US-20260128702-A1 - CONTROLLER AND DRIVE CIRCUIT FOR ELECTRIC MOTORS

US20260128702A1US 20260128702 A1US20260128702 A1US 20260128702A1US-20260128702-A1

Abstract

A controller for an electric motor is provided. The controller includes a processor configured to supply line frequency power to the electric motor through a main switching network, determine to transition from supplying line frequency power to the electric motor to supplying two-phase variable frequency power to the electric motor, synchronize a time base for controlling an output of an inverter with a voltage signal of the line frequency power, open the main switching network to cease supplying line power to the electric motor, and, after a first time period starting from opening the main switching network, supply two-phase variable frequency power to the electric motor using the inverter.

Inventors

Ludovic Andre Chretien
Michael R. Koller

Assignees

REGAL BELOIT AMERICA, INC.

Dates

Publication Date: 20260507
Application Date: 20241104

Claims (20)

1 . A controller for an electric motor, the controller comprising a processor configured to: supply line frequency power to the electric motor through a main switching network; determine to transition from supplying line frequency power to the electric motor to supplying two-phase variable frequency power to the electric motor; synchronize a time base for controlling an output of an inverter with a voltage signal of the line frequency power; open the main switching network to cease supplying line power to the electric motor; and after a first time period starting from opening the main switching network, supply two-phase variable frequency power to the electric motor using the inverter.
2 . The controller of claim 1 , wherein the processor is further configured to dynamically adjust a voltage ratio of the two-phase variable frequency power supplied to the electric motor using the inverter.
3 . The controller of claim 2 , wherein the processor is further configured to dynamically adjust the voltage ratio based on at least one of compressor characteristics, a learning algorithm, or an available bus voltage.
4 . The controller of claim 1 , wherein the processor is further configured to, while supplying two-phase variable frequency power to the electric motor using the inverter, reduce a frequency of the two-phase variable frequency power to a target frequency.
5 . The controller of claim 4 , wherein the frequency of the two-phase variable frequency power is reduced to the target frequency over a second time period at a predefined slew rate.
6 . The controller of claim 1 , wherein the electric motor is a permanent split-capacitor (PSC) electric motor including a main winding and a start winding, and wherein the processor is further configured to electrically couple a capacitor between the main switching network and the start winding using a second switching network when supplying the line frequency power or the two-phase variable frequency power to the electric motor.
7 . The controller of claim 1 , wherein the processor is further configured to compute the first time period based on at least one of a sensed current or an estimated current.
8 . The controller of claim 1 , wherein the electric motor is a permanent magnet (PM) electric motor and line frequency power is only provided to one motor winding at a time.
9 . A method for controlling an electric motor, the method comprising: supplying line frequency power to the electric motor through a main switching network; determining to transition from supplying line frequency power to the electric motor to supplying two-phase variable frequency power to the electric motor; synchronizing a time base for controlling an output of an inverter with a voltage signal of the line frequency power; opening the main switching network to cease supplying line power to the electric motor; and after a first time period starting from opening the main switching network, supply two-phase variable frequency power to the electric motor using the inverter.
10 . The method of claim 9 , further comprising dynamically adjusting a voltage ratio of the two-phase variable frequency power supplied to the electric motor using the inverter.
11 . The method of claim 10 , further comprising dynamically adjusting the voltage ratio based on at least one of compressor characteristics, a learning algorithm, or an available bus voltage.
12 . The method of claim 9 , further comprising, while supplying two-phase variable frequency power to the electric motor using the inverter, reducing a frequency of the two-phase variable frequency power to a target frequency.
13 . The method of claim 12 , wherein the frequency of the two-phase variable frequency power is reduced to the target frequency over a second time period at a predefined slew rate.
14 . The method of claim 9 , wherein the electric motor includes a main winding and a start winding, and wherein the method further comprises electrically coupling a run capacitor between the main switching network and the start winding using a second switching network when supplying the line frequency power or the two-phase variable frequency power to the electric motor.
15 . The method of claim 9 , further comprising computing the first time period based on at least one of a sensed current or an estimated current.
16 . A drive circuit comprising: an electric motor; a main switching network electrically coupled to the electric motor; an inverter electrically coupled to the electric motor; and a processor configured to: supply line frequency power to the electric motor through the main switching network; determine to transition from supplying line frequency power to the electric motor to supplying two-phase variable frequency power to the electric motor; synchronize a time base for controlling an output of the inverter with a voltage signal of the line frequency power; open the main switching network to cease supplying line power to the electric motor; and after a first time period starting from opening the main switching network, supply two-phase variable frequency power to the electric motor using the inverter.
17 . The drive circuit of claim 16 , wherein the processor is further configured to dynamically adjust a voltage ratio of the two-phase variable frequency power supplied to the electric motor using the inverter.
18 . The drive circuit of claim 16 , wherein the processor is further configured to, while supplying two-phase variable frequency power to the electric motor using the inverter, reduce a frequency of the two-phase variable frequency power to a target frequency.
19 . The drive circuit of claim 18 , wherein the frequency of the two-phase variable frequency power is reduced to the target frequency over a second time period at a predefined slew rate.
20 . The drive circuit of claim 16 , wherein the electric motor comprises a permanent split-capacitor (PSC) electric motor comprising a main winding and a start winding, and wherein the processor is further configured to electrically couple a run capacitor between the main switching network and the start winding using a second switching network when supplying the line frequency power or the two-phase variable frequency power to the electric motor.

