This disclosure relates to refrigerant compressors, and, in particular, relates to cooling for the power electronics of such compressors. An example refrigerant system includes a main refrigerant loop in communication with a condenser, an evaporator, and a compressor. The refrigerant system further includes at least one cooling line configured to direct refrigerant from the main refrigerant loop to cool a chamber containing electronic components. A method is also disclosed.

This disclosure relates to refrigerant compressors, and, in particular, relates to cooling for the power electronics of such compressors. An example refrigerant system includes a main refrigerant loop in communication with a condenser, an evaporator, and a compressor. The refrigerant system further includes at least one cooling line configured to direct refrigerant from the main refrigerant loop to cool a chamber containing electronic components. A method is also disclosed.

An object of the present invention is to provide a power conversion device including a plurality of inverter circuits connected in parallel to a load, the power conversion device being capable of performing control with a smaller number of microcomputers, having high reliability, and being advantageous for miniaturization and cost reduction. Provided are: a plurality of inverter circuits connected in parallel to a load; a microcomputer which controls the plurality of inverter circuits; a plurality of signal selection units which select a drive signal of each of the plurality of inverter circuits; and a first transmission path and a second transmission path which are connected in parallel between the microcomputer and the plurality of signal selection units and transmit the drive signal of each of the plurality of inverter circuits from the microcomputer to each of the plurality of signal selection units. Each of the plurality of signal selection units selects any one of a first drive signal transmitted from the first transmission path and a second drive signal transmitted from the second transmission path.

A power tool includes a motor and a power supply for supplying power to the motor. A driving circuit is connected to the motor. A voltage detection unit is used for detecting the voltage of the motor. A controller is configured to perform the following operations: if the motor voltage is greater than or equal to a preset voltage, the driving circuit will apply a voltage to the motor with a second slope, wherein the value range of the second slope is from 0 to 0.3. The disclosure also discloses a control method for starting under load of a power tool.

A power tool includes a motor and a power supply for supplying power to the motor. A driving circuit is connected to the motor. A voltage detection unit is used for detecting the voltage of the motor. A controller is configured to perform the following operations: if the motor voltage is greater than or equal to a preset voltage, the driving circuit will apply a voltage to the motor with a second slope, wherein the value range of the second slope is from 0 to 0.3. The disclosure also discloses a control method for starting under load of a power tool.

A variable frequency motor drive comprises a converter including a rectifier having an input for connection to an AC power source and converting the AC power to DC power. A DC bus is connected to the rectifier circuit. At least one bus capacitor is across the DC bus. An inverter receives DC power from the DC bus and converts the DC power to AC power to drive a motor. A controller is operatively connected to the converter. The controller comprises a speed control controlling the inverter responsive to a speed command to maintain a desired motor speed. A speed foldback control measures DC bus ripple voltage and regulates the speed command responsive to the measured DC bus ripple voltage.

In a dead time adjusting circuit, a switch voltage appearing at a connection node between a first output switch and a second output switch, which are connected in series between two different potentials, is monitored to detect a first dead time, which is from a time at which the second output switch is turned off to a time at which the first output switch is turned on, and a second dead time, which is from a time at which the first output switch is turned off to a time at which the second output switch is turned on, each of the first and second dead times being feedback-controlled to be identical to a predetermined target value.

A drive control method is applicable to a drive system including a driver, a bus and a motor, the motor being directly connected to the bus in a first connection mode or connected to the driver in a second connection mode. The drive control method includes the driver feeding an electric signal to the motor through the output port and simultaneously detecting its own actual output feature; and the driver determining whether the output port is connected to the bus according to the actual output feature. Upon the output port being determined not to be connected to the bus, the driver starts the motor normally. Upon the output port being determined to be connected to the bus, the driver disconnects the output port. In addition, a corresponding drive system, a processing system and a storage medium are disclosed.

A motor control device of the present invention supplies a detection current to a motor at predetermined time intervals, detects a voltage between the both ends of a smoothing capacitor when the detection current is supplied, and determines whether a connector is inserted or unplugged based on a change in the voltage between the both ends of the smoothing capacitor. Furthermore, if determining that the connector is unplugged, the motor control device decreases the voltage between the both ends of the smoothing capacitor to or below a defined value by discharging the smoothing capacitor.

The invention relates to a method of starting an electric motor (10) powered by an alternating power supply voltage, said method consisting of supplying current to the motor (10) with a delay t.sub.ret, during each period of the power supply voltage. The starting method comprises a first sequence in which the following steps are carried out during each n.sup.th period of the power supply voltage, where n is an integer number greater than 0: a) determine the value of a variation of a resistance of the electric motor during the previous n periods of the power supply voltage; b) compare said value of the variation of the determined motor resistance with a first threshold resistance value; c) if the value of the variation of the motor resistance is less than the first threshold value, reduce t.sub.ret. The invention also relates to a starter device and a computer program.