Abstract: In a power converter for converting DC power from a DC power source into AC power and supplying the AC power to a single-phase winding or multi-phase windings, a controller controls first and second inverter circuits and performs first power conversion control to lock open/closed states of switching elements in the second inverter circuit and switch open/closed states of switching elements in the first inverter circuit, and second power conversion control to lock open/closed states of the switching elements in the first inverter circuit and switch open/closed states of the switching elements in the second inverter circuit. The controller is configured to perform either the first power conversion control or the second power conversion control when an effective value of drive current through each winding is less than a threshold, and otherwise switch between the first power conversion control and the second power conversion control.

Abstract: A control device of a vehicle includes a controller performing overheat protection control on parts, distinguish first, second, and third parts groups among the parts of the vehicle, set only the first and the third parts group as protection targets in a charging mode while the vehicle stops, set only the second and the third parts group as the protection targets when the vehicle is in a mode other than the charging mode while the vehicle is running, and not to perform the overheat protection control when the vehicle is in a mode other than the charging mode while the vehicle stops.

Abstract: The present disclosure discloses a multilevel inverter configured to output a 3-phase voltage to a motor by allowing a plurality of unit power cells forming one phase to be serially connected, the multilevel inverter, the multilevel inverter including a plurality of current sensors configured to detect an output current of the plurality of unit power cells.

Abstract: To provide a three-level power conversion apparatus which can suppress fluctuation in a neutral point voltage even when operated as a reactive power regulator. The three-level power conversion apparatus is composed of first and second three-level converters 2A, 2B connected to an AC power supply system, positive side and negative side DC capacitors 3P, 3N, a three-level inverter 4 to drive an AC motor 5, and converter control means 10 for controlling the three-level converters 2A, 2B.

Abstract: A control device for a railway vehicle controls an inverter device based on a direct-current link voltage Vfc between the opposite terminals of a filter capacitor. A direct-current voltage applied to the inverter device during regeneration is the sum of a voltage Vb of power storage equipment and an overhead wire voltage Vs, so that only detecting the direct-current link voltage Vfc is not enough to separate the voltage Vb of the power storage equipment and the overhead wire voltage Vs from each other. The power storage equipment can be connected in series with the inverter device, and a voltage sensor that detects the overhead wire voltage Vs is provided between a current collector device and a grounding point. The power storage equipment is controlled based on the detection result from the voltage sensor.

Abstract: A control circuit for a fan includes a fan controller, a switch controller, and a frequency detector. When a pulse-width modulation (PWM) signal output pin of the fan controller outputs PWM signals, the frequency detector outputs a high level signal, connecting an input pin of the switch controller to an output pin of the switch controller. The fan receives the PWM signal. When the PWM signal output pin of the fan controller does not output PWM signals, the frequency detector outputs a low level signal, such that the output pin of the switch controller does not output any signal. In this state, the fan receives a high level signal through a resistor and a power supply, enabling the fan to continue operating.

Abstract: An electronic device includes a first control circuit which controls a first drive circuit to drive a cooling device, a second control circuit which controls the first drive circuit, a switch circuit which connects one of the first and second control circuits to the first drive circuit, and a switch control unit which controls the switch circuit when there occurs a fault on the first control circuit, and switches a connection target of the first drive circuit from the first control circuit to the second control circuit.

Abstract: Apparatus and method for reducing current drain and current spike impact on a dispenser electric motor by employing a series of supercapacitors in a power supply current to provide at least a portion of the energy requirement of the dispenser electric motor upon initial energization.

Abstract: A method and arrangement in connection with an electric drive system are provided. The electric drive system includes an intermediate circuit with two or more supply units and two or more inverter units connected thereto, and an electric machine having two or more three-phase windings galvanically separated from each other. Two or more inverter units are connected to the three-phase windings. The arrangement also includes first main circuit switches to galvanically separate each supply unit from a supply, second main circuit switches to galvanically separate each supply unit from the intermediate circuit, first intermediate circuit switches to galvanically separate each inverter unit from the intermediate circuit, and second intermediate circuit switches to galvanically separate each inverter unit from the electric machine.

Abstract: A method for testing rotation speed of a fan receives a duty cycle ratio related to the fan sent from a dial switch on a test board connected to the fan. The method transmits a pulse width modulation (PWM) signal based on the duty cycle to the fan to power rotation of the fan, then detects the PWM signal transmitted to the fan and a tachometer (TACH) signal transmitted from the fan. The method gathers the duty cycle ratio related to the fan from the PWM signal and an actual rotation speed of the fan from the TACH signal, and displays the duty cycle ratio and the actual rotation speed together on the test board.

