Abstract: A control system for a motor includes a pulse-width modulation module, a pulse skip determination module, and a duty cycle adjustment module. The pulse-width modulation module generates three duty cycle values based on three voltage requests, respectively. A plurality of solid-state switches control three phases of the motor in response to the three duty cycle values, respectively. The pulse skip determination module generates a pulse skip signal. The duty cycle adjustment module selectively prevents the plurality of solid-state switches from switching during intervals specified by the pulse skip signal.

Abstract: A digital filter is configured to convert, into a digital value, the duty ratio of a control signal subjected to pulse width modulation according to a target toque to be set for a fan motor to be driven. A sampling circuit is configured to perform sampling of the output value of the digital filter at a sampling timing that is asynchronous with respect to the cycle of the control signal, so as to generate a torque instruction value. A driving circuit is configured to drive the fan motor according to the torque instruction value thus generated.

Abstract: A driving circuit for a fan includes an initiation module for generating a switch signal according to a feedback signal, a control module coupled to the initiation module for generating a control signal according to the switch signal and a predetermined comparison signal, so as to drive the fan for a rotational operation, and a feedback module coupled to the fan for generating the feedback signal according to a conduction result of the fan, wherein the control module utilizes a pulse frequency modulation technique to generate the control signal, and the conduction result is realized via a voltage type or a current type to correspond to a rotational speed of the rotational operation.

Abstract: A motor controller according to the invention includes a driving IC and a magnetic sensor. The driving IC receives a driving signal for driving a motor and controls the rotation speed of the motor using the driving signal. The magnetic sensor detects the rotation speed of the motor. The driving IC includes a sensor signal output terminal and a driving signal input terminal. The sensor signal output terminal outputs a sensor signal generated by the driving IC based on a pulse signal from the magnetic sensor. The driving signal input terminal receives the driving signal. The sensor signal output terminal and the driving signal input terminal are connected by a connecting portion. The driving IC rotates the motor at a first rotation speed different from the rotation speed of the motor driven according to the driving signal using the sensor signal input to the driving signal input terminal.

Abstract: An exemplary inverter includes first, second and third legs connected in parallel to a line rail and a neutral rail. Each leg includes a first switch, a second switch, and a node between the first and second switches. The first leg further includes a voltage boosting section operable to selectively increase and decrease the voltage potential of the node of the first leg. The voltage boosting section may include a capacitor in parallel with the first and second switches. The first leg may further include a third switch in series with the voltage boosting section and between the voltage boosting section and the line rail, and a fourth switch in series with the voltage boosting section and between the voltage boosting section and the neutral rail.

Abstract: A power supply circuit includes two half bridge circuits, a controller and two terminals for connecting a motor. The controller includes a signal input terminal, a phase inverter, a wiring board having four soldering pads, and two conductors. The four soldering pads are connected to the signal terminal, an output terminal of the phase inverter, control terminals of lower switches of the two half bridge circuits. Two ends of the first conductor are connected to the first and the fourth soldering pads and two ends of the second conductor are connected to the second and the third soldering pads. Alternatively, two ends of the first conductor are connected to the first and the third soldering pads and two ends of the second conductor are connected to the second and the fourth soldering pads.

Abstract: A motor driving device according to the present invention includes: a PWM duty ratio detecting unit for detecting a target rotational speed based on a duty ratio of a PWM signal input from a host system; a PWM period detecting unit for detecting a period of the PWM signal; a PWM period error calculating unit for calculating an error between a PWM period output from the PWM period detecting unit and a PWM period previously set as a reference calculated by using the operational clock generator; a position detecting sensor for detecting a permanent magnet of the rotor; and an actual rotational speed calculating unit for calculating an actual rotational speed of the rotor by using a signal output from the position detecting sensor. The present motor driving device controls a speed while correcting the actual rotational speed based on the PWM period error.

Abstract: A system for soft starting a large AC motor may include a variable frequency drive (VFD) having a much lower voltage rating than the rated voltage of the AC motor. The VFD's voltage rating may be in a range of about 33% to about 67% of the AC motor's rated voltage. The AC motor may be coupled to a utility power source via conventional connections to leads of the AC motor's windings. The VFD may be connected to the AC motor via tapped connections within the windings of the AC motor such that the tap voltages are much less than the AC motor's rated voltage. A less expensive VFD may therefore be used to soft start the AC motor instead of a VFD having the same rated voltage as the AC motor. Methods of starting large AC motors with a VFD are also provided, as are other aspects.

