Abstract: A system includes multiple hybrid energy storage modules (HESMs) configured to accept constant-current DC input power from a main power source. Each HESM has a plurality of outputs configured to sequentially or simultaneously provide both constant-current and constant-voltage output power to multiple loads, the loads comprising steady state, pulsating, or intermittent loads. Each HESM comprises a combined rotating electrical machine-inertial storage module and electro-chemical storage module configured to generate second power that augments or induces first power derived from the main power source, so as to permit constant power draw or constant current draw from the main power source, wherein the output power comprises the first power and the second power.

Abstract: An AC to DC circuit includes a rectifier circuit, a voltage detecting circuit, the current source and the output circuit. The rectifier circuit converts the AC power to pulsating DC. The constant current source provides current to the voltage detection circuit and to the control port of the output circuit. The current passing throughout the constant current source is the sum of the current flowing to the voltage detection circuit and to the output circuit. The voltage detection circuit increases with the instantaneous value of the output voltage of the rectifier circuit, it absorbs more current from the current provided by the constant current source and less current flows from the constant current source to the control port of the output circuit. The output circuit amplifies the current of the control port and outputs it to power the load.

Abstract: A power supply circuit has an input terminal for electrically connecting to an active wire of an AC power supply, an earth terminal for electrically connecting to a neutral or ground wire of the AC power supply, and a voltage decreasing unit. The voltage decreasing unit has an adjustable capacitor unit with adjustable capacitance for decreasing an AC voltage applied to the input terminal and an output terminal for outputting the decreased AC voltage. An electric motor is combined with the power supply circuit to form a motor device.

Abstract: An AC power controller system applies three-phase AC operating power to an induction motor that drives a non-linear mechanical load. A primary low pass filter is connected in series between branch phase conductors and a power controller of the type that uses gate-controlled switching thyristors for controlling power to the motor. KVAR capacitors connected between the power controller and the induction motor phase windings form a secondary low pass filter across the controller output terminals. The primary and secondary low pass filters isolate the power controller and induction motor with respect to spurious noise and harmonics generated by local as well as remote sources, and also improve real power transfer efficiency from the power generating source to the induction motor by transforming the effective impedance of the power source and induction motor load.

Abstract: An apparatus for improving machine drive performance. The apparatus includes a controller configured to control an impedance of a converter. The converter is configured to be electrically coupled to a plurality of first ends of a plurality of windings of a machine. A plurality of second ends of the plurality of windings of the machine are configured to be electrically coupled to a power source.

Abstract: An active reactive induction motor is provided. The motor comprises two sets of three-phase windings. One set of windings carries the active power and is called the power windings. The second set of windings carries the reactive power and is called the flux windings. The power windings carrying the active power provides more power to the induction motor than the flux windings carrying the reactive power. A driver circuit for driving the active reactive induction motor and the corresponding modes of operation is also provided.

Abstract: A power converter controller is operable to control power provided to a load circuit coupled between a first voltage supply terminal and a first switching element by controlling the first switching element and to control power provided to an energy storage element coupled to the first switching element. The energy storage element is operable to provide a power supply. A first control terminal couples to a control input of the first switching element. A first load terminal couples to the first switching element and the charge storing element. A second switching element couples between the first load terminal and a second voltage supply terminal.

Abstract: A ground detector includes a pair of lines, a first series circuit, a reference portion, a second series circuit, and a detection point. The first series circuit connects the lines to each other. The first series circuit includes first capacitors that are connected in series. The reference portion is connected to a portion of the first series circuit between two of the first capacitors for DC insulating the lines from the reference portion. The second series circuit connects the lines to each other. The second series circuit includes second capacitors that are connected in series. The detecting point is provided in the second series circuit. Each of the lines is connected to the detecting point through at least corresponding one of the second capacitors. The ground detector detects a change of impedance between the lines and the reference portion based on a change of potential of the detecting point with respect to potential of the reference portion.