Abstract: A method, system and computer program product for monitoring health of a synchronous machine is provided. The method includes receiving a plurality of phase voltage values and a plurality of phase current values. The method then computes a negative sequence voltage (Vn) based on the plurality of phase voltage values. The method also computes one or more operating parameters based on at least one of the plurality of phase voltage values and the plurality of phase current values. The method retrieves from a data store, one or more known Vn based on the one or more operating parameters. The method then computes a machine health indicator based on the computed Vn and the one or more known Vn, and raises an alarm based on the machine health indicator.

Abstract: The present invention relates to a motor assembly, a method of operation thereof and a transport vehicle provided with the motor assembly. The motor assembly is provided with an energy source switching controller that is in synchronization with motor operation and provides an improved utilization of energy storage sources in an electric, hybrid electric, or fuel cell based motor vehicle drive train application.

Abstract: An electric drive system includes an energy storage system (ESS), a power conversion system, and an alternating current (AC) traction system. The ESS provides or receives electric power. The ESS includes a first energy storage unit and a second energy storage unit. The power conversion system is electrically coupled to the ESS for converting an input power to an output power. The AC traction system is electrically coupled to the power conversion system for converting the output power of the power conversion system to mechanical torques. The AC traction system includes a first AC drive device and a second AC drive device. An energy management system (EMS) is in electrical communication with the ESS, the AC traction system, and the power conversion system for providing control signals.

Abstract: This invention relates to a multiple phase electrical system, including: a first and a second electrical lane, each lane having a generator and a load connected by a bus system, and a rectifier between the generator and load; and, a transformer connected between the two lanes, the transformer having a plurality of power windings across each of which corresponding phases of the first and second lanes are connected, and a plurality of phase shift windings.

Abstract: A fuel cell system (10) includes: a motor (16); a fuel cell (11) and an electrical storage device (13) connected to the motor (16) in parallel with each other; a first voltage converter (12) between the motor (16) and the fuel cell (11); a second voltage converter (14) between the motor (16) and the electrical storage device (13); a load circuit between the motor (16) and both the first (12) and second (14) voltage converters; and a control unit (20). The control unit (20) stops boost operation of the first voltage converter (12) when conditions VFC>VM_min and VFC>VBAT+a whereas the control unit (20) prohibits a stop of the boost operation of the first voltage converter (12) when the conditions are not satisfied, wherein in the conditions, VFC is a fuel cell terminal voltage, VBAT is an electrical storage device terminal voltage and VM_min is a load circuit input terminal voltage, set to minimize a system loss while ensuring a torque required of the motor (16).

Abstract: Provided is an inverter-integrated electric compressor having high heat resistance, which is capable of suppressing thermal interference among a plurality of power devices. Specifically provided is an inverter-integrated electric compressor which comprises a built-in motor and a substrate provided with a motor drive circuit including an inverter, an electric component including the substrate being affixed in a housing space surrounded by a compressor housing, wherein a plurality of power semiconductor elements which constitute the motor drive circuit are disposed radially around a drive shaft of the motor in a plane crossing the drive shaft. For example, the planar shape of the power semiconductor element is formed into a rectangle, and a gap having a sectorial planar shape is formed between the power semiconductor elements adjacent to each other.

Abstract: A control circuit for a fan includes a fan controller, a switch controller, and a frequency detector. When a pulse-width modulation (PWM) signal output pin of the fan controller outputs PWM signals, the frequency detector outputs a high level signal, connecting an input pin of the switch controller to an output pin of the switch controller. The fan receives the PWM signal. When the PWM signal output pin of the fan controller does not output PWM signals, the frequency detector outputs a low level signal, such that the output pin of the switch controller does not output any signal. In this state, the fan receives a high level signal through a resistor and a power supply, enabling the fan to continue operating.

Abstract: A control device of an electric power supply apparatus controls a voltage applied to an inverter to fall within a voltage range between a first voltage that is the voltage of one of a first electric power supply and a second electric power supply and a second voltage that is the sum of the voltage of the first electric power supply and the voltage of the second electric power supply, by alternately switching between a series state in which a current loop that connects the first electric power supply, the second electric power supply, and a reactor in series with the inverter is formed, and a parallel state in which the first electric power supply and the second electric power supply are connected in parallel with the inverter as an electric load.

