Abstract: A method for dynamic braking of a permanent magnet motor, and an elevator utilizing thereof, are presented. The arrangement includes a corresponding number of phase legs and input connectors relative to a number of the plurality of motor windings, wherein each one of the input connectors is coupled to a respective one of the phase legs. At least some of the phase legs comprise at least two semiconductor devices. Second terminals of the phase legs are connected to each other, wherein the arrangement includes a number of semiconductor switches configured for forming a short-circuit between each of the plurality of motor windings.

Abstract: The invention relates to a device for the rapid reactivation of a helicopter turbine engine (6), characterised in that it comprises a pneumatic turbine (7) mechanically connected to said turbine engine (6) so as to be able to rotate it and ensure reactivation thereof; a pneumatic storage (9) connected to said pneumatic turbine (7) by means of a pneumatic circuit (10) for supplying pressurised gas to said pneumatic turbine (7); a controlled fast-opening pneumatic valve (11) arranged on the pneumatic circuit (10) between said storage (9) and said pneumatic turbine (7) and suitable for being on demand placed at least in an open position in which the gas can supply said pneumatic turbine (7), or in a closed position in which said pneumatic turbine (7) is no longer supplied with pressurised gas.

Abstract: A system includes a converter operatively connected to an alternating current (AC) power source and a direct current (DC) bus, an inverter operatively connected to a motor and the DC bus, and a controller. The converter includes a first plurality of switching devices in selective communication with each phase of the AC power source and the DC bus. The inverter includes a second plurality of switching devices in selective communication with each phase of a plurality of phases of the motor and the DC bus. The controller is operable to command dropping of a brake through a passive delay circuit responsive to detection of an emergency stop condition for a load driven by the motor and reduce a voltage on the DC bus by dropping at least one phase of the AC power source and/or using a dynamic braking resistor prior to the brake physically dropping.

Abstract: A unit for installation in a complex product comprising an electric machine requiring an AC power supply. The unit comprises: a housing carrying an AC output; a battery in the housing comprising at least one battery cell; an inverter in the housing, the inverter comprising a plurality of voltage controlled impedances, VCIs, for providing a power supply to the AC output based on energy from the battery; wherein the housing carries a timing signal input configured to receive a timing signal from outside the housing; and wherein the timing signal input is coupled to control the VCIs so that changes in the impedances of the VCIs are synchronised with the timing signal.

Abstract: A braking energy recovery system (50) for an electric motor (62) comprises first regulator (52), energy storage device (54), second regulator (56), sensor (60), and controller (58). The first regulator (52) outputs a DC link voltage to the energy storage device (54). The second regulator (56) couples to the energy storage device and outputs a motor drive signal to the electric motor (62). The sensor (60) senses an operating characteristic of the electric motor. The controller (58) outputs to the first regulator an energy management signal (74) that comprises a time variant signal as a function of (i) motor speed and/or (ii) back EMF determined via the sensed characteristic, whereby the first regulator dynamically regulates the DC link voltage to maintain substantially constant an energy balance that comprises a sum of (a) rotational and/or linear kinetic energy of the electric motor and (b) energy stored in the energy storage device.

Abstract: A variable frequency motor drive system configured such that the dc link capacitor charge is increased gradually, thus avoiding the above-mentioned transients. In the most preferred embodiment, the present invention ensures a gradual increase in the rectified voltage by providing the rectifier as a half-controlled thyristor rectifier (SCR) in place of the standard diode rectifier.

Abstract: A high-voltage direct-current (HVDC) transmission system includes an alternating current (AC) electrical source and a power converter channel that includes an AC-DC converter electrically coupled to the electrical source and a DC-AC inverter electrically coupled to the AC-DC converter. The AC-DC converter and the DC-AC inverter each include a plurality of legs that includes at least one switching device. The power converter channel further includes a commutating circuit communicatively coupled to one or more switching devices. The commutating circuit is configured to “switch on” one of the switching devices during a first portion of a cycle of the H-bridge switching circuits and “switch off” the switching device during a second portion of the cycle of the first and second H-bridge switching circuits.

