each increment.

Abstract: In accordance with the invention, the functions of two TV cameras in the prior art for monitoring polymer coating concentricity and/or carbon coating thickness are accomplished by a single TV camera (48). Rather than being projected onto an opaque dispersive screen, the forward-scattered mode pattern of each of the orthogonal beams (57,58) is transmitted through a translucent screen (52,53) and reflected to an image combining device (67) which transmits both patterns to the single TV camera (48). The two beams are slightly vertically displaced to establish displaced images (72,73) of the two patterns. This allows the two patterns to be viewed simultaneously and distinguished by the TV camera. Modified electronics (FIG. 10) provide for alternate TV scanning of the two images so that a computer (22) can monitor and correct concentricity and/or carbon coating thickness in real time during fiber production.

Abstract: A mirror control system for electrically powered and positioned mirrors (FIG. 1) of the "memory" type for, for example, moving an automotive side view mirror from its current position to a desired "memory" position, and a special algorithm therefor (FIG. 2), which initially moves the mirror toward the final, desired position at a forty-five (45.degree.) degree angle to the vertical and horizontal axes (NE, NW, SW or SE; FIG. 6), for a mirror whose two directional motors have equal speeds (X=Y). If no obstruction (e.g., the mirror's edge) is encountered (FIG. 3), the mirror is moved by both motors until either the vertical or horizontal axis of the final position is encountered, at which axis intersection point the mirror is moved by only the appropriate one of the motors until the final point along the remaining axis is reached; this is the "normal" mode of the algorithm. However, if an obstruction is encountered (left side of FIG. 2; FIGS. 4 and 5), the mirror is moved at a 45.degree.

Abstract: A motor protection relay is provided which is programmable to limit the number of starts which are allowed in a given interval of time. In accordance with the algorithm associated with the relay microprocessor for controlling the starts per time, old starts which no longer fall within the same time constraint set by the operator or user are discarded and the time constraint is updated according to the next oldest start time.

Abstract: The present invention provides method and apparatus to control a plurality of DC motors each having an encoder by a sole microcomputer. The actual rotating speed of each DC motor is detected in response to the signal from the encoder. A pulse width of a voltage which is applied to each motor is controlled due to the deviation between the actual speed and a preset speed. The output signals from the encoders regarding a specific DC motor to the other DC motor are sequentially selected by a selection signal, thereby controlling the speed measurements and calculations regarding a plurality of DC motors and the duties of electric powers which are applied to the DC motors.

Abstract: An emergency battery power supply for a ring-spinning or ring-twisting frame can be brought into operation by an automatic circuit to bridge brief power failures and effect programmed shutdown of the motors upon longer power failures, with the speed ratios between the motors being maintained substantially to standstill to avoid yarn breakage during shutdown.

Abstract: In a drive system for a grinding mill the load torque plus frictional torque may increase considerably as a loaded mill is inched from its rest position and will suddenly decrease when the load tumbles or cascades. The applied torque or driving torque must increase at a corresponding rate and should also decrease when the load cascades. If the applied torque exceeds by a significant amount the load torque plus frictional torque, a destructive hammering will occur in the gear train and this will be generally proportional to the excess of applied torque for a synchronous motor drive. The drive system has a DC source which is commutated by a commutating device to provide a low frequency stepped alternating voltage to the stator windings of the synchronous motors of the drive system for inching. The output of the DC source has an alternating current component which varies as the difference between the applied torque and the load torque plus frictional torque.

Abstract: A direct current electric motor marine propulsion system is provided with a pair of shunt wound direct current electric motors which are alternatively connected in a series/parallel circuit configuration. A forward biased diode between the motors in the series circuit, provides for smooth switching characteristics. Fine control of low speed operation is accomplished through the use of a chopper in series with the power source. A contactor connected across the diode provides for reverse current flow during regenerative braking.

Abstract: A control for a plurality of air conditioning units installed in separate rooms of a multi-room building, with each air conditioning unit having an on-off switch to selectively connect the air conditioning unit to a source of electrical power. The control includes a switch for simultaneously interrupting the electrical power supplied to each air conditioning unit to place each unit in an off state. Once the supply of electrical power to each unit is renewed, each unit is prevented from restarting until the unit's on-off switch has been manually moved from its on position to its off position.