Abstract: A runout measurement system is proposed for measuring the runout of a moving surface of a device having a rotating body, such as a mass storage device (100) (e.g. a hard disk drive) having a rotor which in use includes a rotating recording medium. A sensor (102) interacting with the moving surface obtains a displacement signal. The displacement signal is sampled by a sampling unit (104) controlled by a unit (109) which initiates sampling based on both a signal indicating a ZCP and the clock signal of a high frequency (e.g. 20 MHz) clock (106). Simultaneously, the same clock (106) is used by a counter 108 to measure the spacing between one or more ZCP times. This permits the correspondence between the sampling times and the angular position of the rotor to be found with a high accuracy which depends upon the clock frequency, and thereby allows calculation of repeatable runout (RRO) and non-repeatable runout (NRRO).

Abstract: A controller that performs pulse width modulation control of a three-phase inverter circuit includes a three-phase modulation voltage command value generation unit, a two-phase modulation voltage command value generation unit, a voltage command switching unit, and a PWM signal output unit. The voltage command switching unit switches a voltage command value to a two-phase modulation voltage command value when a determination value becomes larger than or equal to a first threshold value, and switches the voltage command value to a three-phase modulation voltage command value when the determination value becomes smaller than a second threshold value, which is smaller than the first threshold value.

Abstract: A power supply and control unit for submersed electric motors includes an enclosure which is jointly connected to the motor of a submersed electric pump and forms a hermetic chamber that contains an electronic power supply that can be connected to the motor. The unit includes a heat exchange means in the liquid state that completely fills the empty space within the hermetic chamber in order to transfer to the enclosure the heat generated by the electronic power supply.

Abstract: There are provided a signal duty detecting apparatus detecting a duty of a pulse width modulation (PWM) signal by counting a signal, among signals present in a preset period of the PWM signal, having a predetermined level or higher and a motor driving apparatus having the same. The signal duty detecting apparatus includes: a level detector detecting levels of an input signal; a counter counting the levels detected by the level detector; and a duty calculator calculating a duty of the input signal based on the levels counted by the counter.

Abstract: A bridge output circuit includes an output terminal, a high side transistor, a low side transistor, a high side driver for controlling a gate voltage of the high side transistor, a low side driver for controlling a gate voltage of the low side transistor, and a controller for controlling the high side and low side drivers. The low side driver includes a first current source, a second current source, and a first assist circuit. The controller is configured to control the turning-on and turning-off states of the first current source, the second current source and the first assist circuit.

Abstract: An object of the present invention is to efficiently heat a refrigerant retained in a compressor. An inverter control unit generates six drive signals corresponding to the respective switching elements of the inverter, and outputs the generated drive signals to the corresponding switching elements of the inverter to cause the inverter to generate a high-frequency AC voltage. Particularly, the inverter control unit generates a drive signal having a switching pattern A for turning on all the three switching elements on a positive voltage side or a negative voltage side of the inverter, and subsequent thereto, generates a drive signal having a switching pattern B for turning on two switching elements of the three switching elements and turning off one switching element thereof.

Abstract: A motor drive and a method in connection with a motor drive including a frequency converter are provided. The motor of the drive is connected to a load, and the motor is controlled with the frequency controller. The method includes the steps of converting changes in electrical quantities of the motor caused by actions affecting the load into observations representing the changes, selecting control symbols on the basis of matching of the sequences of observations with a set of valid patterns, and controlling the converter based on the selected symbols.

Abstract: A motor control device and a motor control method are disclosed herein, where the motor control device includes a signal conversion unit, a frequency multiplication unit, a profile generation circuit and a frequency converter unit. The signal conversion unit receives a rotation speed signal from a motor and converts the rotation speed signal into a digital signal. The frequency multiplication unit generates a frequency multiplication signal based on the digital signal. The profile generation circuit performs frequency division on the frequency multiplication signal to get a profile signal. The frequency converter unit generates a reference signal and compares the reference signal with the profile signal to output a motor control signal.

Abstract: A device includes a controller that receives current values generated by at least four parallel load commutated inverters (LCIs). The controller includes a source firing generator that generates independent source firing commands for each of the at least four parallel LCIs based on the received current values and transmits each of the independent source firing commands to a respective one of the at least four parallel LCIs, wherein the source firing commands are configured to set input phase angle values of the four parallel LCIs.