Abstract: A regenerative brake control system of an electric motorcycle comprises an electric motor, sensors for detecting vehicle states of the electric motorcycle, and a control unit which sets target regenerative torque based on the vehicle states, when a regeneration condition is satisfied, and performs asymptotic control in such a manner that a torque command provided to the electric motor gets gradually close to the target regenerative torque with a passage of time.

Abstract: The invention relates to a method of control implemented in a variable speed drive, said method comprising the following steps of: for a switching of a transistor (100) of the rectifier stage (1), determination of a first control signal (Ce) corresponding to a first gate current (Ige) to be applied to the gate of the transistor to be switched so as to act on the rate of the variation of a first voltage (Vrec) generated by the switching, for a switching of a transistor (200) of the inverter stage (2), determination of a second control signal (Cs) corresponding to a second gate current to be applied to the gate of the transistor to be switched so as to act on the rate of the variation of a second voltage (Vinv) generated by the switching, determination of a first instant of switching (te) of the transistor of the rectifier stage and of a second instant of switching (ts) of the transistor of the inverter stage (2), the first control signal (Ce), the second control signal (Cs), the first instant of switching a

Abstract: An apparatus and method for drastically increasing the efficiency of a single phase AC motor. A DC solid state driver is used to pulse a combination of the motor coil and a series capacitor. The coil/capacitor combination allows the motor to run near resonance (or a multiple of resonance). This results in a flywheel effect that only requires pulses at the proper time to keep it going. The solid state driver is powered by pulsed DC at around 150 volts peak and clocked at 60 Hz by a square wave timing circuit.

Abstract: A motor drive device (1) of the present invention includes a converter unit (10) and an inverter unit (30). The converter unit (10) includes: power supply voltage monitoring unit (3) for detecting a power failure; DC link voltage detecting means (4); capacitor total capacity calculating means (6) which calculates total capacity of DC link smoothing capacitors (17, 18) and calculates a DC link low-voltage alarm detection level for an instantaneous power failure; DC link low-voltage alarm detection level setting means (8) which varies the DC link low-voltage alarm detection level for an instantaneous power failure as necessary; and alarm generating means (7) which monitors the DC link voltage and generates an alarm to protect the converter unit. In the case where a power failure is detected, the DC link low-voltage alarm detection level is increased in accordance with the total capacity of the DC link smoothing capacitors (17, 18).

Abstract: A data processor establishes a first range of rotational speeds of a rotor of the motor from a first lower limit to a first higher limit and a second range of rotational speeds from a second lower limit to a second higher limit. A hysteresis band or a rotational range of speeds is established such that during operation in the first range the first higher limit is adjusted (e.g., raised by a first amount to be greater than the second lower limit). A sensor detects or measures a rotational speed of a rotor of the motor. The data processor determines whether the measured rotational speed falls within the first range or the second range, as adjusted by the hysteresis band, to identify a selected speed range. A switching frequency of a pulse-width modulation signal is varied in accordance with the selected speed range.

Abstract: A method of braking a washing machine from an operational speed to a reduced non-zero speed is provided (as well as a washing machine incorporating the method) for a washing machine driven by one of a synchronous or asynchronous motor. Upon receipt of a speed reduction signal, the motor rotating magnetic fields are collapsed for a defined time period. After the defined time period, DC braking voltage is applied to the motor stator windings at a controlled ramp-up rate to an amplitude to generate a controlled ramped braking torque on the motor until the motor has slowed to a defined reduced speed. Thereafter, the amplitude of the DC braking voltage is set to 0V and the motor is soft started to an amplitude and reduced frequency needed to maintain the defined reduced speed.

Abstract: A controller employed in conjunction with a synchronous generator monitors the output voltage of the generator. The controller employs the monitored output voltage as feedback that is used to control the excitation provided to an exciter field winding. In addition, the controller applies a control loop to the monitored output voltage that detects and modifies voltage ripple signals within the monitored output voltage to generate a compensated signal that is used to control the excitation to the exciter field winding. In particular, by detecting and modifying voltage ripple signals within the monitored output voltage, the controller is able to counteract armature reaction voltage ripples caused by unbalanced short-circuit faults, thereby preventing the build-up of voltage on the DC link.