Abstract: A three-phase direct-current motor is controlled by cyclically repeating three first switching states. In each of the three first switching states, one of the three phases of the direct-current motor is periodically switched over between a first and a second input voltage, whereas the two other phases are continuously connected to the first input voltage.

Abstract: A method is provided for operating a converter circuit, in particular a pulse-width modulated frequency converter circuit having a DC voltage intermediate circuit, which controls two or more winding sections of a polyphase dynamo-electrical machine, in particular a three-phase asynchronous motor for a laundry appliance. The method determines one or more parameters of the dynamo-electrical machine, before a rotating field is produced in the dynamo-electrical machine by the converter circuit. The parameters can be used to deduce a variant of the dynamo-electrical machine, and to select open-loop and closed-loop control parameters which are associated with the variant. Likewise, the method allows possible machine faults to be determined by using the parameters.

Abstract: A fan motor is driven under a pulse width modulation (PWM) control. PWM signals to be supplied to a circuit for driving the fan motor are formed from carrier waves having a specified frequency and a duty ratio of the PWM control. Rotational speed of the fan motor is increased by increasing the duty ratio. In a low speed region, the fan motor is driven with a high carrier frequency to suppress driving noises of the fan motor, while it is driven with a low carrier frequency in a high speed region to reduce switching losses in semiconductor elements. The carrier frequency may be continuously decreased when the fan motor speed reaches the high speed region, or it may be stepwise decreased. The low carrier frequency used in the high speed region is set to such a frequency that guarantees a sufficient number of switching times at a maximum speed of the fan motor.

Abstract: A method of conditioning a signal being communicated between a system to be controlled and a controller may include monitoring an actual output signal and conditioning the actual output signal. The method also includes determining the difference between the actual output signal and the condition signal and causing the actual output signal to be filtered based on the relationship between the difference between the actual output signal and the conditioned signal.

Abstract: A motor torque control apparatus and method are disclosed. By adding the value of the compensation voltage which is obtained by proportionally integrating a difference value between the predetermined reference magnetic flux component current value and the actually measured magnetic flux component current value to the q-axis instructing voltage, the magnetic flux component current, that is, the excitation current, can be constantly controlled without excess or shortage. In addition, since the magnetic flux is constantly controlled irrespective of the speed of the motor, a high torque can be generated even at the initial stage of starting of the motor (at the low speed), and thus, the torque of the motor can be smoothly controlled in every operation range from a low speed to a high speed.

Abstract: A control device for an induction motor controlling torque generation of the induction motor with high precision includes a rotation speed detector which detects the rotation speed of the induction motor, a current detector which detects a primary current of the induction motor; an amplifying unit which amplifies deviation between an estimated primary current obtained from a magnetic flux observing device and the primary current obtained from the current detector; a magnetic flux observing device which estimates an estimated secondary magnetic flux and an estimated primary current of the induction motor based upon the rotation speed obtained from the rotation speed detector, the primary voltage of the induction motor and the deviation signal obtained from the amplifying unit, and a control unit which controls a voltage applied to the induction motor based upon the estimated secondary magnetic flux obtained from the magnetic flux observing device.

Abstract: A method for controlling an induction motor using an equivalent circuit model, the equivalent circuit having a real component and an imaginary component, is disclosed. The method instead of measuring a plurality of induction motor parameters, the real and the imaginary component of the induction motor impedance are calculated based on the measured phase currents and voltages. The invention calculates a first control function based on the real component of the induction motor impedance, and a second control function based on the imaginary component of the induction motor impedance, and adjusts the induction motor excitation frequency until the first control function is approximately equal to the second control function. After the excitation frequency is determined, the motor torque is calculated by taking the square of motor voltage in the d-q reference frame.

