The disclosure relates to a method for determining an incorrect operating state of an electrical machine with the aid of an electronic circuit having at least one comparator. The electrical machine is controlled with a pulse width modulation signal. The pulse width modulation signal is demodulated. A first signal, which represents the demodulated pulse width modulation signal, is compared with a second signal. The second signal represents a rotational speed or a rotational angle of the electrical machine and/or a current intensity of the electrical machine. This comparison is carried out with the aid of the at least one comparator. An error signal is generated based on the comparison in order to determine the incorrect operating state of the electrical machine.

The invention relates to an electric machine tool comprising an electric motor, a motor control unit for operating the electric motor, an input interface for entering a target specification of an operating mode of the electric motor into the motor control unit, and a motor sensor device for detecting the operating mode of the electric motor. A slave control unit is provided, which is independent from the motor control unit and communicatingly connected to the motor sensor device and the input interface and designed to compare the operating mode of the electric motor detected by the motor sensor device with the target specification entered via the input interface, and to influence the operating mode of the electric motor in case of a defined deviation of the operating mode from the target specification by means of a control device.

A drive apparatus includes a DC link; a rectifier to convert power of an external power supply into predetermined DC power to be supplied to the DC link; a motor to rotationally drive a compression mechanism; a supporter to magnetically support a rotating shaft of the compression mechanism; a first driver to drive the motor with power from the DC link, to cause the motor to execute regenerative operations of converting power from the rotating shaft into electric energy, and to output regenerative power to the DC link; and a second driver to drive the supporter with the power from the DC link, wherein the first driver causes the motor to execute the regenerative operations so that a voltage of the DC link becomes higher than a voltage of the DC link when the power of the external power supply is normally supplied.

The present disclosure provides a motor driving device capable of inhibiting unstable driving of a motor even in the occurrence of a sudden fluctuation of a power supply voltage. The motor driving device includes a power supply voltage sudden fluctuation detector, a power supply voltage fluctuation width generator and a current limit value setting unit. The power supply voltage sudden fluctuation detector detects a sudden fluctuation in a direction in which the power supply voltage rises. The power supply voltage fluctuation width generator detects a fluctuation width of the power supply voltage. When the sudden fluctuation is detected by the power supply voltage sudden fluctuation detection unit, a current limit value of the current limit value setting unit is reduced from a normal value and corrected by the correction width corresponding to the fluctuation width of the detected power supply voltage.

An apparatus for controlling a rotary electric machine includes: first and second inverters corresponding to first and second winding groups; first and second voltage detectors; and first and second control units. Each of the first and second inverters includes plurality of switching elements. The first and second voltage detectors each detects input voltage of corresponding inverter. The first control unit limits a first current command value of the first winding group, when both of the first and second inverter input voltages are in normal, and a first differential value is larger than a determination threshold, and the second control unit limits a second current command value of the second winding group, when both of the first and second inverter input voltages are normal, and a second differential value is larger than the determination threshold.

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).

Power conversion systems and methods are provided for ride through of abnormal grid conditions or disturbances, in which a system rectifier is operated in a first mode to regulate a DC voltage of an intermediate DC circuit, an inverter is operated in the first mode to convert DC power from the intermediate DC circuit to provide AC output power to drive a load. In response to detecting an abnormal grid condition, the system changes to a second mode in which the rectifier is turned off and the inverter regulates the DC voltage of the intermediate DC circuit using power from the load.

A free piston Stirling refrigerator of the present invention has a cylinder provided inside a casing; a piston and a displacer that are provided in a way such that they are capable of reciprocating inside the cylinder; a linear motor for reciprocating the piston; and a control unit for controlling the operation of the linear motor. Particularly, the control unit has an inverter circuit for generating an alternating current with a given frequency and then supplying the alternating current to the linear motor; a current detection circuit for detecting the current outputted from the inverter circuit; and a control circuit for controlling the output from the inverter circuit based on a turbulence in the current detected by the current detection circuit. Thus, collisions between the piston and the displacer (i.e. hitting) can be restricted through an inexpensive configuration and a simple control.

A functional safety system with high reliability is provided. The functional safety system includes power source apparatuses VS1 and VS2, voltage monitoring apparatuses VM1 and VM2, semiconductor devices SC1 and SC2, interruption circuits IN1 and IN2, and a motor MT. A the voltage converting circuit DA1 of the voltage monitoring apparatus VM1 generates a detected voltage VA1 from a power source voltage VDD1 on the basis of a switching signal VC1, and a voltage converting circuit DA2 of the voltage monitoring apparatus VM1 generates a detected voltage VA2 from the power source voltage VDD1 on the basis of a switching signal VC1.

A current controller for an electric machine that includes an input, an output, a threshold generator and a comparator. The threshold generator stores a scaling factor and includes a PWM module that operates on a reference voltage to generate a threshold voltage. The duty cycle of the PWM module is then defined by the scaling factor. The comparator compares a voltage at the input against the threshold voltage and causes an overcurrent signal to be generated at the output when the voltage at the input exceeds the threshold voltage.