Description

FIELD The field of the disclosure relates generally to controlling electric motors, and specifically to permanent split-capacitor (PSC) and permanent magnet (PM) electric motors for compressor systems with a mechanism for modulating load on the compressor. BACKGROUND At least some known induction motors are fixed speed motors that operate most efficiently at line frequency power. Such motors exhibit uncontrolled acceleration during startup. Further, at low load conditions, such motors operate less efficiently. Alternatively, some induction motors may be driven with a variable speed motor controller to adapt motor speed to a load level. Such configurations are generally limited by power factor, electromagnetic interference, and electrical losses. A drive circuit for certain motors enables efficient operation at both high and low load conditions. For example, a motor operating a compressor in a heating, ventilation and air conditioning (HVAC) system may experience high load conditions during peak temperatures and low load conditions during milder temperatures. The drive circuit operates the motor using an inverter under low load conditions, and operates the motor using line frequency power under high load conditions. BRIEF DESCRIPTION In one aspect, a controller for an electric motor is provided. The controller includes a processor configured to supply line frequency power to the electric motor through a main switching network, determine to transition from supplying line frequency power to the electric motor to supplying two-phase variable frequency power to the electric motor, synchronize a time base for controlling an output of an inverter with a voltage signal of the line frequency power, open the main switching network to cease supplying line power to the electric motor, and, after a first time period starting from opening the main switching network, supply two-phase variable frequency power to the electric motor using the inverter. In another aspect, a method for controlling an electric motor is provided. The method includes supplying line frequency power to the electric motor through a main switching network, determining to transition from supplying line frequency power to the electric motor to supplying two-phase variable frequency power to the electric motor, synchronizing a time base for controlling an output of an inverter with a voltage signal of the line frequency power, opening the main switching network to cease supplying line power to the electric motor, and, after a first time period starting from opening the main switching network, supply two-phase variable frequency power to the electric motor using the inverter. In another aspect, a drive circuit is provided. The drive circuit includes an electric motor, a main switching network electrically coupled to the electric motor, an inverter electrically coupled to the electric motor, and a processor. The processor is configured to supply line frequency power to the electric motor through the main switching network, determine to transition from supplying line frequency power to the electric motor to supplying two-phase variable frequency power to the electric motor, synchronize a time base for controlling an output of the inverter with a voltage signal of the line frequency power, open the main switching network to cease supplying line power to the electric motor, and after a first time period starting from opening the main switching network, supply two-phase variable frequency power to the electric motor using the inverter. In another aspect, a controller for an electric motor including a first winding and a second winding is provided. The controller includes a processor configured to supply two-phase variable frequency power to the electric motor using an inverter with a run capacitor electrically coupled to one phase of the inverter and to the second winding via a switching network, actuate the switching network to electrically decouple the run capacitor from the second winding, and, after actuating the switching network, supply three-phase variable frequency power to the electric motor. In another aspect, a method for controlling an electric motor including a first winding and a second winding is provided. The method includes supplying two-phase variable frequency power to the electric motor using an inverter with a run capacitor electrically coupled to one phase of the inverter and to the second winding via a switching network, actuating the switching network to electrically decouple the run capacitor from the second winding, and, after actuating the switching network, supplying three-phase variable frequency power to the electric motor. In another aspect, a drive circuit is provided. The drive circuit includes an electric motor including a first winding and a second winding, an inverter electrically coupled to the electric motor, and a processor. The processor is configured to supply two-phase variable frequency power to the electric motor us