Abstract: A drive circuit comprising a DC bus configured to supply power to a load, a first fuel cell coupled to the DC bus and configured to provide a first power output to the DC bus, and a second fuel cell coupled to the DC bus and configured to provide a second power output to the DC bus supplemental to the first fuel cell. The drive circuit further includes an energy storage device coupled to the DC bus and configured to receive energy from the DC bus when a combined output of the first and second fuel cells is greater than a power demand from a load, and provide energy to the DC bus when the combined output of the first and second fuel cells is less than the power demand from the load.

Abstract: The present invention relates to an electric device for driving mechanical equipment comprising an alternating current motor and an inverter, the said inverter comprising, for each phase of the said motor, an H bridge structure comprising four switching elements distributed over two branches connecting two terminals of the said H bridge structure and intended to supply the winding of the said at least one phase of the motor, the said winding being a winding with a mid point and the said electric device being characterized in that it also comprises, for each phase of the said motor, an energy storage unit, in particular a supercondenser, connected, on the one hand, to the mid point of the winding of the concerned phase of the motor and, on the other hand, to a terminal of the H bridge structure supplying the said winding.

Abstract: A control device for a railway vehicle controls an inverter device based on a direct-current link voltage Vfc between the opposite terminals of a filter capacitor. A direct-current voltage applied to the inverter device during regeneration is the sum of a voltage Vb of power storage equipment and an overhead wire voltage Vs, so that only detecting the direct-current link voltage Vfc is not enough to separate the voltage Vb of the power storage equipment and the overhead wire voltage Vs from each other. The power storage equipment can be connected in series with the inverter device, and a voltage sensor that detects the overhead wire voltage Vs is provided between a current collector device and a grounding point. The power storage equipment is controlled based on the detection result from the voltage sensor.

Abstract: There is provided a method of detecting a stop of a transport apparatus which can quickly and easily detect and improve the throughput and the ratio of utilization without incurring an increase the number of parts. The apparatus is used which is provided with a drive motor and a transport arm one side of which is mounted on a rotary shaft of the drive motor. As the drive motor there is used one in which an induced electromotive force is generated when a force in the direction of rotation is applied to the rotary shaft. Then, an article S to be transported is held on the other side of the transport arm. When the drive motor is operated to drive the rotary shaft by a predetermined angle of rotation and then stopped, the above-described induced electromotive force to be generated due to the vibrations of the transport arm is detected.

Abstract: Power conversion equipment includes an electric power converting section that converts DC electric power to multiphase AC electric power and feeds the converted multiphase AC electric power to a multiphase AC motor. A first short-circuit section includes a first switch disposed between a first DC power supply and the electric power converting section. A second short-circuit section includes a second switch disposed between at least one of an electric power feeding section and the electric power input section in the first DC power supply, or between a multiphase AC output point of the electric power converting section and the multiphase AC motor. A switch control section controls the first switch and the second switch such that the first and second switches are prevented from being brought into the closed-state simultaneously.

Abstract: A control system and method for a multi-phase motor substantially reduces or eliminates jitter resulting from drive mismatch by replacing a conventional trapezoidal drive profile with a drive profile that causes the voltage applied across active phases of the motor to match the back-EMF across those phases. In an ideal motor, the back-EMF is substantially sinusoidal, and although the drive profile applied to each phase is not truly substantially sinusoidal, the drive voltage across the active phases is substantially sinusoidal. In a non-ideal motor, the back-EMF is not truly sinusoidal and the drive profiles applied to each phase are calculated to cause the drive voltage across the active phases to match the back-EMF across those phases.

Abstract: Methods, system and apparatus are provided for increasing voltage utilization in a five-phase vector controlled machine drive system that employs third harmonic current injection to increase torque and power output by a five-phase machine. To do so, a fundamental current angle of a fundamental current vector is optimized for each particular torque-speed of operating point of the five-phase machine.

Abstract: A controller for managing electrical power storage in a machine having an electric energy storage device and an electric motor comprises a gate drive stage for providing gate signals to one or more power electronics elements, as well as a control processor adapted to generate gate signals and supply the generated gate signals to the gate drive stage for controlling the one or more power electronics elements. The gate signals control the one or more power electronics elements to power the motor windings in a drive mode of operation and to charge the electric energy storage device in a charging mode of operation. In either mode, the motor windings are used as conductors or inductive elements.