Abstract: An improved induction motor having at least one capacitive element electrically connected in parallel with and tapped to each phase of a delta- or wye-wound stator winding such that the capacitive elements are alternately charged or discharged during operation, thereby storing energy from and releasing energy to the windings. This alternate energy storage and release assists in controlling the level of magnetic core saturation and increasing motor efficiency under all operating conditions due to reduced hysteresis and eddy current losses. Motor starting or inrush current is also substantially reduced using this arrangement. In one embodiment, variable capacitors and switch elements are used to provide the ability to dynamically “tune” the motor winding for optimal efficiency.

Abstract: The three-phase power controller is provided which has interrupt-controlled phase-gating control with a simple, cost-effective design. The power controller uses of a single microcontroller with only one or two interrupt inputs. This is made possible by forming voltage zero signals, whose flanks are used for interrupt control. Interrupt routines in the executive program of the microcontroller control the times when trigger signals are emitted, exclusively on the basis of the voltage zeroes as information about the three-phase mains system.

Abstract: A variable-speed control apparatus computes the leakage inductance of an AC motor, correctly compensates the leakage inductance, and controls the variable speed of the AC motor. The variable-speed control apparatus has an AC signal generation circuit for generating an AC signal, and obtains a leakage inductance calculation value of the AC motor based on the AC signal and the measured actual current value. The differential value of the summation of a current command value and the AC signal is multiplied by the leakage inductance calculation value to generate a signal for use in compensating the voltage drop caused by the leakage inductance, and added to a voltage command value to cancel the deviation between the actual current value and the M-axis current command value and to obtain the second voltage command value. The second voltage command value is converted into a 3-phase voltage command value and used in controlling the AC motor, and the voltage drop caused by the leakage inductance can be compensated.

Abstract: A commutation control strategy for eliminating torque ripple and noise from a brushless motor which has a plurality of motor phases connected in a bridge, each phase having a top switching device provided between a phase winding and a positive voltage supply and a bottom switching device provided between the phase winding and a less positive voltage supply in which following commutations of the motor, when the current flowing in a first phase is decaying towards zero and the current in a second phase is rising from zero, the switching devices are operative between a state in which the current flowing in the first phase is caused to decay at a first rate, and another state in which the current flowing in the first phase is caused to decay at a second rate which is lower than the first rate so that the rate of decay of the current in the first phase substantially matches the rate of rise of the current in the second phase.

Abstract: An electric current compensation circuit for use with a multiple-phase burshless motor to reduce ripples in the output torque is disclosed. It contains a plurality of electric current compensation loops each for a respective phase winding and each of the electric compensation loops contains: (a) a first input for receiving a line current from the driver; (b) a second input for receiving the compensation current from the motor sensor; (c) a forward rectifying circuit for forwardly rectifying the line current and the compensation current; (d) a reverse rectifying circuit for reversely rectifying the line current and the compensation current; and (e) a summation circuit for summing the forwardly rectified compensation current and the reversely rectified compensation current and outputting a synthetic current to a phase winding of the motor.

Abstract: The invention concerns an improved system for windshield wipers in vehicles. An induction motor is used, in which speed is accurately controlled by controlling frequency of power supplied to the motor. The induction motor may be of the consequent-pole type, which ordinarily does not produce sufficient torque. Addition of (a) auxiliary tooth slotting and (b) skew has raised the torque produced to acceptable levels.The invention includes a control system, which senses excess load on the motor, which occurs as the windshield dries, and reduces motor speed, subject to a minimum, in response.

Abstract: A servo controller for servo-controlling an operative device, the servo controller is provided with an actuator having a motor for actuating the operative device; a sensor for detecting an operational state of the operative device; a comparator for receiving a detected operational state of the operative device from the sensor and comparing the detected operational state with a target operational state to produce a control signal; and a driver provided between the actuator and the comparator for driving the actuator in accordance with the control signal, the driver including a negative impedance circuit with respect to the actuator.

