A compressor for commercial refrigerators comprises an electric motor having a start winding (120) and a run winding (130), in which the input terminals of the start winding (120) and the run winding (130) are connected together and to the line voltage (L), and an electronic start device to supply the start winding (120) during a starting period. The electronic start device comprises a run condenser (40) having a first terminal connected to the output terminal from the start winding (120) and a second terminal connected to the output terminal from the run winding (130), and a start capacitor (45) having a first terminal connected to the output terminal of the start winding (120). In the electronic start device there is also provided a solid state switch (110) which supplies the start winding (120) and is connected between the second terminal of the start capacitor (45) and the neutral terminal of the supply (N), and a control circuit (100) comprising a delay circuit (210, 220) which controls switching of the solid state switch (110) closing it to start the motor and opening it at the end of the starting period once the motor has started.

A dual-drive electric motor control system configured to drive a first electric motor and a second electric motor is provided. The system includes a shared front-end motor drive circuit for converting AC input voltage from an AC voltage source to a DC-link voltage. A first control system has a first inverter coupled to the shared front-end motor drive circuit, and a first switch device configured to couple the AC voltage source directly to the first electric motor. The system further includes a second control system having a second inverter coupled to the shared front-end motor drive circuit, and a second switch device configured to couple the AC voltage source directly to the second electric motor.

A controller and methods for hybrid operation control of an electric motor in an electric motor system are provided. The controller is configured to receive a speed command for operating the electric motor, measure available voltage on an inverter configured to provide conditioned AC voltage to the electric motor, and determine a winding phase angle difference based on the received speed command and the measured available inverter voltage. The controller is also configured to adjust a phase angle difference between winding voltage commands for the switches of the inverter using the determined winding phase angle difference, and apply the winding voltage commands including the adjusted phase angle difference to the inverter switches to control the electric motor.

A controller and methods for hybrid operation control of an electric motor in an electric motor system are provided. The controller is configured to receive a speed command for operating the electric motor, measure available voltage on an inverter configured to provide conditioned AC voltage to the electric motor, and determine a winding phase angle difference based on the received speed command and the measured available inverter voltage. The controller is also configured to adjust a phase angle difference between winding voltage commands for the switches of the inverter using the determined winding phase angle difference, and apply the winding voltage commands including the adjusted phase angle difference to the inverter switches to control the electric motor.

A compressor for commercial refrigerators comprises an electric motor having a start winding (120) and a run winding (130), in which the input terminals of the start winding (120) and the run winding (130) are connected together and to the line voltage (L), and an electronic start device to supply the start winding (120) during a starting period. The electronic start device comprises a run condenser (40) having a first terminal connected to the output terminal from the start winding (120) and a second terminal connected to the output terminal from the run winding (130), and a start capacitor (45) having a first terminal connected to the output terminal of the start winding (120). In the electronic start device there is also provided a solid state switch (110) which supplies the start winding (120) and is connected between the second terminal of the start capacitor (45) and the neutral terminal of the supply (N), and a control circuit (100) comprising a delay circuit (210, 220) which controls switching of the solid state switch (110) closing it to start the motor and opening it at the end of the starting period once the motor has started.

An electric motor system is provided. The electric motor system includes a drive circuit including an inverter configured to supply variable frequency current over a first duration and a switch configured to supply line frequency current over a second duration. The electric motor system further includes an electric motor coupled to the drive circuit and a controller communicatively coupled to the drive circuit. The controller is configured to control the inverter to supply variable frequency current to the electric motor over the first duration, determine to control the drive circuit to transition from supplying variable frequency current to supplying line frequency current, measure at least one parameter of the inverter, compute, based on the at least one measured parameter, an adjustment to a default parameter to enable the inverter to reach a threshold output frequency, and operate the inverter based on the computed adjustment to the default parameter.

An electric motor system is provided. The electric motor system includes a drive circuit including an inverter configured to supply variable frequency current over a first duration and a switch configured to supply line frequency current over a second duration. The electric motor system further includes an electric motor coupled to the drive circuit and a controller communicatively coupled to the drive circuit. The controller is configured to control the inverter to supply variable frequency current to the electric motor over the first duration, determine to control the drive circuit to transition from supplying variable frequency current to supplying line frequency current, measure at least one parameter of the inverter, compute, based on the at least one measured parameter, an adjustment to a default parameter to enable the inverter to reach a threshold output frequency, and operate the inverter based on the computed adjustment to the default parameter.

Hybrid motor drive circuits configured to drive a motor are provided herein. A hybrid motor drive circuit includes an inverter coupled to the motor and configured to drive the motor when a motor commanded frequency is not within a predetermined range of line input power frequencies. The hybrid motor drive circuit also includes a first switch device configured to couple line input power to an output of the inverter when the motor commanded frequency is within the predetermined range of line input power frequencies.

A cooling system is disclosed. The cooling system may have an evaporator, an evaporator fan, a condenser, and at least one compressor. The compressor may be either a single speed or a variable speed compressor. In addition, the system can use a mechanical or electrical pulsed operation refrigerant flow control valve for controlling refrigerant flow to the evaporator.

A cooling system is disclosed. The cooling system may have an evaporator, an evaporator fan, a condenser, and at least one compressor. The compressor may be either a single speed or a variable speed compressor. In addition, the system can use a mechanical or electrical pulsed operation refrigerant flow control valve for controlling refrigerant flow to the evaporator.