Abstract: Control circuitry for inductive loads comprehending a DC power source (DC), electrical switches (A and R) and appropriate electrical conductors to direct current to an inductive load, as the control system includes a primary circuit and a secondary circuit which is partly concurrent with the primary electrical circuit. The primary electrical circuit includes a series of DC power sources (DC), an inductive load in the form of an electric motor (M) or transformer (T) and a capacitor (C), while the secondary electrical circuit includes the inductive loads and capacitor (C), since the two electrical switches (A and R) are so arranged that the power of a first operational phase is driven through the primary electric circuit by the voltage supplied by the DC power source (DC) while the current in another phase of operation runs through the secondary electric circuit by the voltage supplied by the capacitor (C).

Abstract: A safety drive unit (1) with a safety circuit (12) that resets a flap or a valve into a specified safety position for controlling a gas or liquid volumetric flow, in particular in the field of heating, ventilation, and monitoring systems. The safety drive unit (1) comprises an actuator (14) with a controllable electric motor (28), a capacitive energy storage unit (20), and energy converter (22) with a power module, and a power supply (18). During normal operation, the electric current in the power module of the energy converter (22) is converted to a lower voltage and stored in the capacitive energy storage unit. If the voltage drops below a predetermined value or if there is a power failure, the stored electrical charge is converted back to a higher voltage by the same power module, and the electric motor (28) is activated until the specified safety position is reached.

Abstract: The invention relates to electric engineering, in particular to methods for controlling an ac electronic motor. The inventive control method consists in starting and rotating a rotor upon EMF signals in current-free sections of an armature winding, in converting the EMF signals into discrete logical level signals by a normalizer, in detecting switching points by means of a microcontroller and in displacing said points according to a load current quantity, the rotor speed of rotation and the inductance of the armature winding sections, wherein the switching points are calculated and displaced with respect to bridging times of the free sections EMF whose voltage levels are different from zero. The inventive device is characterized in that it comprises a reference level displacing unit (26), which is arranged in the normalizer between a divider 22 and a comparator unit (23) and which consists of a current sensor (27), a voltage sensor (27), two adders (29, 30) and an inverter (31).

Abstract: A method and arrangement in connection with an electric drive system are provided. The electric drive system includes an intermediate circuit with two or more supply units and two or more inverter units connected thereto, and an electric machine having two or more three-phase windings galvanically separated from each other. Two or more inverter units are connected to the three-phase windings. The arrangement also includes first main circuit switches to galvanically separate each supply unit from a supply, second main circuit switches to galvanically separate each supply unit from the intermediate circuit, first intermediate circuit switches to galvanically separate each inverter unit from the intermediate circuit, and second intermediate circuit switches to galvanically separate each inverter unit from the electric machine.

Abstract: An electric drive which has an inductor with poles, an armature having a plurality of windings and rotatable relative to the inductor and its poles, and a control unit which, when a respective one of the windings of the armature approaches a respective one of the poles of the inductor, turns off a voltage supply to the winding so that when the winding passes the pole it does not have a voltage, and when the winding moves away from the pole the control unit supplies opposite voltage to the winding, and therefore no counter electric motive force is generated during the operation of the electric drive.

Abstract: The present invention relates to energy saving electronic device, a heat dissipating fan power control system and a control method thereof. The heat dissipating fan power control system comprises a voltage selection circuit and a voltage conversion circuit. A plurality of voltage signals from a plurality power input terminals and a control are received by the voltage selection circuit to select one of the voltage signals as an output voltage signal. The voltage conversion circuit is connected to the voltage selection circuit to receive the output voltage signal and the control signal and to convert the voltage value of the output voltage into the work voltage value according to the control signal to thereby drive the heat dissipating fan.

Abstract: A feed motor lock detection device detects a back-electromotive voltage in a feed motor M and checks whether the feed motor M is in a driven state or in a non-driven state based on the level of the back-electromotive voltage.

Abstract: A submersible motor is provided for a submersible pump, the motor being configured as a single-phase asynchronous motor, which includes a main winding (6), an auxiliary winding (8), and a starting device (10, 14, 16, 18, 20, 22) for controlling the starting procedure of the submersible motor. The starting device (10, 14, 16, 20, 22) for the control of the current feed of the auxiliary winding (8) includes at least one electronic switch (20) in the circuit of the auxiliary winding (8).

