Abstract: Provided are a method and system for controlling an electric motor, and a controller. The method comprises: controlling an electric motor to operate in an open-loop manner; determining whether a rotational speed of the electric motor reaches a preset rotational speed; if so, determining whether the absolute value of an angle difference between an open-loop angle and a calculated position angle of the electric motor is greater than a preset angle; and if the absolute value of the angle difference is less than or equal to the preset angle, controlling the electric motor to operate in a closed-loop manner so as to avoid the situation where the electric motor cannot operate stably due to problems such as electric motor speed vibration caused by too large an angle difference between the open-loop angle and the position angle.

Abstract: Provided is a controller, an air conditioner, and a high-pressure protection circuit. The controller includes a first rectifier unit, a power conversion unit, a high pressure switch (HPS) wiring terminal, a low-voltage control unit, and a high-voltage operating unit. An input end of the first rectifier unit is capable of being electrically connected to an input power supply. An output end of the first rectifier unit is electrically connected to an input end of the power conversion unit. An output end of the power conversion unit is electrically connected to a power supply end of the low-voltage control unit. The HPS wiring terminal is connected to the front end of the power supply end of the low-voltage control. The controller has a function of high-pressure protection.

Abstract: An overcurrent protection circuit and a controller are provided. The overcurrent protection circuit includes a sampling circuit, a comparator circuit, a D flip-flop, and an output signal control circuit. The sampling circuit samples a current of a controlled circuit to obtain a sample signal. The comparator circuit compares the sample signal with a reference signal, and generates an overcurrent signal if the sample signal is greater than the reference signal. The D flip-flop generates a first level signal in response to the overcurrent signal. The output signal control circuit outputs, in response to the first level signal, a control signal for reducing the current of the controlled circuit. The controller includes a controlled circuit and the overcurrent protection circuit.

Abstract: Provided are a motor control method, a motor control device and a variable frequency drive. The method includes: performing an amplitude limiting on a command torque to obtain a target torque; calculating a target current based on the target torque; determining whether an amplitude of the target current is greater than a current limiting amplitude; performing an amplitude limiting on current components of the target current, when the amplitude of the target current is greater than the current limiting amplitude; and controlling a motor based on the current components of the target current after being performed the amplitude limiting. Thus, an amplitude limiting on current of a motor is achieved by performing amplitude limiting on torque and current.

Abstract: An overcurrent protection circuit and a controller are provided. The overcurrent protection circuit includes a sampling circuit, a comparator circuit, a D flip-flop, and an output signal control circuit. The sampling circuit samples a current of a controlled circuit to obtain a sample signal. The comparator circuit compares the sample signal with a reference signal, and generates an overcurrent signal if the sample signal is greater than the reference signal. The D flip-flop generates a first level signal in response to the overcurrent signal. The output signal control circuit outputs, in response to the first level signal, a control signal for reducing the current of the controlled circuit. The controller includes a controlled circuit and the overcurrent protection circuit.

Abstract: Provided are a motor control method, a motor control device and a variable frequency drive. The method includes: performing an amplitude limiting on a command torque to obtain a target torque; calculating a target current based on the target torque; determining whether an amplitude of the target current is greater than a current limiting amplitude; performing an amplitude limiting on current components of the target current, when the amplitude of the target current is greater than the current limiting amplitude; and controlling a motor based on the current components of the target current after being performed the amplitude limiting. Thus, an amplitude limiting on current of a motor is achieved by performing amplitude limiting on torque and current.

Abstract: An air conditioner controller and a safety protection circuit for the same are provided. The air conditioner controller includes a central processing unit, a drive unit, a safety locking unit and a protection detection unit, where the central processing unit is configured to output an air conditioner control signal; the air conditioner motor drive unit is configured to receive a drive control signal output from the safety locking unit and the detection protection signal, and output a drive signal to control an operation of an air conditioner motor; the safety locking unit is configured to receive the detection protection signal and the air conditioner control signal, output the drive control signal, and control the air conditioner control signal to be transmitted or cut off based on the detection protection signal output from the protection detection unit.