Abstract: A method and apparatus for stopping an AC motor that is controlling a load while detecting mechanical brake slippage of a mechanical brake for holding the load against movement includes a controller for decreasing torque-producing current commands from the drive while a speed regulator is commanding zero speed, sensing movement of the load while the speed regulator is commanding zero speed, detecting movement of the load past a pre-determined distance limit, and increasing torque to support the load and prevent further movement of the load. The controller will again decrease torque-producing current commands from the drive, and again checking for movement of the load, and upon sensing no load movement upon reaching zero torque, then shutting off the motor.

Abstract: An open-loop system for synchronizing movement of a slide out room includes a pair of motors connected to extendable members which support the room during movement between an extended and a retracted position for driving the extendable members, a controller connected to the motors, and a plurality of switches connected to the controller for permitting operator control of the system. The controller provides synchronized output signals to the motors which have known output characteristics depending upon the motor inputs. The controller thus ensures the motors move substantially in unison without requiring feedback from the motors or the extendable members. The system may be initialized to establish stop positions of the extendable members which are stored in the controller.

Abstract: The present invention relates to a system for controlling the rotation speed of AC motors, in particular single phase motors. In this case, a controllable electronic switching device is connected upstream of the motor and is actuated by a control unit such that a sinusoidal input AC voltage is used to produce a motor AC voltage which can be varied in order to change the rotation speed. The control unit is designed in such a manner that the fundamental frequency and/or the amplitude of the motor AC voltage can be varied by phase gating.

Abstract: A motor control system for controlling the operating speed and direction of a three-phase induction motor. The invention particularly finds use for bringing a rotary printing cylinder precisely into register for processing products in sheet form, such as for printing sheets of corrugated cardboard in a machine for printing corrugated boxes. A three phase induction motor is single phase powered by an AC drive through a first and a second electrical conductor. Direction switching signals and time delay speed switching signals are applied to the appropriate terminals of the AC drive by the second and a third electrical conductor. This allows motor powering and control using only three conductors, such from as the slip rings on industry standard corrugated box printing equipment.

Abstract: A method and apparatus for controlling, in power failure, such a machine that a workpiece and a tool are required to be always synchronized in their motion. The method and apparatus allow the tool and workpiece to move back and stop at a safe area without causing any damage to them when the main power source is lost. When a power failure has happened in the middle of a synchronous operation of the motors (S1), a power regeneration function is first disabled (S2). Then a braking control command is issued so as to decelerate the tool drive motor and the workpiece drive motor while maintaining their synchronization (S3). In this step S3, the deceleration rate is controlled so that the motors regenerates energy just enough for driving the tool feed motor. The tool retracts back to an area where it is no longer engaged with the workpiece, by driving the tool feed motor with the regenerative energy produced by the deceleration of the tool drive motor and the workpiece drive motor (S4).

Abstract: A motor control system for controlling power supplied to an electric motor rotating a rotor employed in a centrifuge is provided. The motor control system includes first, second, and third converters and first and second smoothing capacitors. In a motor power mode, the first converter operates to transfer the charged energy in the first smoothing capacitor to the second smoothing capacitor for providing power to the motor through the third converter, while the second converter transfers, in a motor braking mode, the charged energy in the second smoothing capacitor to the first smoothing capacitor to return the power regenerated by the motor during a braking operation to the AC power supply through the first converter. The second converter performs a function of providing an initial energizing energy to the motor for a given period of time at the start of the braking operation for stability of a power-regenerating operation of the motor.

Abstract: A driver for an induction motor includes a voltage limiter which limits an upper limit value of an output voltage from an invertor circuit in accordance with an output frequency command, a lowest frequency limiter which limits a lower limit of an output frequency from the invertor circuit, a forward rotation limiter which outputs a first power supply interruption signal when the output frequency from the invertor circuit reaches the upper limit, a reverse rotation limiter which outputs a second power supply interruption signal when a reverse rotational speed of the motor reaches a reverse rotation limit level, and a low-speed overload detector which outputs a third power supply interruption signal when a state in which the second power supply interruption signal is not output continues in a low speed abnormality state.