Abstract: Energy recovery during recirculation phases of the phase windings of a multiphase spindle motor is increased when all the MOSFETs of the output bridge stage associated therewith are turned off (tristated) for charging a hold capacitor. This is accomplished by allowing the recirculation of the motor currents through the same MOSFETs of the output bridge stage that are turned on during the current recirculation phases. Recirculation of the currents and the charging of the hold capacitor takes place through fully saturated power MOSFETs.

Abstract: A method and system for providing sensorless brushless DC motor control using predictive switch timing requires connecting a stator coil in a bridge configuration, applying a positive excitation voltage across the coil for a predetermined time period, deactivating the excitation voltage, and monitoring the voltage (VEMF) generated due to electro-motive force (EMF) across the coil. The polarity of VEMF changes when the rotor has moved a known distance—typically 90°. After detecting a polarity change, a negative excitation voltage is applied across the coil, deactivated, and VEMF monitored to detect a polarity change. This sequence is repeated to maintain the rotation of the rotor. The motor is preferably set into motion using a start-up routine, which also determines the predetermined time period used during steady-state operation.

Abstract: Disclosed herein is a control method of a sensorless brushless direct current (BLDC) motor, and more particularly, a drive control method of a concentrated winding BLDC motor which prevents shutdown due to failures of detection of zero cross points (ZCPs). A reference voltage inputted to comparators is altered to set new reference points. ZCPs are detected using the new reference points to avoid uneven detection of the ZCPs. Phase commutation is corrected corresponding to the ZCPs detected using the new reference points to reduce current ripple, thereby leading to stable control of the sensorless BLDC motor. To this end, the control method adds or subtracts a preset certain value to/from a reference voltage to produce a new reference voltage, and detects ZCPs with respect to the new reference voltage to control drive of the sensorless concentrated winding BLDC motor.

Abstract: Disclosed is an apparatus, controlling the number of rotations per minute of a brushless DC motor, the apparatus comprising: a brushless DC motor that rotates at a constant speed when a rotation current is applied, and stops rotating when a stop current is applied; a pulse applying unit that outputs input pulses according to a pulse apply frequency, which is predetermined or inputted by a user; a rotation detecting unit that detects the number of rotation pulses, and outputs a predetermined output signal per rotation of the brushless DC motor; and a current controlling unit that applies the rotation current to the brushless DC motor in correspondence with the input pulse, and the stop current to the brushless DC motor in correspondence with the output signal.

Abstract: A technique for determining an alignment error of a Hall sensor location in a brushless DC motor drive, by measuring the back EMF waveform, preferably while the motor is coasting. According to the technique, an angular offset is calculated between a selected BEMF waveform and a selected Hall signal. Such offsets are preferably calculated for each phase individually. The offsets may be advantageously stored in the motor control unit and used to adjust the output motor control signals for maximum torque.

Abstract: A prior art direct back EMF detection method synchronously sampled motor back EMF during PWM “off” time without the need to sense or re-construct the motor neutral in a sensorless brushless DC (BLDC) motor drive system. Since this direct back EMF sensing scheme requires a minimum PWM “off” time to sample the back EMF signal, the duty cycle cannot reach 100%. Also in some applications, for example, high inductance motors, the long settling time of a parasitic resonant between the motor inductance and the parasitic capacitance of power devices can cause false zero crossing detection of back EMF. An improved direct back EMF detection scheme samples the motor back EMF synchronously during PWM “on” time at high speed. In the final system the motor back EMF can be detected during PWM “off” time at low speed, and it is detected during PWM “on” time at high speed.

Abstract: A vibration linear actuating device includes a vibrating linear actuator and a driver (52) for driving actuator. Actuator includes mover having permanent magnet magnetized in a radial direction, stator having coil (2) and facing the permanent magnet, and elastic body for coupling stator to mover. The driver includes driving section having switching element (Q5) for powering coil (2), output controller (27) for controlling switching element (Q5), zero-cross detector (25) for detecting a zero-cross point of back electromotive force generated in coil (2) and having an output to be fed back to the output controller (27). In this structure, the driver powers coil (2) in one way to keep mover vibrating in corporation with elastic body.

Abstract: A power source for a hybrid vehicle is provided which can protect its electric motor driving circuit from being damaged by a back electromotive force generated in a motor. The back electromotive force generated in an electric motor is detected by a high voltage detector circuit and converted by a step-down circuit into a low voltage which is then stored in a low-voltage second battery. Accordingly, as the back electromotive force does not become excessively high, it will be prevented from damaging a switching circuit. Also, the back electromotive force generated in the motor is charged in the low-voltage battery and can thus be supplied to a control circuit or any other component, contributing to the reduction of the fuel consumption of the hybrid vehicle. The back electromotive force can alternatively be diverted for charging a medium-voltage third battery.