Abstract: A disk drive including firmware for overcoming stiction and breaking free the heads of a disk drive which may adhere to the disk surface when the disk is at rest. Upon start-up of the disk drive, if stiction at the head/disk interface occurs, the voltage to the spindle motor and/or actuator motor may be rapidly fluctuated so as to cause a pulsing of the spindle motor and/or actuator motor. Pulsing both the spindle motor and actuator motor creates forces in a plurality of radial directions to allow the head(s) to break free from the disk(s) in the direction of least resistance. Moreover, as the resonant frequency of the spindle motor varies depending on the number of heads that are stuck, the firmware pulses over a range of frequencies including the various resonant frequencies of the spindle motor corresponding to various numbers of heads stuck.

Abstract: In a motor drive circuit, the collector-emitter paths of two npn-type transistors are connected in series between a power line and ground, and the junction between the two transistors is connected to a motor coil. A control circuit feeds a control current to the base of the transistor connected to the power line so that this transistor supplies a drive current to the motor coil. A current mirror circuit is provided which is constituted of two pnp-type transistors whose emitters are connected to the power line, and the base and collector of the input-side transistor is connected to the control circuit through a diode. The base of another pnp-type transistor is connected to the cathode of the diode, and the emitter of this transistor is connected to the collector of the output-side transistor of the current mirror circuit and to the base of the transistor connected to the power line.

Abstract: A control system (100) for a five-phase brushless DC motor (102) including a stator having five windings and a rotor (116) mounted for rotation relative to the windings (114). The windings (114) are adapted to be electronically commutated in response to the rotary position of the rotor (116). The control system (100) includes a sensing circuit (106) to sense the rotary position of the rotor (116) using an optical or magnetic sensor or the back electromotive force voltages in the windings (114). Electronic switches (112) control the flow of current through the windings (114) in response to control signals generated by a control circuit (110) in response to the rotary position of the rotor (116). The control circuit (110) includes start-up logic to start the motor (102).

Abstract: An improved power supply for converting any of various standard national AC network voltages to low-voltage DC power suitable for driving a 1 or 2-watt device, such as a fan, features a semiconductor control circuit (18, FET 46) which chops each half-wave of a rectified voltage and uses the low-voltage portions to feed charging current pulses to a storage capacitor. The voltage on the capacitor (14) is used by other portions of the circuit to regulate rotation speed of the fan or other consuming device (40) to a value set on a variable resistor. The use of the low-voltage portions of the input signal reduces power losses and increases efficiency.

Abstract: An asynchronous motor is supplied with power from an AC line voltage via a variable speed drive including a rectifier bridge connected to the AC line voltage, a DC voltage intermediate circuit including a capacitor and an inverter including switches and connected to the phase windings of the motor. A system for controlling the power supply to the motor includes a device for controlled resumption of motor speed after supply of power to the motor is interrupted.

Abstract: An air conditioner having a fan motor brown-out control algorithm for increasing the air conditioner fan speed upon sensing a brown-out under-voltage condition is provided. The air conditioner has a power supply connected to an AC line voltage, a fan motor, a multispeed fan driven by the fan motor and means for sensing a brown-out condition of the AC line voltage. The sensing means is connected to the power supply and provides a signal indicative of a brown-out condition. The air conditioner also has means for increasing the speed of the fan in response to the sensed brown-out condition signal provided by the sensing means. In an embodiment, the air conditioner further has a microprocessor and related circuitry for adjusting the speed of the fan. In another embodiment, logic circuitry is provided instead of a microprocessor. A brown-out control algorithm for an appliance having a multispeed fan and components for operating the fan is also provided.

Abstract: A motor speed controller for use with dc motors, such as found in model (slot) cars, is provided by a plurality of pairs of oppositely-poled voltage-sensitive threshold conduction devices which are selectively connected so as to be controllably inserted between a source of operating voltage and the dc motor. In a preferred embodiment of the invention, the voltage-sensitive threshold conduction devices advantageously comprise a series connection of diode bridges which are sequentially included in the energizing path of the motor.Furthermore, the controller provides a speed sensitive brake function by controllably connecting at least one voltage-sensitive threshold conduction device across the windings of the dc motor. When so connected, this allows the voltage generated by the spinning motor to cause the voltage-sensitive threshold conduction device to be conductive until the motor speed slows to the point that the generated voltage no longer causes the device to conduct.

