An embodiment of method used to control operation of a screw compressor of a refrigeration system may include receiving status signals regarding operation of the screw compressor of the refrigeration system. The method may further include determining an operating point of the screw compressor based upon the received status signals, and selecting a torque profile for the screw compressor based upon the operating point. The method may also include driving the screw compressor per the selected torque profile. Refrigeration systems and compressor systems suitable for implementing the method are also presented.

A screw compressor includes a screw rotor, a gate rotor, and a speed adjuster. The screw rotor has an outer peripheral surface with a plurality of screw grooves. The screw rotor is configured to be rotated. The gate rotor has a plurality of teeth. A ratio T/S of a number T of the teeth to a total number S of the screw grooves is greater than or equal to 2.5. The gate rotor meshes with the screw rotor. The speed adjuster is configured to adjust a rotational speed of the screw rotor. Rotation of the screw rotor at an angle greater than 180° allows the screw compressor to perform a stroke from start of compression to completion of discharge.

A screw compressor includes a screw rotor, a gate rotor, and a speed adjuster. The screw rotor has an outer peripheral surface with a plurality of screw grooves. The screw rotor is configured to be rotated. The gate rotor has a plurality of teeth. A ratio T/S of a number T of the teeth to a total number S of the screw grooves is greater than or equal to 2.5. The gate rotor meshes with the screw rotor. The speed adjuster is configured to adjust a rotational speed of the screw rotor. Rotation of the screw rotor at an angle greater than 180° allows the screw compressor to perform a stroke from start of compression to completion of discharge.

Unique apparatuses, methods, and systems of opposing, limiting, and/or preventing undesired or un-commanded compressor rotation are disclosed. One exemplary embodiment is an HVACR system comprising a variable frequency drive configured to drive an electric motor to rotate a screw compressor or scroll compressor. A controller is configured to monitor various aspects of the system and to control the drive. When a condition indicative of potential undesired or un-commanded compressor rotation is identified, the controller commands the variable frequency drive to control the motor to limit and preferably prevent compressor rotation. One technique comprises shorting switches of the drive to a DC bus rail to allow back EMF induced current in the motor windings to be dissipated through winding resistance thus providing a damping force. Another technique comprises controlling the inverter to insert a DC current into the motor to cause the motor to align to and hold a particular position.

Unique apparatuses, methods, and systems of opposing, limiting, and/or preventing undesired or un-commanded compressor rotation are disclosed. One exemplary embodiment is an HVACR system comprising a variable frequency drive configured to drive an electric motor to rotate a screw compressor or scroll compressor. A controller is configured to monitor various aspects of the system and to control the drive. When a condition indicative of potential undesired or un-commanded compressor rotation is identified, the controller commands the variable frequency drive to control the motor to limit and preferably prevent compressor rotation. One technique comprises shorting switches of the drive to a DC bus rail to allow back EMF induced current in the motor windings to be dissipated through winding resistance thus providing a damping force. Another technique comprises controlling the inverter to insert a DC current into the motor to cause the motor to align to and hold a particular position.

The present disclosure relates to a dual-stage compressor, a control method thereof, and an air conditioning unit. The dual-stage compressor includes a low-pressure stage; a high-pressure stage connected in series with the low-pressure stage; and a volume ratio adjustment mechanism arranged at the high-pressure stage and configured to adjust the volume ratio of refrigerant compression at the high-pressure stage. When the final compression pressure of the compressor is lower or greater than the exhaust pressure, the volume ratio adjustment mechanism is operated to increase or reduce the volume ratio of refrigerant compression at the high-pressure stage so that the final compression pressure of the compressor is equal to the exhaust pressure, and overcompression and undercompression are improved to adapt to changes in external conditions, increase the energy efficiency of the compressor, and reduce the noise of the compressor.

The present disclosure relates to a dual-stage compressor, a control method thereof, and an air conditioning unit. The dual-stage compressor includes a low-pressure stage; a high-pressure stage connected in series with the low-pressure stage; and a volume ratio adjustment mechanism arranged at the high-pressure stage and configured to adjust the volume ratio of refrigerant compression at the high-pressure stage. When the final compression pressure of the compressor is lower or greater than the exhaust pressure, the volume ratio adjustment mechanism is operated to increase or reduce the volume ratio of refrigerant compression at the high-pressure stage so that the final compression pressure of the compressor is equal to the exhaust pressure, and overcompression and undercompression are improved to adapt to changes in external conditions, increase the energy efficiency of the compressor, and reduce the noise of the compressor.

The present disclosure describes a load/unload control method for a compressor system with a rotating compressor connected to a pressure vessel. In the method, the present operating state can be monitored on the basis of a monitored/estimated electrical quantity of the compressor system, The method comprises an identification phase and an operational phase. In the identification phase, the compressor is operated at a constant rotational speed to generate two known pressures to the pressure vessel. At least one electrical quantity is monitored, and values of the electrical quantity corresponding to the pressure limits are stored. In the operational phase, reaching of a pressure limit may then be detected by comparing the present value of the monitored electrical quantity to the stored values.

The present disclosure describes a load/unload control method for a compressor system with a rotating compressor connected to a pressure vessel. In the method, the present operating state can be monitored on the basis of a monitored/estimated electrical quantity of the compressor system, The method comprises an identification phase and an operational phase. In the identification phase, the compressor is operated at a constant rotational speed to generate two known pressures to the pressure vessel. At least one electrical quantity is monitored, and values of the electrical quantity corresponding to the pressure limits are stored. In the operational phase, reaching of a pressure limit may then be detected by comparing the present value of the monitored electrical quantity to the stored values.

A power conversion apparatus includes: an inverter to drive a motor, using a first carrier signal; an inverter connected in parallel to the inverter, to drive a motor, using a second carrier signal; respective phase lower arm shunt resistors to detect a first current flowing inside the inverter; respective phase lower arm shunt resistors to detect a second current flowing in the inverter; and a control unit to control the inverters. A phase difference is set between the first carrier signal and the second carrier signal to prevent a detection period for the first current in the first carrier signal and a detection period for the second current in the second carrier signal from overlapping each other when the inverters are controlled.