A capacitor and other components are added to the motor starter control circuit in order to supply power to the contactor coil during undervoltage events. In order to avoid adding an additional active device in the control circuit to control the application of capacitor voltage to the contactor coil, a microprocessor-based motor protective relay may be used to switch the capacitor in or out in a controlled manner. The motor protective relay is used for overload protection as well as for undervoltage switching of the capacitor. The motor protective relay is microprocessor-based and offers user-configurable general-purpose logic and math processing functions to control the capacitor switching.

A capacitor and other components are added to the motor starter control circuit in order to supply power to the contactor coil during undervoltage events. In order to avoid adding an additional active device in the control circuit to control the application of capacitor voltage to the contactor coil, a microprocessor-based motor protective relay may be used to switch the capacitor in or out in a controlled manner. The motor protective relay is used for overload protection as well as for undervoltage switching of the capacitor. The motor protective relay is microprocessor-based and offers user-configurable general-purpose logic and math processing functions to control the capacitor switching.

To provide a heat pump device capable of avoiding resonance of a power supply by reducing an increase in the number of components, installation space, and cost. A heat pump device is equipped with: a compressor 3 for compressing a refrigerant; a converter 11 for converting a voltage of an alternating current power supply 2 into a boosted direct current; an inverter 13 for converting the direct current output of the converter 11 into an alternating current, supplying the alternating current to the compressor 3; a voltage detector 36 for detecting an input voltage to the converter 11; a stop controller 43 for stopping operation of the converter 11 and the inverter 13 when resonance occurs in the voltage detected by the voltage detector 36; a limit controller 45 for sending an instruction to limit an input current to the converter 11 so as to avoid the resonance; and a manually operable input interface 46 for sending an instruction to cause the limit control unit 45 to operate.

A method of controlling a motor of an electric power assisted steering system, the motor having a plurality of phases, the method comprising taking as an input an input signal indicative of a desired assistance torque and determining from the desired assistance torque a voltage to be applied to each of the phases of the motor, in which the step of determining the voltage to be applied to each of the phases comprises limiting the voltage determined to be applied to each of the phases of the motor dependent upon the voltage provided by a power supply to the motor.

A secure roller controller of a roller conveyor system for logistics services includes a monitoring circuit, a controller module and a driving circuit and is electrically connected to a motor. The monitoring circuit is electrically connected to the controller module and the driving circuit to receive a power signal from the driving circuit. The controller module is electrically connected to the driving circuit to receive the power signal and instruct the driving circuit to drive the motor for speed adjustment according to the power signal. When instantly detecting that the power signal is irregular, the monitoring circuit transmits an irregularity signal to the controller module for the controller module to instantly decelerate a rotation speed of the motor to a safe rotation speed through the driving circuit. Accordingly, burn-down of the motor and the secure roller controller can be avoided to enhance operational stability and safety.

A method and a device for bringing a textile machine to a controlled standstill in the event of a failure of the power supply, and a correspondingly equipped textile machine, the textile machine having at least two axes that are driven in synchronization by respective electric motors (M1-M.sub.5) connected to a common intermediate voltage circuit (1), and in which at least one electric motor acting as power generator can supply electric power to at least one other electric motor via the common DC bus (1), and in which the voltage (V) on the common DC bus is controlled by varying at least two variables in such a way that the voltage follows a previously defined curve while the textile machine is being brought to a standstill.

An intelligent power module and a controller for an air conditioner are provided. For the intelligent power module, an adjust circuit is additionally provided between a respective drive circuit and a respective IGBT transistor. The adjust circuit detects a change in the voltage of a low voltage power supply of the intelligent power module in real time, and disables the output of the module when the voltage is detected to be too low due to fluctuation of the low voltage power supply. This operation releases the charge accumulated in the IGBT transistor, when energy storage of a drive motor causes charge accumulation of the IGBT transistor. The adjust circuit can continue releasing the charge when the low voltage power supply is restored to normal, to prevent the operating reliability of the module from being affected by the impact of the charge on internal circuits of the module.

An inverter device that includes an inverter circuit that converts power between DC power and multi-phase AC power; a drive circuit that transfers a drive signal to each of a plurality of switching elements that form the inverter circuit to cause a switching element of the plurality of switching elements to perform turn-on, in which the switching element is caused to transition from an off state to an on state, and turn-off, in which the switching element is caused to transition from the on state to the off state; and a current detection circuit that detects a current that flows through each of the plurality of switching elements.

A motor drive device includes an inverter circuit, a switching circuit that switches between conduction and interruption between a power supply and the inverter circuit, and a switching driver that outputs, to the switching circuit, a command voltage which commands a switching operation. The switching circuit includes a first field-effect transistor (FET) and a second FET connected in series with sources of each other in order from a side of the power supply, and the switching driver includes an output circuit that outputs an interruption command voltage in a case in which a potential difference between drains of the FETs exceeds a threshold value, and a delay circuit that causes a timing at which the command voltage is input to a gate of the first FET to be later than a timing at which the command voltage is input to a gate of the second FET.

A monitoring system for an electric power-assisted steering system comprising a DC power supply; an inverter bridge including a plurality of bridge switches selectively connecting phases of a multi-phase electric motor to the DC power supply, the multi-phase electric motor being configured to provide power-assistance to a steering system of a vehicle; a bridge driver circuit for providing control signals to the inverter bridge; and a DC link capacitor circuit interposed between the DC power supply and the inverter bridge, the DC link capacitor circuit at least one DC link capacitor. The monitoring system comprises a monitoring circuit configured to monitor the integrity of the DC link capacitor circuit, and outputting a ripple value indicative of a ripple voltage in an output of the DC power supply; and comparison means for comparing the ripple value with at least one ripple parameter indicative of a fault in the DC link capacitor circuit and determining whether a fault is present.