A control method for a centrifugal compressor and an air conditioning system. The control method for the centrifugal compressor includes: S100, when an inlet opening of the centrifugal compressor is below a first preset value, shutting down a drive motor of the centrifugal compressor; or S200, when the inlet opening of the centrifugal compressor is not below the first preset value, performing the following operations in a preset order: decreasing the inlet opening of the centrifugal compressor, and increasing a rotate speed of the centrifugal compressor.

A speed control method of direct current motor fans is revealed. The method used for starting and speed adjustment of the DC motor fan according to a temperature signal includes the following steps. First using a first voltage to start a DC motor fan during a start period and the first voltage is larger than the lowest voltage required for keeping the DC motor fan rotating. Then provide the DC motor fan with the lowest voltage which keeps the DC motor fan rotating during a low-load period after the start period. When a temperature represented by the temperature signal reaches a preset heat dissipation temperature range, a working voltage is adjusted proportionally and linearly according to the temperature signal for speed adjustment of the DC motor fan. The present method has advantages of high starting torque, noise cancellation, energy-saving, and low cost.

A fan, in particular axial fan and preferably backward-curved radial fan, having an impeller equipped with blades, an electric motor for rotating the impeller and a device for determining the airflow when the impeller is rotating. The device for determining the airflow includes a volume flow measuring wheel arranged in the air flow, which is arranged upstream of the impeller on the inflow side. The air volume flow is calculated or derived from the rotational speed of the volume flow measuring wheel.

Methods, devices, and systems for adjusting for air flow temperature changes in an aspirating smoke detector are described herein. In some examples, one or more embodiments include a blower configured to cause air to flow through the aspirating smoke detector, and a controller configured to determine a temperature of the air flowing through the aspirating smoke detector has changed by a particular amount and adjust a speed of the blower in response to compensate the air flowing through the aspirating smoke detector that has changed by the particular amount.

A system and a method for automatically correcting a rotational speed of a motor of a fan are provided. After the fan is moved from an open space to a closed space, a sample and hold circuit samples and holds working periods of a driving signal by which the motor is driven to rotate at a first rotational speed as a first sampled working period, and a working period of a driving signal by which the motor is driven to rotate at a second rotational speed. An arithmetic circuit calculates a difference between the first sampled working period and a first reference working period, and a difference between the second sampled working period and a second reference working period. The arithmetic circuit calculates other working periods of driving signals by which the motor is driven to rotate at other rotational speeds based on the differences.

Embodiments of the present disclosure relate to a refrigeration system that includes a compressor configured to circulate refrigerant along a refrigerant loop, a motor configured to drive the compressor, and a variable speed drive coupled to the motor and configured to supply power to the motor. The variable speed drive includes a primary winding of a step down transformer coupled to an alternating current (AC) power source, a first secondary winding of the step down transformer, where the first secondary winding is configured to supply power at a variable supplied voltage to the motor when the motor operates below a threshold voltage, and a second secondary winding of the step down transformer, where the second secondary winding is configured to supply power at a fixed supplied voltage when the motor operates at or above the threshold voltage.

Disclosed is a fan. The fan includes a support; a first motor installed on the support, the first motor having a first rotation shaft; a first blade installed on the first rotation shaft; a second motor installed on the support, the second motor having a second rotation shaft and being coaxial with the first motor; a second blade installed on the second rotation shaft, a tilt direction of the second blade being opposite to a tilt direction of the first blade; and an electric control board electrically connected to the first motor and the second motor and configured to control a relative rotation of the first motor and the second motor.

A motor drive control device controls driving of a motor by performing PWM control of turning on-off of an arm switching element of a PWM inverter outputting a three-phase AC voltage to the motor, and detects current values of respective phases of the three-phase AC voltage. The motor drive control device turns off a lower arm switching element for a largest phase by causing a first PWM pulse based on a largest phase voltage command and a carrier signal throughout an entire first period during which the carrier signal rises or falls to be at a low level. The motor drive control device turns on a lower arm switching element for a smallest phase by causing a second PWM pulse based on a smallest phase voltage command and the carrier signal throughout an entire second period during which the carrier signal rises or falls to be at a high level.

A motor drive control device 1 includes a drive voltage generation circuit 13 configured to generate a drive voltage Vin based on a first supply voltage Vdc inputted to a first terminal P1 and generate the drive voltage Vin based on a second supply voltage inputted to a second terminal P2 when a supply of the first supply voltage Vdc is stopped, a control circuit 21 configured to be operable by the drive voltage Vin, generate a drive control signal Sd based on a drive command signal Sc, generate a motor driving information signal So and output the motor driving information signal So from a third terminal P3 and a motor drive circuit 10 configured to output a drive signal to the motor 3, in which the control circuit 21 monitors the first supply voltage Vdc and outputs history information 300 relating to operation of the motor 3 from the third terminal P3 as the motor driving information signal So upon detecting that the supply of the first supply voltage Vdc is stopped.

A system for controlling operation of a ceiling fan is provided. The ceiling fan includes a fan device and a light device, and can be operated via a user operation module that is to be operated by direct operation, or a wireless receiver module that receives a wireless control signal. Within a predetermined control duration from the time of activation, the ceiling fan can, upon receipt of an operation signal from the user operation module or a wireless control signal from the wireless receiver module, switch to operate in a mode where the ceiling fan is controlled via one of the user operation module and the wireless receiver module that corresponds to the signal received thereby.