Abstract: The invention is carried out by providing an adjustable frequency power supply connected to an alternating current induction motor which is rotated at speeds in excess of 60 hertz. A plurality of sequential frequency ranges are selected which, together, comprise a total frequency range from a maximum frequency range in excess of 60 hertz to 60 hertz which is applied to the motor. For each frequency range, a maximum breakdown torque of the motor is determined. When it is desired to decrease the speed of the motor, it is decelerated sequentially through each frequency range at a different deceleration rate for each range such that the maximum breakdown torque of the motor within each frequency range is not exceeded. Each different deceleration rate for each frequency range is determined by selecting the minimum period of time, for each frequency range, during which the motor may be decelerated without exceeding the maximum breakdown torque of the motor within that frequency range.

Abstract: A dynamic braking means for a variable speed dynamoelectric eddy current drive consists of an ac motor (4) rotationally coupled through a shaft (6) to an inductor drum assembly (13) of an eddy current coupling (3), where an annular field coil 12 generates an electromagnetic field which couples the inductor drum assembly to a pole assembly (10) which is rotationally coupled to an output shaft (16) which drives an inertial load (20). Upon command to stop and brake, a controller (30) signals a motor switch (26) to disconnect the ac motor from the ac source and connect it to a dc source, causing a braking torque to be produced. Concurrently, the controller signals a coupling switch (28) to go to an open position momentarily until the motor decelerates to approximately zero speed, whereupon the coupling switch is again closed, coupling the inertial load to the motor, thereby providing a braking action.

Abstract: A motor control method and apparatus for a hoist is disclosed in which a drive motor is connected to an adjustable frequency power supply in which the frequency of the power supplied to the motor can be selectively varied. At the initiation of a hoist operation, when the hoist brake is holding the motor and an object constituting a load on the motor stationary, power is supplied to the motor at a predetermined low frequency which is sufficient to provide load holding torque upon release of the brake. The actual current level of the power supplied to the motor is sensed at the initiation of the hoist operation and a signal representative of that current level is compared with a reference signal representative of a current level which is sufficient to provide the load holding torque. If the signal representative of the actual current level of the power supplied to the motor exceeds the reference signal, an output signal is provided which will result in the release of the hoist brake from its holding condition.

Abstract: A control system for an alternating current motor, such as an elevator hoisting induction motor, in response to failure of power supply, such as service interruption, phase open and so forth, performs in a first emergency control mode and in a second emergency control mode. In the first emergency control mode operation, dynamic braking is used to decelerate the motor. On the other hand, in the second emergency mode, triggered while the motor is driven in regeneration mode to recirculate regenerated power to decelerate the motor, a mechanical brake is applied. During second emergency control mode operation, power supply condition is monitored to detect failure of the power supply for switching control mode from the second emergency control mode to the first emergency control mode.

Abstract: There is disclosed a method of controlling a voltage-to-frequency inverter which controls an induction motor by the use of an open-loop system. The motor drives a machine such as a crane, and is braked by a mechanical brake. When the machine is started or stopped, a low-frequency voltage is supplied to the motor so that the motor may produce a torque necessary to hold the load, until the actuation of the mechanical brake ends completely.

Abstract: Here is disclosed an air conditioner comprising a scroll type compressor and a brushless DC motor having a rotor provided with a permanent magnet and a stator provided with a sensor adapted to detect a relative position of said rotor and said stator. Here is additionally disclosed an air conditioner in which the rotor of the brushless DC motor comprises a permanent magnet basically made of rare earth elements inclusive of yttrium, transition metal and boron and a driving circuit for the motor includes a braking circuit adapted to excite coils of the motor to thereby reduce reverse rotation of the rotor.

Abstract: A device for controlling an AC motor for a fork lift truck comprises a detector to detect direction of rotation of an AC motor. The direction of rotation thus detected is compared with a desired direction of rotation of the AC motor, and the AC motor is controlled such that the AC motor operates in a power running mode when the actual direction of rotation of the AC motor is equal to the desired direction of rotation of the AC motor, but it operates in regenerative braking mode when said actual direction of rotation of the AC motor fails to be equal to the desired direction of rotation of the AC motor. The desired direction of rotation of the AC motor may be set manually by an operator or a driver of a vehicle drien by the AC motor.