Abstract: A circuit and method for generating drive signals having a frequency synchronized to a reference frequency signal is disclosed. The circuit includes a PLL that includes a motor, and a circuit for generating a signal having a frequency proportional to the speed of the motor. A phase detector produces a signal for a time proportional to a phase difference between the motor speed signal and a reference frequency signal. A first phase difference measuring circuit produces a first voltage output signal at a first gain proportional to the phase difference when the duration of the phase detector signal is less than a predetermined time. A second phase difference measuring circuit produces a second output signal at a second gain when the duration of the phase detector signal is greater than the predetermined time. The first and second output signals are summed and applied to control the speed of the motor.

Abstract: An energy conserving device which reduces excess level of alternating current power fed to RUN windings of an a.c. electric induction motor whenever the motor is less than fully loaded. A voltage dropping reactor coupled between an a.c. power source and the motor produces about 10-30% reduction in applied motor terminal voltage under reduced motor load running conditions, while a semiconductor switch acts to instantly shunt out the voltage dropping effect of the reactor and couple an increased portion, or full level of a.c. terminal voltage to the motor whenever the motor load increases. Changes in instantaneous levels of motor loading may be determined by changes in motor speed slip, determined from the motor's operating power factor, or preprogrammed. As a result of less a.c.

Abstract: A motor having a capacitor in series with its coil permits the motor to operate at a higher voltage or range of voltages over its design voltage. A method determines the correct value of a capacitor to change the design voltage of a motor to a different operating voltage. A receptacle can be used to receive capacitors of different values to vary the operating voltage of a motor. The receptacle is provided with a capacitor holding device which is marked with the operating voltage set by the capacitor. A timer clock has a motor of a design voltage which can be changed to a plurality of operating voltages. The timer clock can have the receptacle accessible from the exterior with a cover having the operating voltage marked thereon.

Abstract: This invention relates to motor speed control circuits employing capacitors. Two windings of a motor are connected in parallel to a neutral phase of an alternating current source. Each coil of the motor may be connected to the live phase of the source whereby the rotation direction of the motor may be altered. Three socket terminals are connected to each winding. A capacitor pack has three pins with two capacitors connected between a common pin and the two remaining pins. The pins of the capacitor pack can be inserted into the sockets in three different ways whereby either capacitor or the two capacitors in parallel can be connected across the windings to vary thereby the speed and performance characteristics of the motor.

Abstract: A warming fan with a speed reducing device comprises a choke coil which connects with the running inductor of the power set of the warming fan, a diode which is paralleled to the choke coil and a choke coil which is paralleled to the above-mentioned choke coil and connected in series with the diode in the downstream of the same. The warming fan can keep its revolution speed low enough and keep its revolution torque high enough, because the power set of the warming fan is driven by a relatively high voltage corresponding to its revolution speed, but which is interrupted intermittently.

Abstract: A switching arrangement for delivering power to an A. C. induction motor having a running winding and a start winding. A single-pole or double-pole, double-throw switch is provided for reversing current flow in the running winding is provided to reverse the rotational direction of the motor. A first four-position switch and a second four-position switch are operatively arranged to connect a first capacitor, a second capacitor and a resistor in three different circuit configurations with the windings across an A. C. power supply so as to provide three different rotational speeds under a given load. In a fourth position, the first and the second four-position switches effect a disconnection of the motor from the A. C. power supply.

