Techniques for monitoring the health of a three-phase induction motor are provided. An expected threshold value is calculated as a function of an expected ratio of current unbalance to voltage unbalance for the three-phase motor. Embodiments determine whether a measured current unbalance exceeds the expected threshold value. Responsive to the measured current unbalance exceeding the expected threshold value, a remedial action may be taken, such as generating diagnostic information or activating one or more protection operations for the three-phase induction motor.

Techniques for monitoring the health of a three-phase induction motor are provided. An expected threshold value is calculated as a function of an expected ratio of current unbalance to voltage unbalance for the three-phase motor. Embodiments determine whether a measured current unbalance exceeds the expected threshold value. Responsive to the measured current unbalance exceeding the expected threshold value, a remedial action may be taken, such as generating diagnostic information or activating one or more protection operations for the three-phase induction motor.

An induction machine with localized voltage unbalance compensation is disclosed. The use of an induction machine with a voltage unbalance correction compensator (VUC) may be used to maintain proper working conditions of the machine during intervals of voltage unbalance.

An induction machine with localized voltage unbalance compensation is disclosed. The use of an induction machine with a voltage unbalance correction compensator (VUC) may be used to maintain proper working conditions of the machine during intervals of voltage unbalance.

This method for controlling an asynchronous electrical motor (32) of a compressor system (10), comprises:—connecting (100) a capacitor bank (50) of the compressor system (10) in parallel with a first electrical motor (32) of the compressor system, this connection comprising connecting capacitors (52, 54, 56) of the capacitor bank (50) to windings of the stator of the first motor (32), by operating a switch unit (60) of the capacitor bank connected to an internal power bus (12);—starting (102) the first asynchronous electrical motor (32), by providing an input electrical current to the windings of the first motor (32) from the internal power bus (12);—disconnecting (108) the capacitor bank (50) from said first motor (32) once said motor (32) has started, this disconnection comprising disconnecting said capacitors (52, 54, 56) from the windings of the motor (32).

This method for controlling an asynchronous electrical motor (32) of a compressor system (10), comprises:—connecting (100) a capacitor bank (50) of the compressor system (10) in parallel with a first electrical motor (32) of the compressor system, this connection comprising connecting capacitors (52, 54, 56) of the capacitor bank (50) to windings of the stator of the first motor (32), by operating a switch unit (60) of the capacitor bank connected to an internal power bus (12);—starting (102) the first asynchronous electrical motor (32), by providing an input electrical current to the windings of the first motor (32) from the internal power bus (12);—disconnecting (108) the capacitor bank (50) from said first motor (32) once said motor (32) has started, this disconnection comprising disconnecting said capacitors (52, 54, 56) from the windings of the motor (32).

A control method includes setting, when a space phase difference of in-phase coils of the respective groups is represented by α, a time phase difference of electric currents to be supplied to the in-phase coils of the respective groups is represented by β, and a time phase difference of carrier frequencies with which the three-phase inverters are PWM-controlled, respectively, is represented by γ, values of β and γ so that any one or both of the following relationships are satisfied: γ=±(α+2β), and γ=±(α−β)/2, based on a result of comparison between a current amplitude of a primary component and a current amplitude of a secondary component of a carrier harmonic current, to control the dynamoelectric machine.

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 power tool includes a tool accessory, a motor, a control module, a power supply, and an operating switch. The operating switch includes a trigger mechanism, a current switch coupled to the trigger mechanism to be actuated by the trigger mechanism for connecting and disconnecting the electrical connection between the power supply module and the motor, and a signal switch coupled to the trigger mechanism to be actuated by the trigger mechanism at least configured to output a control signal to the control module to control the start of the motor.

An arrangement contains an asynchronous machine having a rotor and a stator. The arrangement is set up in a generator mode for feeding electrical energy into an AC voltage network. The arrangement is characterized in that the asynchronous machine can be doubly fed. The asynchronous machine can be connected in a matrix configuration to the AC voltage network by a modular multi-level converter, and the modular multi-level converter is set up in a motor mode of the arrangement for starting up the asynchronous machine while short-circuiting the rotor or the stator.