Abstract: A plurality of speed-sliding compensation amount functions are stored in a sliding compensation amount data memory and one of these functions is selected in response to input of a selection signal. In the selected function, sliding compensation amount data corresponding to the speed of the object of positioning is read out. At least one of current position data and positioning target position data of the object is corrected by the read out sliding compensation amount data. A brake signal is generated on the basis of comparison of the current position data and target position data which have been subjected to this correction and a positioning control of the object is performed by this brake signal. On the other hand, a sliding amount detection circuit is provided for detecting sliding amount of the object from generation of the brake signal until actual stop of the object.

Abstract: An AC induction motor is energized by a voltage fed inverter coupled with a DC power source and is controlled in response to a torque request signal that is provided to accelerate or decelerate the motor as desired to maintain a desired torque output. The motor is operated to have each of a power and brake operation below the base speed of the motor and to have each of a power and brake operation above the base speed of the motor.

Abstract: A control device for supplying current to electrical appliances and particularly appliances having single phase capacitor start motors wherein the control device includes a changeover switch which is mounted between a source of power and the appliance motor and which changeover switch includes selectively operated components for controlling the power supply to the appliance motor or to terminate the power supply thereto. In one embodiment of the invention, a second circuit is provided intermediate the power source and the appliance motor for detecting the amount of current flowing in the circuits so as to insure connection of the starting capacitor of the motor, braking of the single phase motor when power is terminated and to provide an indication of overcurrent in the motor.

Abstract: A dynamic brake control system for an alternating current motor powered by a variable voltage, variable frequency inverter which regulates the speed of the motor. An AC to DC converter converts AC line power to DC power with the DC power being transferred to the inverter via a DC link. During electrical dynamic braking, the inverter functions to transfer power from the motor to the DC link. The torque available to the motor during braking is a function of the receptivity of the DC link. Link receptivity controlled by a resistance connected to the link in which the resistance is modulated at a frequency dependent upon the incoming AC line frequency at the converter. The modulation is binarily controlled so as to minimize ripple current on the DC link without the necessity of providing high frequency control of the modulating electronics.

Abstract: To a controller utilizing thyristors have been added delayed resetting circuits connected to timing circuits for enabling delayed firing, and also circuits for inverting polarity of error signal in order to accommodate regenerative and reverse-plug braking. Other additional circuits include circuits for controlling a ramp generator for developing different segments of a ramp required for different modes of operation of a motor. Sequence switching circuits in the circuits controlling operation of the motor determine that full acceleration or deceleration of a selected mode is completed before a newly selected mode is started.

Abstract: A rotational position, velocity and acceleration of an electrical motor are detected and an amount of overrun produced when the motor has stopped is estimated from the detected velocity and acceleration, and at least one of motor position detection data and a positioning target value is changed in accordance with the estimated amount of overrun. The position detection data and the positioning target value after the change are compared with each other and a command for stopping the motor is generated in accordance with a result of this comparison. A brake is applied to the motor in advance by the amount of the estimated overrun so that the motor is stopped at a desired target position after making overrun. Further, velocity setting signals are generated in accordance with desired acceleration and deceleration characteristics and the velocity control of the motor is effected in an open loop in response to the velocity setting signals.

Abstract: An electronic system is disclosed for controlling both the ascendant and the descendant speed in vertical machines such as cranes, elevators, etc., in which it is required to lift different loads in a regulated and self-controlled manner, laying aside the traditional mechanical and/or pneumatic control systems. Such control is achieved by virtue of the voltages included in the secondary of the motors of the wound rotor type used in such machines to lift or to bring down different loads, which may vary within a wide range from practically the vacuum to an overload, being possible by such control to select and to maintain both the ascendant and the descendant speed of the load.