Abstract: The invention relates to a pitch drive circuit (50, 52, 54), which can operate in emergency mode, for a wind or water power plant (80), said circuit comprising at least one rectifier unit (14), at least one DC intermediate circuit (18), two inverter units (16-1, 16-2) and a pitch rotary current motor (38) with motor trains (30) which can be contacted on both sides. A first contact side (76-1) of the motor trains (30) is connected to a first inverter unit (16-1) and a second contact side (76-2) of the motor trains (30) is connected to a second inverter unit (16-2). At least one switching element (40) is connected to at least one contact side (76) of the motor trains (30).

Abstract: A control apparatus for a vibration type actuator using a vibration wave excited by a vibrating member, a movable member in contact with or indirectly connected to the vibrating member, including a command unit which gives a command indicating at least one parameter, an AC voltage generator which generates the AC voltage for applying the excitation force to the vibrating member, a variable adding unit which adds a predetermined variable to each of one or more parameters, a frequency response characteristic measuring unit which receives as an input a variable output and outputs a physical quantity and obtains a frequency response characteristic at one or more predetermined frequencies, a resonance frequency estimation unit which estimates a resonance frequency of the vibrating member, and a frequency range limiter which determines a frequency range for the AC voltage output by the AC voltage generator.

Abstract: The present disclosure discloses a converter system, which at least includes the first and second back-to-back converters. The first back-to-back converter includes a first rectifier module and a first inverter module. The first rectifier module is used to convert a first AC voltage to a first DC voltage. The first inverter module is used to convert the first DC voltage to a second AC voltage. The second back-to-back converter includes a second rectifier module and a second inverter module. The second rectifier module is used to convert the first AC voltage to a second DC voltage. The second inverter module is used to convert the second DC voltage to the second AC voltage. The converter system can suppress the circular current through the synchronous operation of the first and second rectifiers or the synchronous operation of the first and second inverters.

Abstract: A power train for a transport vehicle is provided. The power train includes an electric motor comprising a shaft, a stator and a rotor, a power supply system receiving direct input voltage and delivering a polyphase voltage to the motor. The system has a modulation factor equal to the voltage amplitude of each phase of the motor divided by the direct input voltage, and includes a sensor for the rotational speed of the rotor.

Abstract: A resonance suppression control block includes a high-pass filter for extracting an AC component of DC link voltage, and a gain section for outputting a correction signal obtained by multiplying the AC component by a gain. A control unit controls an inverter based on a signal obtained by adding the correction signal to the voltage instruction. Thus, a power conversion apparatus with a simple configuration can be obtained that can suppress resonance of a DC link section and omit extra work for performing adjustment again in accordance with a power supply frequency.

Abstract: A motor drive PWM rectifier includes a control section which generates the PWM signal in accordance with either a three-phase modulation scheme or a two-phase modulation scheme in which a PWM voltage command for one phase selected from among three phases each constituting the PWM voltage command in the three-phase modulation scheme is set and held at a level equivalent to a maximum value or minimum value of the PWM carrier and in which a PWM voltage command for the other two phases created by also applying an offset, required to achieve the setting, to the other two phases, a detecting section which detects three-phase AC current and outputs a detected current value, and a selecting section which selects the two-phase modulation scheme when the detected current value is larger than a first threshold value but smaller than a second threshold value, and otherwise selects the three-phase modulation scheme.

Abstract: An apparatus includes an inverter including a high-side switch coupled to a low-side switch, the inverter generating a time-varying drive current from a plurality of drive control signals, a positive rail voltage, and a negative rail voltage wherein controlling the switches to generate the time-varying drive current produces a potential transitory overshoot condition for one of the switches of the inverter; a drive control, coupled to the inverter, to generate the drive control signals and to set a level of each of the rail voltages responsive to a plurality of controller signals; and a controller monitoring one or more parameters indicative of the potential transitory voltage overshoot condition, the controller dynamically adjusting, responsive to the monitored parameters, the controller signals to reduce a risk of occurrence of the potential transitory voltage overshoot condition.

Abstract: There are provided an apparatus and method for controlling a fan motor. The apparatus for controlling a fan motor includes: a signal generating unit generating a pulse width modulation (PWM) input signal having a predetermined duty value; a memory storing duty correction values according to the duty value of the PWM input signal and driving characteristics of the fan motor therein; and a signal controlling unit generating a PWM output signal for operating the fan motor by using the PWM input signal and the duty correction values stored in the memory.

Abstract: Power conversion systems with active front end converters for example motor drives and power generation systems for distributed energy sources are presented with adaptive harmonic minimization for grid-tie converters for minimized or reduced total harmonic distortion in the line current spectrum including the source harmonic current and the grid-tie converter injected current spectrum referred to the line side.