Abstract: A low noise electronic three phase bridge controlled brushless DC motor suitable for whiteware appliance pumps and other appliance applications. Back EMF zero crossing sensing is used to determine rotor position and thus stator winding commutation times. Motor torque and speed are controlled by pulse width modulating the operation of that bridge switching device which has just been switched from an OFF state to an ON state on each new commutation. All three stator windings have current flowing in each winding commutation to improve motor current waveform and thereby reduce motor noise, but the current in one winding is always terminated before the end of the commutation period to allow the back EMF in that winding to be sensed to zero crossing.

Abstract: A method of correcting a pointing position of a pointer rotated by a stepper motor includes the steps of: performing a prereset operation in which the pointer is rotated to a reset operation starting position that represents a pointing position of the pointer which is shifted by a predetermined amount in a plus direction of a scale from a reset position where a pin which is rotated in conjunction with a rotation of the pointer abuts against a fixed stopper; after the prereset operation, performing a reset operation in which the pointer is rotated in a minus direction of the scale to the reset position; and after the reset operation, performing a correcting operation in which the pointer is rotated in the plus direction up to a reference pointing position which is indicated by previously stored reference pointing positional information.

Abstract: A system and a method for starting a brushless DC motor are provided. The method includes applying commutation pulses to at least two phase coils to induce a rotor to rotate to a starting position and then de-energizing the at least two phase coils. The method further includes applying commutation pulses to at least two phase coils to induce the rotor to rotate from the starting position in a predetermined direction. The method further includes de-energizing all phase coils for a first time interval after the rotor is rotating and sampling a back EMF signal in at least one of the phase coils to determine a first value indicative of an electrical period of the back EMF signal or a portion of an electrical period of the back EMF signal. Finally, the method includes applying commutation pulses to at least two phase coils for a second time interval, the second time interval being based on the first value.

Abstract: A drive circuit for operating a resonant motor includes a motor circuit, a feedback circuit, a control circuit, and a coil drive circuit. A feedback loop includes the motor circuit, the feedback circuit, and the control circuit. The feedback loop in conjunction with the coil drive circuit monitors, maintains, and adjusts the oscillatory motion of the resonant motor. The drive circuit is suitable for operating a resonant motor of an optical code reader.

Abstract: A system and a method for controlling a steering position of at least one rear wheel of a vehicle are provided. The vehicle has both a brushless electric motor with a plurality of electrical phase windings and a steering actuator. The brushless electric motor has a rotor configured to drive the steering actuator. The steering actuator is operably coupled to at least one rear vehicle wheel. The method includes determining a desired voltage value indicative of about one-half of a peak-to-peak voltage to be applied to each of the plurality of electrical phase windings of the brushless electric motor based on a desired rear vehicle wheel steering angle and a measured rear vehicle wheel steering angle. The method further includes determining when the desired voltage value is greater than a threshold voltage level. The method further includes calculating a phase advance angle based on at least the desired voltage value and the threshold voltage level.

Abstract: The invention relates to a control method and a control system for a motor. The control method and the control system of the invention transfer the motor dynamic equations of the synchronous d-q frame into a motor parameter (for example, the leakage inductance) and the equivalent counter electromotive force. Then the required control signals for the motor current control can be obtained. The control method of the invention not only preserves the merit of constant switching frequency of the convention PI-PWM control system, but also can eliminate the motor current phase-lag problem of the invention PI-PWM control system. Also, the control method of the invention will have the following characteristics and economic advantages such as high accuracy, fast response, low cost and robustness, etc.

Abstract: An apparatus, method and program product gradually and automatically accelerates or decelerates chair motor speed to achieve a smooth, nearly imperceptable movement of the chair. To this end, voltage is apportioned to the motor according to an acceleration profile.

Abstract: A starting circuit for an induction motor is provided whereby a stationary rotor flux is established then a stored charge supplied to a motor winding in order to provide a starting torque. Before applying a mains power supply to the motor after the starting torque has been applied, a back EMF is sensed, directly or indirectly, to provide an indication that the rotor is turning before the mains supply is connected to the motor. This provides a reliable and simple method for ensuring that a mains supply may be safely connected to the motor.