SYSTEM AND METHOD OF CONTROLLING THE START-UP OF AN ADJUSTABLE SPEED MOTOR DRIVE BASED SINUSOIDAL OUTPUT POWER CONDITIONER

• US 20070024231A1
• Filed: 07/26/2005
• Published: 02/01/2007
• Est. Priority Date: 07/26/2005
• Status: Active Grant

• Current Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Lee, Kevin, Wallace, Ian, Doring, Thomas, Ahlgren, Jyrki
• Granted Patent: US 7,468,595 B2
• Time in Patent Office: Days
• US Class Current: 318/802
• CPC Class Codes: H02P 1/04 Means for controlling progress of starting sequence in dependence upon time or upon current, speed, or other motor parameter
• CPC Class Codes: H02P 27/047 V/F converter, wherein the voltage is controlled proportionally with the frequency

Abstract

A motor drive for conditioning power to be delivered to a load includes a current feedback circuit that monitors current being fed to a transformer connected between the motor drive and the load. Based on the total current input to the transformer, a controller adjusts the V/Hz profile along which the motor drive operates. In this regard, the motor drive operates according to a V/Hz profile during start-up that prevents transformer saturation.

Claims

1. A motor drive configured to supply power to a load and, during start-up, supply power to the load according to a given V/Hz profile, the motor drive comprising:

an inverter designed to provide power to a load; and

a controller operationally connected to control operation of the inverter, the controller configured to;

cause the inverter to operate at motor drive start-up according to a default V/Hz profile;

receive feedback of load voltage during motor drive start-up and control operation of the inverter to reduce a difference between load voltage and a desired load voltage;

receive feedback of inverter output current; and

if the inverter output current exceeds a threshold,

cause the inverter to operate according to a new V/Hz profile different from the default V/Hz profile;

otherwise

cause the inverter to operate according to the default V/Hz profile.

2. The motor drive of claim 1 wherein the load is one of a a non-motor load, a motor load, a transformer coupled load, a line voltage and frequency load, a linear load, and a non-linear load.

3. The motor drive of claim 2 wherein the desired load voltage is a fixed voltage and wherein the controller is further configured to control operation of the inverter to provide an output voltage substantially equal to the fixed voltage independent of frequency.

4. The motor drive of claim 1 wherein the new V/Hz profile has less slope than that of the default V/Hz profile.

5. The motor drive of claim 1 connectable to a step-up transformer, and wherein the controller is further configured to adjust operation of the inverter to prevent transformer saturation.

6. The motor drive of claim 1 wherein the inverter is designed to provide an output voltage of at least 370V at 60 Hz during steady-state.

7. The motor drive of claim 6 wherein the default V/Hz profile is 370V/60 Hz.

8. The motor drive of claim 1 wherein the load is a medical imaging scanner.

9. The motor drive of claim 1 wherein the controller includes a PID controller.

10. The motor drive of claim 1 wherein the load is a non-linear load.

11. A power conditioner to supply conditioned power to a load, the power conditioner comprising:

a DC bus;

an inverter connected to the DC bus;

a transformer connected to the inverter and configured to step-up an output of the inverter and provide the stepped-up output to a load; and

a controller that receives feedback of inverter output current and regulates the inverter to prevent current saturation of the transformer during transition of the power conditioner from an initial state to steady-state.

12. The power conditioner of claim 11 wherein the transformer is designed to receive a three-phase input, and further comprising at least three current sensors configured to provide feedback to the controller of inverter output current.

13. The power conditioner of claim 11 wherein the load is one of a non-motor load, a motor load, a transformer coupled load, a line voltage and frequency load, a linear load, and a non-linear load.

14. The power conditioner of claim 11 further comprising an RMS voltmeter designed to provide feedback, in a closed voltage loop, to the controller regarding load voltage, and wherein the controller is further configured to control operation of the inverter to reduce a difference between actual load voltage and a desired load voltage.

15. The power conditioner of claim 11 wherein the inverter includes a plurality of IGBTs and anti-parallel diodes.

16. The power conditioner of claim 11 wherein the controller is further configured to cause the inverter to operate according to a default V/Hz profile during start-up and if inverter output current exceeds a current limit, cause the inverter to operate according to a new V/Hz profile that results in a less rapid rate of change in voltage per Hz than the default V/Hz profile.

17. The power conditioner of claim 11 wherein the controller is further configured to cause the inverter to increase output voltage linearly as a function of frequency.

18. A method of regulating power to a load comprising the steps of:

initially providing power to a load according to a default V/Hz profile;

monitoring output current of an inverter of a motor drive connected to the load; and

causing the inverter to provide power according to a new V/Hz profile if the output current of the inverter exceeds a current limit.

19. The method of claim 18 further comprising the step of receiving feedback of load voltage and controlling the inverter to provide power at a voltage that at least approximates a target output voltage.

20. The method of claim 18 further comprising the step of providing power with a V/Hz profile that has a negative slope if the output current of the inverter exceeds the current limit.

21. The method of claim 18 further comprising the step of dynamically controlling operation of the inverter with a PID controller.

22. The method of claim 18 wherein the motor drive is an ASD motor drive and the load is a non-motor load.

23. The method of claim 22 wherein the non-motor load is a medical imaging scanner.

24. The method of claim 23 wherein the medical imaging scanner is one of a CT scanner and an MR scanner.

25. The method of claim 18 further comprising the step of receiving feedback of load voltage from an RMS voltmeter.