Integrated DC link inductor and common mode current sensor winding

• US 8,373,952 B2
• Filed: 09/29/2006
• Issued: 02/12/2013
• Est. Priority Date: 09/29/2006
• Status: Active Grant

• Current Assignee: Rockwell Automation Technologies Incorporated (Allen-Bradley Co., Inc.)
• Original Assignee: Rockwell Automation Technologies Incorporated (Allen-Bradley Co., Inc.)
• Inventors: Mirafzal, Behrooz, Winterhalter, Craig
• Primary Examiner(s): Barnie, Rexford N
• Assistant Examiner(s): CLARK, CHRISTOPHER JAY
• Application Number:
  US11/541,623
• Publication Number:
  US 20080080106A1
• Time in Patent Office: 2,328 Days
• Field of Search: 361/42, 361/45
• US Class Current: 361/45
• CPC Class Codes: G01R 15/183 using transformers with a magnetic core
• CPC Class Codes: H02M 1/0064 Magnetic structures combining different functions, e.g. storage, filtering or transformation
• CPC Class Codes: H02M 1/12 Arrangements for reducing harmonics from ac input or output
• CPC Class Codes: H02M 1/123 Suppression of common mode voltage or current

Abstract

An integrated DC link inductor and current sensor winding having a core that includes at least two primary legs and at least one secondary leg, two direct current (DC) link windings each wound around one of the two primary legs, and a common mode current sensor winding wound around the secondary leg. Resistors coupled to the common mode current sensor winding may damp the common mode current oscillations.

Claims

1. An apparatus, comprising

a core having at least two primary legs and at least one secondary leg;

two direct current (DC) link windings each wrapped around one of the two primary legs;

a current sensor winding wrapped around the secondary leg, wherein the current sensor winding conducts a common mode current generated by a difference in currents flowing in different directions in the two DC link windings; and

a rectifier, wherein the rectifier is configured to rectify the common mode current of the current sensor winding.

2. The apparatus of claim 1, wherein the two DC link windings are configured to substantially prevent magnetic flux of differential mode currents from penetrating the secondary leg.

3. The apparatus of claim 1, wherein the two primary legs each comprise a gap and the secondary leg does not have a gap.

4. The apparatus of claim 3, wherein the core is configured to conduct magnetic flux from the differential mode current through the gap in both of the primary legs and magnetic flux from a common mode current through the gap in one of the primary legs but not through the gap in the other primary leg.

5. The apparatus of claim 4, comprising:

a damping resistor in series with the current sensor winding;

a second resistor in series with both the current sensor winding and the damping resistor; and

a ground fault detector coupled to the second resistor.

8. The apparatus of claim 5, wherein the damping resistor is configured to increase the damping factor for common mode current and reduce electromagnetic emission.

6. An apparatus, comprising

a core having at least two primary legs and at least one secondary leg, wherein the two primary legs each comprise a gap and the secondary leg does not have a gap;

two direct current (DC) link windings each wrapped around one of the two primary legs;

a current sensor winding wrapped around the secondary leg, wherein the current sensor winding conducts a common mode current generated by a difference in currents flowing in different directions in the two DC link windings, wherein the core is configured to conduct magnetic flux from the differential mode current through the gap in both of the primary legs and magnetic flux from a common mode current through the gap in one of the primary legs but not through the gap in the other primary leg;

a damping resistor in series with the current sensor winding;

a second resistor in series with both the current sensor winding and the damping resistor;

a ground fault detector coupled to the second resistor; and

a rectifier, wherein the second resistor is coupled to the current sensor winding through the rectifier.

7. The apparatus of claim 6, wherein the damping resistor is disposed in series with the current sensor winding and the rectifier.

9. A method, comprising:

receiving, in a core, magnetic flux induced by differential mode currents in a positive current path and a negative current path through a DC link, wherein current in the positive current path flows in a different direction from current in the negative current path;

receiving, in the core, resultant magnetic flux induced by a common mode current in the DC link, wherein the common mode current corresponds to a difference between magnitudes of the differential mode currents; and

sensing the resultant magnetic flux;

inducing a current in a common mode current sensor winding from the resultant magnetic flux; and

rectifying the current via a rectifier to generate a rectified current.

10. The method of claim 9, wherein the induced current is proportional to the common mode current in the DC link, and wherein the resultant magnetic flux is received in a secondary leg of the core.

11. The method of claim 10, comprising:

measuring the rectified current;

determining whether a ground fault has occurred based on the measurement; and

opening the positive current path, the negative current path, or both in response to a determination that a ground fault has occurred.

12. The method of claim 10, comprising determining a parameter of a load based on a direction of the resulting magnetic flux, a magnitude of the resulting magnetic flux, a rate of change of one or more of these parameters, or a combination thereof.

13. The method of claim 9, comprising:

conducting DC power that is flowing between a power supply and a load; and

sensing a ground fault.

14. The method of claim 13, comprising damping oscillations of the common mode current and suppressing electromagnetic interference.

21. The method of claim 9, comprising sensing by a current sensor comprising the rectifier, saturation of the core by the common mode current.

15. A method, comprising:

disposing a pair of DC link inductor windings about a common core; and

disposing a winding of a common mode current sensor about the common core, wherein the current mode sensor monitors a rectified common mode current generated by rectifying a difference in currents flowing in different directions in the pair of DC link windings.

16. The method of claim 15, comprising coupling the winding of the common mode current sensor to a common mode current sensor, wherein the common mode current sensor comprises a ground fault detector.

17. The method of claim 15, wherein the common core comprises two primary legs about which the pair of DC link inductor windings are respectively disposed and a secondary leg about which the winding of the common mode current sensor is disposed.

18. The method of claim 15, comprising disposing the pair of DC link inductor windings in a power conversion system.

19. The method of claim 18, comprising coupling the power conversion system to an AC motor, a generator, or a combination thereof

20. The method of claim 15, wherein the common mode current sensor comprises a controller configured to detect a ground fault and open a current path that includes one of the DC link inductors in response to the ground fault.

22. The method of claim 16, comprising coupling a rectifier, via a resistor, to the winding of the common mode current sensor to rectify the difference in currents flowing in different directions in the pair of DC link windings for preventing saturation of the core by a common mode current.