VARIABLE NEUTRAL IMPEDANCE FOR MULTI-SOURCE SYSTEM

• US 20150130280A1
• Filed: 10/24/2014
• Published: 05/14/2015
• Est. Priority Date: 11/08/2013
• Status: Active Grant

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: O'Reilly, Daniel Patrick, Shipp, David Doyle
• Granted Patent: US 9,917,475 B2
• Time in Patent Office: Days
• US Class Current: 307/65
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: H02J 9/066 characterised by the use of dynamo-electric machines H02J9/08 takes precedence

Abstract

A system includes a first power source and a variable neutral impedance circuit configured to vary a neutral impedance of the first power source based on presence and absence of a parallel coupling of the first power source with a second power source. The variable neutral impedance circuit may be configured to reduce a neutral current of the first power source when the first power source is operating in parallel with the second power source. The variable neutral impedance circuit may include an impedance coupled in series with the first power source, a bypass switch configured to bypass the impedance and a control circuit configured to control the bypass switch. The impedance may include a resistor.

Claims

1. A system comprising:

a first power source; and

a variable neutral impedance circuit configured to vary a neutral impedance of the first power source based on presence and absence of a parallel coupling of the first power source with a second power source.

2. The system of claim 1, wherein the variable neutral impedance circuit is configured to reduce a neutral current of the first power source when the first power source is operating in parallel with the second power source.

3. The system of claim 1, wherein the variable neutral impedance circuit comprises:

an impedance coupled in series with the first power source;

a bypass switch configured to bypass the impedance; and

a control circuit configured to control the bypass switch.

4. The system of claim 3, wherein the impedance comprises a resistor.

5. The system of claim 1, wherein the first and second power sources comprise respective first and second backup generators.

6. The system of claim 5, wherein the first and second generators have different pitches.

7. The system of claim 1, wherein the second power source comprises a utility power source.

11. The system of claim 1, wherein the variable neutral impedance circuit comprises:

an impedance coupled in series with the first generator;

a bypass switch configured to bypass the impedance; and

a control circuit configured to control the bypass switch.

12. The system of claim 11, wherein the impedance comprises a resistor.

8. A system comprising:

a first generator and a second generator configured to be coupled in parallel; and

a variable neutral impedance circuit configured to change a neutral impedance of the first generator responsive to a status of a connection between the first generator and the second generator.

9. The system of claim 8, wherein the variable neutral impedance circuit is configured to provide a first neutral impedance when the first and second generators are operating in parallel and to provide a second neutral impedance when the first generator is operating independently of the second generator.

10. The system of claim 8, wherein the first and second generators comprise respective backup generators configured to provide power in the event of failure of a utility source.

13. The system of claim 8, wherein the first and second generators have different pitches.

14. A method comprising:

providing a first neutral impedance for a first power source when the first power source is operating in parallel with second power source; and

providing a second neutral impedance for the first power source when the first power source is operating independently of the second power source.

15. The method of claim 14, wherein the first neutral impedance is configured to reduce a neutral current of the first power source when the first power source is operating in parallel with the second power source.

16. The method of claim 14:

wherein providing a first neutral impedance for a first power source when the first power source is operating in parallel with second power source comprises providing a circuit component in series with neutral terminal of the first power source and;

wherein providing a second neutral impedance for the first power source when the first power source is operating independently of the second power source comprises bypassing the circuit component.

17. The method of claim 16, wherein the circuit component comprises a resistor.

18. The method of claim 14, wherein the first and second power sources comprise respective first and second backup generators.

19. The method of claim 14, wherein the second power source comprises a utility power source.