Abstract: An apparatus for controlling an inverter is disclosed, the apparatus detecting a DC link voltage of the inverter and a load amount using an output current outputted from a motor to the inverter, and deducting a load amount detected at the time of occurrence of instantaneous power failure from a command frequency at the time of the occurrence of instantaneous power failure, whereby a command voltage and a command frequency driving the motor can be outputted.

Abstract: A protection circuit includes a first switch, a second switch and a third switch. The first switch, the second switch and the third switch are configured to generate lock signals indicative of an electrical voltage transition on the respective phases of a multi-phase power signal. A control circuit is configured to prevent the first switch from changing state if the second switch or third switch is changing state.

Abstract: A motor control circuit for a motor is provided. The motor control circuit drives the motor based on torque command data. The torque command data is output by adding speed error data output from a speed error detecting section based on a first reference clock and a speed pulse and phase error data output from a phase error detecting section based on a second reference clock and the speed pulse. Each of the speed error data and the phase error data is output within a detection range set by a setting section provided for each of the speed error detecting section and the phase error detecting section.

Abstract: The characteristic is defined by a characteristic line that connects a lowest point at which the duty of the PWM signal is a minimum value and the rotation command signal is a minimum rotation command signal, and a highest point at which the duty of the PWM signal is a maximum value and the rotation command signal is a maximum rotation command signal. The duty calculating circuit updates the characteristic so that the characteristic line passes through a first control point at which the duty of the PWM signal is a value set based on the first setting signal and the rotation command signal is a first rotation command signal between the minimum rotation command signal and the maximum rotation command signal.

Abstract: A motor load control apparatus capable of suppressing heat generation of an electronic switch and suppressing occurrence of noise associated with rotation of a fan and vibration of the fan is provided. A switch section (17) in which a first electronic switch (T1) and a second electronic switch (T2) are connected in parallel is provided, and the first electronic switch (T1) is driven by a PWM signal with a predetermined duty ratio and a predetermined frequency and the second electronic switch (T2) is driven in a state of delaying the PWM signal by which the first electronic switch (T1) is driven by a predetermined time. Consequently, as compared with the case of one electronic switch, a heating value of each of the electronic switches can be reduced and radiation measures of the whole apparatus can be reduced. Further, noise or vibration occurring by PWM control can be reduced by changing delay time at random.

Abstract: An electrical controller for electric motors is provided. A control system for an electric motor comprises a supply for supplying excitation current to different windings of the motor at any given time. Furthermore, the amplitude of the excitation current is independently variable of the timing and duration of the application of the excitation current to the windings. This allows increased control of the motor and facilitates the operation of the motor at high mechanical and/or electrical speeds.

Abstract: A power tool includes a tool housing, an electric motor inside the housing, and a power interface facilitating a connection to a power source. At least four actively-controlled power components are configured as an H-bridge to modulate a supply of power from the power interface to the electric motor. A user-actuated input unit outputs a first signal indicative of a desired power output level to the electric motor and a second signal indicative of a desired direction of current flow to the electric motor. A control unit controls the supply of power to the electric motor using two of said power components with synchronous rectification for pulse-width modulation (PWM) of the supply of power based on the first signal, and to control the direction of current flow to the electric motor using the other two of said power components based on the second signal.

Abstract: Control device (30) and method for controlling an AC motor (18) by means of a motor control unit (19). The control device (30) includes an AFE unit (33) arranged in parallel with the rectifier unit (12), which AFE unit (33) is arranged for, under normal operation, to work as an active filter and inject super-harmonic current components opposite of the ones generated by the rectifier unit (12) to counteract the current distortion, seen from the grid side. When the motor control unit (19) is running regenerative, the AFE unit (33) will work as a 4-quadrant converter and supply energy back to the supply grid (13). Advantages of the invention are reduced physical size, lower cost and improved efficiency compared to existing solutions of motor drive with frequency converters in weak grids, where the motor drive must handle regenerative operation.

Abstract: There is provided a motor driving apparatus. The motor driving apparatus includes: a duty adjusting unit adjusting a duty of a PWM signal in response to a detection signal from a hall sensor, adjusting a duty value in a partial period of the entire duty period to be higher than a target duty value that is to be controlled and a duty value in another partial period thereof to be lower than the target duty value that is to be controlled, and adjusting an average duty value in the entire duty period to follow the target duty value; a signal generating unit receiving a PWM control signal and generating the PWM signal of which the duty is adjusted according to the adjustment of the duty; and a driving controlling unit controlling driving of a motor in response to the detection signal of the hall sensor and the PWM signal.