Abstract: A compact, high efficiency non-interruptive motor generator power system for generating and supplying to a load A.C. of a substantially constant frequency and of a substantially constant voltage, the motor thereof being a synchronous A.C. motor energizable from a source of irregular and interruptible A.C. line power, the generator being capable of converting its rotational energy into the A.C. output for many seconds after interruption of the A.C. line power. The power system comprises a high efficiency, synchronous permanent magnet A.C. motor and an A.C. generator coupled to and driven by the motor. Both the motor and generator have a high rotational enertia common rotor wherein an outer cylindrical shell contains motor and generator rotor elements of high permeability soft magnetic material with a surface layer of magnetizable permanent magnetic material, and in each stator is an excitation coil, energizable with A.C.

Abstract: A remote speed controller for an electric motor, the controller comprising a switching unit having three switches. A capacitor pack incorporating two capacitors is connected to the switching unit such that different combinations of the capacitors can be selected by one switch. The controller is connected in circuit between an AC voltage supply and windings of a motor so that selective actuation of the one switch changes the speed of the motor in accordance with the values of the capacitors selected. Further switches are incorporated to provide reverse motor capability and remote sensor capability.

Abstract: A system for controlling the operation of an alternating current induction motor having windings supplied by electrical power from the polyphase alternating current source includes a load commutated inverter circuit which is connected between the power source and the induction motor for furnishing electrical power to the motor. Controllers responsive to a command signal and a feedback signal indicative of motor operating parameters control the operation of said load commutated inverter circuit. There is further provided a fixed capacitor circuit connected between the windings of the motor for supplying reactive volt amperes (VARs) to said load commutated inverter circuit and said motor.

Abstract: A system for controlling the operation of an alternating current induction motor having windings supplied by electrical power from the polyphase alternating current source includes a load commutated inverter circuit which is connected between the power source and the induction motor for furnishing electrical power to the motor. Controllers responsive to a command signal and a feedback signal indicative of motor operating parameters control the operation of said load commutated inverter circuit. There is further provided a fixed capacitor circuit connected between the windings of the motor for supplying reactive volt amperes (VARs) to said load commutated inverter circuit and said motor.

Abstract: An alternating current motor drive in which the motor is furnished with electrical excitation from an alternating current source through a controllable power converter also includes first and second capacitor circuits connected to the common point between the converter and the motor. The first capacitor circuit is connected to the common point through an isolating inductor circuit. The second capacitor circuit is connected to the common point via the parallel combination of an inductor circuit and a resistor circuit. A further embodiment includes a variable VAR generator connected to the junction of the second capacitor circuit and the parallel combination of the inductor and resistor circuits.

Abstract: A system for controlling the operation of an alternating current induction motor having windings supplied by electrical power from the polyphase alternating current source includes a load commutated inverter circuit which is connected between the power source and the induction motor for furnishing electrical power to the motor. Controllers responsive to a command signal and a feedback signal indicative of motor operating parameters control the operation of said load commutated inverter circuit. There is further provided a fixed capacitor circuit connected between the windings of the motor for supplying reactive volt ampheres (VARs) to said load commutated inverter circuit and said motor.

Abstract: A system for controlling the operation of an alternating current induction motor having windings supplied by electrical power from the polyphase alternating current source includes a load commutated inverter circuit which is connected between the power source and the induction motor for furnishing electrical power to the motor. Controllers responsive to a command signal and a feedback signal indicative of motor operating parameters control the operation of said load commutated inverter circuit. There is further provided a fixed capacitor circuit connected between the windings of the motor for supplying reactive volt amperes (VARs) to said load commutated inverter circuit and said motor.

Abstract: A synchronous A.C. electrical motor comprising (A) a stator having a body of slotted, soft ferromagnetic, low eddy current loss material, the slots having A.C. power windings to produce a rotating magnetic field, an excitation coil energizable with single phase A.C. located in two adjacent slots with a pole piece between them, and feedback windings located in slots such that when A.C. potential therefrom is conveyed to the excitation coil the excitation A.C.