Abstract: A method for D.C. braking a three-phase asynchronous machine and a circuit arrangement useful in implementing the method. For braking, the first and third stator windings are separated from their phases and a pulsating direct current is caused to flow from the second phase to the first phase via a closed second switch and a diode. The third winding is short-circuited by a third switch which is connected in a loop with a current transformer; the loop carries a current induced by the turning rotor. A signal from the current transformer flows, via a limit indicator, to a digital logic member (OR). When the motor stops, short-circuit current flow is no longer detected, the second switch is opened and the circuit for producing direct current is automatically disconnected.

Abstract: A hybrid electrical braking method and system are provided for tool equipment having induction motor drives. This hybrid electrical braking can be used to advantage in various types of induction motor driven tool equipment where it is desirable rapidly to stop rotation of the motor rotor and tool, whenever the motor is turned off, for example in food processors of the type having a working bowl mounted on a base containing the induction motor, with tool drive means in the bowl for removably supporting a rotary food processing tool driven by the induction motor. The new electrical braking rapidly halts coasting of the rotor and tool by utilizing in sequence two different electromagnetic braking processes, producing rapid but gentle braking effect after the motor has been turned off.

Abstract: The motor braking circuit for use with an alternating current motor and an AC power source includes a power circuit for supplying a DC braking current to the AC motor and a motor speed sensor which causes a mechanical brake to engage the AC motor and its load when the motor speed decreases to a predetermined value. The DC braking current is applied to start the electrical braking cycle as soon as the AC source is disconnected from the AC motor. The RPM sensor monitors the speed of the AC motor during the electronic braking cycle and causes the mechanical brake to engage the motor and its load when the motor speed decreases to a predetermined value to complete the stopping sequence. The AC motor braking system can be installed without any additional direct wiring or additional hardware to the AC motor.

Abstract: Operational control system for lift and elevator machinery adapted for electrodynamic braking, said operational control system being adapted to be connected to the machinery of existing lift or elevator equipment. The operational control system is designed for one-speed A.C. synchronous motors of the short-circuit type forming part of operational control units provided with a simple mechanical brake. The operational control system improves the stop-plane exactitude and reduces brake wear. In the operational control system electrodynamic and mechanical braking is combined, the control being performed via a reference voltage formed from an output signal received from a speed-sensing member.

Abstract: A reciprocating drive system moves a body of defined inertia, such as a carriage supporting electrostatic spraying means, at full speed between two points at which the direction of movement is reversed. The drive system includes an electric motor with polyphase stator windings and a squirrel cage rotor. Transducers responsive to the arrival of the moving body at the aforementioned points produce output signals controlling a phase switching system which reverses the direction of rotation of the motor. Reversal of the motor torque reverses the direction of movement of the moving body within a given travel and within a given time interval to full speed in the opposite direction. A stator current limiter provides positive coupling in an operative condition and no coupling in an inoperative condition with the motor running at full speed. The motor is selected so that the inertia of its rotor closely matches that of the moving body.

Abstract: The motor braking system for use with an alternating current motor and an AC power source includes a power circuit for supplying a DC braking current to the motor. A capacitor which was charged during motor operation, discharges when the motor is turned off and thus provides a pulse of energizing current to a contactor which quickly connects the power circuit to the motor and starts the electric braking cycle as soon as the AC source is disconnected from the motor. A timing circuit is also started and maintains the energizing current for a predetermined amount of time while the motor is coming to a stop. A mechanical brake may also be used to complete the stopping sequence if desired, with the mechanical brake being engaged when the braking current is terminated.

Abstract: A controlled current inverter motor control system including a controlled source of direct current for supplying a variable frequency inverter by way of a direct current link circuit which includes, within the link circuit, a selectively insertable dynamic braking resistive element. Upon a call for a dynamic braking mode of operation, the source of direct current is short circuited and the normal operational or running control of the motor is discontinued. Special circuitry is provided which then forces a special frequency control of the inverter to thus control the angle between the motor flux and motor current to a prescribed value proportional to the extant value of a motor operating parameter (motor current or motor flux) prior to the insertion of the dynamic braking resistive element into the link circuit.