Abstract: Provided is a regenerative medium voltage inverter, the inverter being such that regenerative operation is enabled by changing structure of input terminal of a unit power cell at a series H-bridge medium voltage inverter, and a dynamic braking resistor is not required to reduce the size of a DC-link capacitor over that of a conventional medium voltage inverter.

Abstract: A control device of an alternating current motor includes a voltage phase setting portion, an offset detecting portion, a switching controlling portion obtaining a timing at which a voltage waveform is switched between a pulse width modulation waveform and a square waveform per half cycle of an electric angle, and a waveform switching portion switching the voltage waveform to the pulse width modulation waveform on a positive side and the square waveform on a negative side in a case where the offset value is a positive value, switching the voltage waveform to the pulse width modulation waveform on the negative side and the square waveform on the positive side in a case where the offset value is a negative value, and switching the voltage waveform to the square waveform on the positive side and the square waveform on the negative side in a case where the offset value is zero.

Abstract: In order to lower electromagnetic noise, normally, a carrier frequency of a inverter or controlling drive of a motor mounted on an electrically powered vehicle is changed periodically or randomly within a first frequency range set in advance, as the time elapses. While a vehicle speed is low, the carrier frequency is changed periodically or randomly within a second frequency range set in advance to be wider than the first frequency range and to be equal in central frequency to the first frequency range, as the time elapses. The second frequency range is set to include a resonant frequency of a specific mechanical oscillation system higher in electromagnetic noise generated at a natural resonant frequency, among a plurality of mechanical oscillation systems formed by equipment mounted on the electrically powered vehicle. On the other hand, the first frequency range is set not to include the resonant frequency.

Abstract: A chiller system (200) includes a motor (212), a motor controller (214) connected to the motor (212), the motor controller (214) operative to send a control signal to the motor (212), a rectifier (206) connected to an alternating current (AC) power source (204), the rectifier (206) operative to receive AC power and output direct current (DC) power, a DC bus (208) connected to the rectifier (206), a first inverter (210) connected to the DC bus (208) and the motor (212), the first inverter (210) operative to receive DC power from the DC bus (208) and output AC power to the motor (212), and a second inverter (213) connected to the DC bus (208) operative to receive DC power and output AC power to the motor controller (214).

Abstract: In a synchronous machine starting device, an AC voltage detection unit detects AC voltage supplied to an armature of a synchronous machine through an electric power line from a power conversion unit. The AC voltage detection unit has a first output end and a second output end isolated from the electric power line, transforms AC voltage supplied through the electric power line at a first ratio to output the transformed voltage from the first output end, and transforms AC voltage supplied through the electric power line at a second ratio and then limits the transformed voltage to a prescribed positive voltage value or lower and a prescribed negative voltage value or higher for output from the second output end. Then, a detected voltage selection unit selects one of the voltage received from the first output end and the voltage received from the second output end, and outputs the selected one to a rotor position detection unit.

Abstract: Methods, system and apparatus are provided for reducing power loss in an electric motor drive system that includes an electric machine and an inverter module. A controller determines whether a torque command (Tcmd) is less than a minimum torque threshold (Tmin) that is required to disable the inverter module, and if so, increments a counter and determines whether the torque command (Tcmd) remains less than the minimum torque threshold (Tmin). When the torque command (Tcmd) remains less than the minimum torque threshold (Tmin), the controller checks to determine whether a current count value (n) maintained at the counter is greater than a count threshold (nth), and if so, the controller can generate a disable signal to disable switching within the inverter module.

Abstract: A control apparatus for a switching circuit includes a controller, a target-rotational-speed acquiring device, a target-torque acquiring device, and an ON-time varying device. The controller is configured to turn on a bidirectional conduction switching device provided parallel to a reverse conducting device through which a commutation current flows. The target-rotational-speed acquiring device is configured to acquire a target rotational speed of an alternating current motor. The target-torque acquiring device is configured to acquire a target torque of the alternating current motor. The ON-time varying device is configured to vary, on a basis of the target rotational speed and the target torque, an ON time period during which the bidirectional conduction switching device provided parallel to the reverse conducting device through which a commutation current flows is turned on.

