Motor voltage synthesis in reduced voltage soft starters and motor starters employing the same

Patent metadata

Field	Value
Publication number	US-11863091-B2
Application number	US-202217658509-A
Country	US
Kind code	B2
Filing date	Apr 8, 2022
Priority date	Apr 8, 2022
Publication date	Jan 2, 2024
Grant date	Jan 2, 2024

Abstract

A reduced voltage soft starter (RVSS) includes a switching circuit configured to selectively couple an AC power source to a motor and a control circuit configured to sense a line voltage provided to the switching circuit to produce a first voltage signal, to sense a current of the motor to generate a current signal and to generate a second voltage signal representative of a voltage of the motor responsive to the first voltage signal and the current signal. The control circuit may be further configured to generate an estimate of a torque of the motor responsive to the second voltage signal and to control the torque of the motor responsive to the torque estimate.

First claim

What is claimed is:

1. A method of operating a reduced voltage soft starter (RVSS) that drives a motor, the method comprising:
sensing a line voltage provided to the RVSS to produce a first voltage signal;
sensing a current of the motor to generate a current signal;
transforming the first voltage signal according to an ABC-dq0 transformation at a first angle to generate a component signal;
scaling the component signal;
transforming the scaled component signal according to a dq0-ABC transformation at a second angle to generate load-side line-to-neutral voltage signals for respective phases; and
processing the load-side line-to-neutral voltage signals responsive to the current signal to compensate for switching by the RVSS.

2. The method of claim 1 , wherein the current signal comprises respective phase current signals for the respective phases and wherein processing the load-side line-to-neutral voltage signal comprises:
detecting when the phase currents are within detection windows around zero current levels; and
notching the load-side line-to-neutral voltage signals based on the phase currents during the detection windows.

3. The method of claim 1 :
wherein scaling the component signal is preceded by generating a root mean square (RMS) component signal from the component signal;
wherein scaling the component signal comprises scaling the RMS component signal; and
wherein transforming the scaled component signal according to the dq0-ABC transformation comprises transforming the scaled RMS component signal.

4. The method of claim 1 , wherein the first voltage signal represents a line-to-line voltage.

5. The method of claim 1 , further comprising generating an estimate of a torque of the motor responsive to the processed load-side line-to-neutral voltage signals.

6. The method of claim 5 , further comprising controlling the torque of the motor responsive to the torque estimate.

7. The method of claim 6 :
wherein estimating the torque comprises:
generating an instantaneous torque estimate; and
generating an RMS torque estimate from the instantaneous torque estimate; and

wherein controlling the torque comprises controlling the torque responsive to the RMS torque estimate.

8. A method of operating a reduced voltage soft starter (RVSS) that drives a motor, the method comprising:
sensing voltages provided to the RVSS to produce first voltage signals;
sensing phase currents of the motor to generate respective phase current signals for respective phases;
generating respective load-side line-to-neutral voltage signals for the respective phases from the first voltage signals; and
detecting when the phase currents are within detection windows around zero current levels responsive to the phase current signals; and
notching the load-side line-to-neutral voltage signals based on the phase current signals during the detection windows to generate respective notched line-to-neutral voltage signals representative of respective line-to-neutral voltages of the motor.

9. A reduced voltage soft starter (RVSS) comprising:
a switching circuit configured to selectively couple an AC power source to a motor; and
a control circuit configured to sense a line voltage provided to the switching circuit to produce a first voltage signal, to sense a current of the motor to generate a current signal, to transform the first voltage signal according to an ABC-dq0 transformation at a first angle to generate a component signal, to scale the component signal, and to transform the scaled component signal according to a dq0-ABC transformation at a second angle to generate load-side line-to-neutral voltage signals for respective phases; and
wherein the control circuit is configured to generate a second voltage signal by processing the load-side line-to-neutral voltage signals responsive to the current signal to compensate for switching by the switching circuit.

10. The RVSS of claim 9 , wherein the current signal comprises respective phase current signals for the respective phases and wherein the control circuit is configured to detect when the phase currents are within detection windows around zero current levels and to notch the load-side line-to-neutral voltage signals based on the phase currents.

11. The RVSS of claim 9 , wherein the control circuit is configured to generate a root mean square (RMS) component signal from the component signal, to scale the RMS component signal and to transform the scaled RMS component signal according to the dq0-ABC transformation to generate the load-side line-to-neutral voltage signals.

12. The RVSS of claim 9 , wherein the first voltage signal represents a line-to-line voltage.

13. The RVSS of claim 9 , wherein the control circuit is further configured to generate an estimate of a torque of the motor responsive to the second voltage signal.

14. The RVSS of claim 13 , wherein the control circuit is further configured to control the torque of the motor responsive to the torque estimate.

15. The RVSS of claim 14 , wherein the control circuit is configured to generate an instantaneous torque estimate, to generate an RMS torque estimate from the instantaneous torque estimate and to control the torque responsive to the RMS torque estimate.

16. A reduced voltage soft starter (RVSS) comprising:
a switching circuit configured to selectively couple an AC power source to a motor; and
a control circuit configured to sense voltages provided to the RVSS to produce first voltage signals, to sense phase currents of the motor to generate respective phase current signals for respective phases, to generate respective load-side line-to-neutral voltage signals for respective phases, to detect when the phase currents are within detection windows around zero current levels responsive to the phase current signals, and to notch the load-side line-to-neutral voltage signals based on the phase current signals to generate respective notched line-to-neutral voltage signals representative of respective line-to-neutral voltages of the motor.

Assignees

• Eaton Intelligent Power Ltd

Inventors

• Simms Stan Rex

Classifications

• H02P21/34 Primary

  Arrangements for starting · CPC title

• H02P21/20

  Estimation of torque · CPC title

• H02P21/22 Primary

  Current control, e.g. using a current control loop · CPC title

• H02P2207/01

  Asynchronous machines · CPC title

• H02P1/28

  by progressive increase of voltage applied to primary circuit of motor · CPC title