Abstract: A squirrel-cage induction motor comprises a stator having a stator core and stator windings divided into first and second coils with different numbers of poles, and a squirrel-cage rotor including a rotor core and a plurality of rotor conductors embedded in the vicinity of the surface of the core. The number of the rotor conductors is the same as the average number of poles of the first and second stator coils, which conductors are arranged equidistantly along the periphery. This induction motor, with the construction of a squirrel-cage rotor, permits a variable speed operation without using any special device.

Abstract: An electrotechnical regulating device for asynchronous rotating machines comprises capacitors in series with the windings of the asynchronous motor. In order to regulate the speed of rotation of an asynchronous motor, the device further comprises a variable-impedance short-circuiter connected in parallel between at least one of the windings and the associated capacitor or capacitors. The device serves to modify the torque of an asynchronous motor supplied at a variable frequency and at a fixed voltage, in order to control the speed of an asynchronous motor which is supplied at fixed or variable frequency or in order to regulate the voltage of an induction generator which rotates at a fixed or variable speed.

Abstract: In order to minimize the current consumption of an alternating-current motor of the induction or the synchronous type (or possibly a plurality of such motors connected in parallel) driving a variable load, a sensor coupled to a supply line of the motor detects the occurrence of a significant change in its operating current and determines the sense of that change. A controller responsive to signals from the sensor then reduces the supply voltage by an incremental or decremental step and, if the sensor detects a resulting decrease in amperage, continues with one or more similar steps until the current levels off. If the initial voltage modification causes the current to rise, the controller progressively changes the supply voltage in the opposite sense until the amperage reaches a minimum.

Abstract: An induction motor comprises a main winding (41) and an auxiliary winding (42) wound in slots of a stator with proper intervals, the main winding (41) and the auxiliary winding (42) being connected to an alternating current voltage source (1) through a conduction control circuit (20). A control winding (9) is electromagnetically coupled to the main winding (41), with the same shunted by a capacitor (10) so that a closed loop may be formed.

Abstract: In a polyphase machine, being either a motor or a generator, there is provided a stator core having main stator windings wound about the stator core and main windings having a capacitor connected in series with each winding of the core. Switches are provided for each winding, and a trigger source for the switches operates with the capacitor and windings to ensure sequential current flow in opposite directions across the windings. Variable frequency pulses from a trigger results in a variable speed machine. With control windings wound on the stator, oppositely to the main windings there are currents in each phase which are substantially in-phase at no load with the currents of the corresponding radially adjacent the main windings. Such currents become out of phase with their main winding currents as the load increases. At low load the net flux density is low and as the load increases the flux density increases.

Abstract: The voltage and frequency of an A.C. excitation signal applied to the stator windings of an A.C. induction motor are varied in proportion to the amplitude of current flowing in the stator windings. The stator current flow is sensed by a feedback resistor in series with the inverter which generates the A.C. excitation signal for the stator windings. The voltage drop aross the feedback resistor is summed with a VELOCITY COMMAND voltage which indicates the desired speed of the motor and the summed voltage controls the frequency and the amplitude of the A.C. excitation voltage in a constant volts per hertz manner. The stator current feedback holds the motor speed constant in spite of variations in the load on the motor.

Abstract: This invention is directed to a controllable infinitely variable speed A.C. electrical motor, comprising a rotor having a core of soft magnetic material carrying a peripheral layer of magnetizable permanent magnet material, which layer is magnetized by a stationary excitation coil energized with A.C. potential so that the peripheral layer assumes a selected configuration of north and south magnetic poles as the rotor revolves; A.C. potential is also applied to windings in slots in the stator core to provide a plurality of magnetic poles in the stator coacting magnetically with the configuration of north and south magnetic poles in the layer of magnetic material in the rotor, whereby to cause the rotor to revolve. Phase shifting means are provided in the circuit leading to the excitation coil to enable the phase of the A.C. current being supplied thereto to be shifted with respect to the phases of the A.C.