Abstract: An apparatus operable in a wet environment includes a voltage doubler circuit including a pair of diodes, a pair of direct current switching elements connected between the respective diodes and a common point, a controller, an interface connected to the controller for receiving external status signals, and a switching arrangement responsive to signals from the controller to select the full power mode or a controlled power mode. In the controlled power mode, the switching elements are switched in a predetermined sequence such that only one of the switching elements conducts current during any one half cycle of the AC output voltage applied to the motor.

Abstract: In an electric tool, in order to carry out a phase control or an antiphase control using a transistor with the cost lower and structure simpler, and to suppress an electromagnetic noise, constant voltage generating means of the electric tool includes a series circuit of a resistor 91 and a diode 93 and a parallel circuit of a capacitor 95 and a Zener diode 97, one end of the resistor 91 is connected to a node between an AC power supply 1 and an AC motor 3, a cathode of the diode 93 is connected to one end of the capacitor 95 and a cathode of the Zener diode 97, and the other end of the capacitor 95 and an anode of the Zener diode 97 are connected to sources of transistors 51, 52. One ends of resistors 53, 54 are connected to gates of the transistor 51, 52, and a voltage at the other ends of the resistor 53, 54 are switched between a voltage at a node between the series circuit and the parallel circuit and a voltage of the source of the transistors 51, 52 so that the transistors 51, 52 are turned ON or OFF.

Abstract: A power tool includes a tool housing, an electric motor inside the housing, and a power interface facilitating a connection to a power source. At least four actively-controlled power components are configured as an H-bridge to modulate a supply of power from the power interface to the electric motor. A user-actuated input unit outputs a first signal indicative of a desired power output level to the electric motor and a second signal indicative of a desired direction of current flow to the electric motor. A control unit controls the supply of power to the electric motor using two of said power components with synchronous rectification for pulse-width modulation (PWM) of the supply of power based on the first signal, and to control the direction of current flow to the electric motor using the other two of said power components based on the second signal.

Abstract: A control device that controls a plurality of inverters respectively provided corresponding to a plurality of alternating-current electric motors so as to control the plurality of alternating-current electric motors by current feedback. The control device comprises a carrier frequency setting unit that individually selects and sets one of a plurality of carrier frequencies, each of which is a frequency of a carrier for generating switching control signals for the inverter based on a pulse width modulation method, for each of the plurality of inverters, and a switching timing table that specifies a switching timing serving as a permissible timing of switching to a different carrier frequency pair from each of a plurality of carrier frequency pairs each of which is composed of a combination of the carrier frequencies set for each of the plurality of inverters.

Abstract: A rotating electrical-machine control system is provided with: a rotating electrical-machine comprising a rotor further comprising permanent magnets that are divided into a dividing-number of sections; an inverter circuit that drives the rotating electrical-machine by PWM control, using a carrier wave having a carrier frequency; a storage unit that has stored therein a relationship file that indicates the relationship between the dividing-number of the magnets, the magnet temperature, and the carrier frequency; and a control apparatus.

Abstract: The present invention relates to an inverter device including an upper arm switching circuit, a lower arm switching circuit, a control unit that controls the upper arm switching circuit and the lower arm switching circuit, a plurality of voltage-driven switching elements forming the upper arm switching circuit, a plurality of current-driven switching elements forming the lower arm switching circuit, and a bootstrap circuit that applies a driving voltage to the switching elements of the upper arm switching circuit and the lower arm switching circuit. With this configuration, the circuit loss is reduced and thus efficiency is improved.

Abstract: Method and arrangement for connecting an AC electric motor (M1, M2, . . . MN) to an AC electricity network (L) in a system which comprises a frequency converter (FC), with which the motor is started, and contactors (S11, S12, S21, S22, SN1, SN2), in which method the supply source is changed by means of the contactors from the frequency converter to a direct network supply, in which method the frequency converter is stopped before changing the supply source, and in which method in connection with changing the supply source the control of the contactors is started before stopping the frequency converter.

Abstract: An apparatus includes an inverter including a high-side switch coupled to a low-side switch, the inverter generating a time-varying drive current from a plurality of drive control signals, a positive rail voltage, and a negative rail voltage wherein controlling the switches to generate the time-varying drive current produces a potential transitory overshoot condition for one of the switches of the inverter; a drive control, coupled to the inverter, to generate the drive control signals and to set a level of each of the rail voltages responsive to a plurality of controller signals; and a controller monitoring one or more parameters indicative of the potential transitory voltage overshoot condition, the controller dynamically adjusting, responsive to the monitored parameters, the controller signals to reduce a risk of occurrence of the potential transitory voltage overshoot condition.