Abstract: An electric brake motor, particularly of the kind having a squirrel cage rotor and a slow-running stator winding with a large number of poles, is provided with electrical switching means to increase the motor current briefly on starting, at least on starting of the slowrunning winding, so as to increase the magnetic field generated by the motor current for releasing the brake. The switching means may be contacts actuated by axial movement of the rotor on starting, or a relay or contactor operated by the motor current or by a control switch. The increase in current may be achieved by briefly shortcircuiting part of the motor winding or by briefly connecting a second, fast-running stator winding in parallel with the slow-running winding in the case of a change-pole motor.

Abstract: The control system has application to polyphase AC wound rotor motor which employ opposed parallel connected phase controlled thyristors together with series connected fixed resistors in each leg of a delta connected secondary impedance network. The line-to-line secondary terminals of the motor provide a source of polyphase variable frequency and variable amplitude AC reference signals. The variable frequency, variable voltage reference signals are converted into complementary pairs of square wave synchronization voltages. These same reference voltages are also concurrently integrated during their respective positive and negative half cycles to provide complementary pairs of constant peak amplitude, variable frequency voltages which are combined with associated ones of the aforementioned synchronization voltages to provide synchronization locks.

Abstract: A control system for a commutatorless motor comprises a frequency converter which includes two graetz-connected thyristor converters and D.C. lines interconnecting the converters, between an A.C. motor and an A.C. power supply. Motoring operation and regenerating operation are selectively effected between the motor and the power supply. In switching the operation mode, one of the converters which has been operated in a recitifier operation mode is first switched to an inverter operation mode, and after it has been confirmed that a control voltage to determine a firing angle of the one converter has been shifted to an inverter region, the other convertor is switched to the rectifier operation mode.

Abstract: An improved capacitive braking system is provided for fractional Horsepower induction motors in home appliances, for example in a food processor of the type having a working bowl mounted on a housing containing the induction motor, with a shaft in the bowl for removably supporting a rotary food processing tool to be driven by the induction motor. The new braking system rapidly halts the coasting motion of the motor rotor and tool after the motor has been disconnected from the electric power line. A first switch is provided to control the application of electrical energy to the induction motor for sustained operation, and a second "pulse" switch is provided to control the application of electrical energy to the induction motor for brief surges of momentary operation. The braking system includes a second capacitor which is external to the induction motor and distinct from the starting capacitor normally associated with an induction motor.

Abstract: A controlled current inverter system forms the basis of an a.c. motor drive system for furnishing the motor load with a variable frequency, variable magnitude a.c. current from an inverter which is supplied from a variable d.c. current source by way of a d.c. link including an inductor. Torque is the control parameter employed in the system and the motor speed and torque are controlled through the control of motor flux and motor current, by maintaining a controlled ratio between the direct and quadrature motor currents, through separate control paths to the d.c. source and the inverter. A third control path functioning on the difference between the desired and actual motor flux serves as a modifier to the main control paths to improve overall operation and control. Means associated with the basic control paths provide for dynamic braking of the motor.

Abstract: The present invention relates to an improved dynamic brake effort control apparatus for use with loads such as a transit vehicle, and which provides a better control of and blending of dynamic brake effort and friction brake effort in relation to the vehicle speed for the improved braking control of the transit vehicle.

Abstract: Dynamic response of an a-c induction motor control system including an adjustable frequency and adjustable magnitude power source is made more stable during the transition from a motoring to an electrical braking mode by modifying the system characteristics as a function of rate of change of motor flux and torque magnitude during electrical braking. The control system responds to a torque command signal and a torque feedback signal to generate an error signal which controls the frequency of the excitation supplied to the motor and thus the torque developed by the motor. During electrical braking this error signal is modified as a direct function of the rate of change of motor flux and as an inverse function of the magnitude of torque developed by the motor. During the transition from motoring to electrical braking, when the system tends to be unstable, the rate of change of flux is relatively high while the motor torque is at a relatively low value.

Abstract: A bidirectional triode thyristor is connected to an R phase of a three-phase induction motor through an up contact set and to its S phase through a down contact set. A full-wave rectifier bridge including four diodes is connected across the R and S phases to be enabled during deceleration of the motor. The thyristor is controlled by an R-to-S phase firing circuit responsive to a command acceleration signal during acceleration of the motor and a difference signal between a command deceleration signal and an actual speed signal for the motor during deceleration of the motor.