SYSTEM AND METHOD FOR LIMITING LOSSES IN AN UNINTERRUPTIBLE POWER SUPPLY

• US 20100188066A1
• Filed: 01/27/2009
• Published: 07/29/2010
• Est. Priority Date: 01/27/2009
• Status: Active Grant

• Current Assignee: Schneider Electric IT Corporation (Schneider Electric SE)
• Original Assignee: American Power Conversion Corporation (Schneider Electric SE)
• Inventors: Sheng-Hsien, Fang, Deokar, Vishwas Mohaniraj, Paik, Namwook, Rodenhiser, Fred William
• Granted Patent: US 8,212,402 B2
• Time in Patent Office: Days
• US Class Current: 323/302
• CPC Class Codes: H02J 9/00 Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
• CPC Class Codes: H02J 9/062 for AC powered loads

Abstract

Aspects of the invention are directed to systems and method for limiting losses in an uninterruptible power supply. In one aspect, the present invention provides an uninterruptible power supply (UPS) comprising an input to receive input power having an input voltage, an output to provide output power having an output voltage, a neutral line, an automatic voltage regulation (AVR) transformer coupled to the input and the output of the UPS and having an input, an output, a core and at least one switch controllably coupled to at least one of the core, the input and the output, and a means for isolating the core of the AVR transformer from the neutral line when the input voltage is substantially equal to a defined output voltage.

Claims

1. An uninterruptible power supply (UPS) system comprising:

an input to receive input power having an input voltage;

an output to provide output power;

a neutral line;

an automatic voltage regulation (AVR) transformer coupled to the input and the output of the UPS and having an input, an output, a core and at least one switch controllably coupled to at least one of the core, the input and the output;

a bypass switch configured to selectively couple the core of the AVR transformer to the neutral line; and

a controller configured to control the at least one switch of the AVR transformer and the bypass switch,

wherein the controller is configured to control the bypass switch to isolate the core of the AVR transformer from the neutral line in a first mode of operation and to couple the core of the AVR transformer to the neutral line in a second mode of operation.

2. The system of claim 1, wherein the controller is configured to, in the first mode of operation, couple the at least one switch of the AVR transformer to the core and to at least one of the AVR transformer input and the AVR transformer output in a configuration to provide an output voltage of the AVR transformer that is equal to an input voltage of the AVR transformer.

3. The system of claim 2, further comprising a DC voltage source and an inverter coupled to the DC voltage source, wherein the inverter is coupled to the input of the AVR transformer and is configured to provide regulated AC power to the AVR transformer.

4. The system of claim 3, wherein the DC voltage source includes a battery.

5. The system of claim 1, wherein the controller is configured to, in the second mode of operation, couple the at least one switch of the AVR transformer to the core and to at least one of the AVR transformer input and the AVR transformer output in a configuration to provide an output voltage of the AVR transformer that is greater than an input voltage of the AVR transformer by a first ratio.

6. The system of claim 5, wherein the controller is configured, in a third mode of operation, to control the bypass switch to couple the core of the AVR transformer to the neutral line and wherein the controller is further configured to couple the at least one switch of the AVR transformer to the core and to at least one of the AVR transformer input and the AVR transformer output in a configuration to provide an output voltage of the AVR transformer that is greater than the input voltage of the AVR transformer by a second ratio which is larger than the first ratio.

7. The system of claim 6, wherein the second ratio is twice the first ratio.

8. The system of claim 5, wherein the controller is configured, in a fourth mode of operation, to control the bypass switch to couple the core of the AVR transformer to the neutral line and wherein the controller is further configured to couple the at least one switch of the AVR transformer to the core and to at least one of the AVR transformer input and the AVR transformer output in a configuration to provide an output voltage of the AVR transformer that is less than the input voltage of the AVR transformer.

9. The system of claim 1, wherein the bypass switch is an electromagnetic switch.

10. The system of claim 9, wherein the electromagnetic switch is a relay.

11. The system of claim 10, wherein the relay is a single pole double throw relay.

12. The system of claim 10, wherein the relay is a single pole single throw relay.

13. A method of providing stable power in an uninterruptible power supply (UPS) having an automatic voltage regulation (AVR) transformer, an input to receive input power having an input voltage with an AC voltage waveform, an output to provide output power having an output voltage, and a neutral line, the AVR transformer having an input, an output and a core selectively coupled to the neutral line, the method comprising:

determining whether the input voltage to the UPS is within a specified tolerance;

if the input voltage to the UPS satisfies a first condition, isolate the core of the AVR transformer from the neutral line; and

if the input voltage of the UPS satisfies a second condition, couple the core of the AVR transformer to the neutral line.

14. The method of claim 13, further comprising acts of:

configuring the AVR transformer to boost the output voltage of the UPS if the input voltage of the UPS is less than a specified tolerance; and

configuring the AVR transformer to reduce the output voltage of the UPS if the input voltage of the UPS is greater than a specified tolerance.

15. The method of claim 13, wherein the act of isolating comprises an act of decoupling the core of the AVR transformer from the neutral line.

16. The method of claim 13, wherein the AVR transformer includes at least one switch controllably coupled to at least one of the core, the input of the AVR transformer and the output of the AVR transformer, and a bypass switch configured to selectively couple the core of the AVR transformer to the neutral line,

wherein the act of isolating further comprises an act of coupling the at least one switch to the core and one half cycle later, controlling the bypass switch to decouple the core from the neutral line,

wherein the act of coupling the core to the neutral line further comprises an act of controlling the bypass switch to couple the core to the neutral line and one half cycle later, coupling the at least one switch to the core.

17. The method of claim 16, wherein the act of controlling the bypass switch to decouple the core from the neutral line comprises an act of energizing the bypass switch at a zero crossing of the AC voltage waveform,

wherein the act of controlling the bypass switch to couple the core to the neutral line comprises an act of energizing the bypass switch at a zero crossing of the AC voltage waveform.

18. An uninterruptible power supply (UPS) system comprising:

an input to receive input power having an input voltage;

an output to provide output power having an output voltage;

a neutral line;

an automatic voltage regulation (AVR) transformer coupled to the input and the output of the UPS and having an input, an output, a core and at least one switch controllably coupled to at least one of the core, the input and the output; and

means for isolating the core of the AVR transformer from the neutral line when the input voltage is substantially equal to a defined output voltage.

19. The system of claim 18, wherein the at least one switch is selectively coupled, in a first mode of operation, to the core in a configuration to provide an output voltage of the AVR transformer that is equal to an input voltage of the AVR transformer.

20. The system of claim 19, further comprising a DC voltage source coupled to an inverter and wherein the inverter is coupled to the AVR transformer and is configured to provide regulated AC power to the AVR transformer.

21. The system of claim 20, wherein the DC voltage source includes a battery.

22. The system of claim 18, wherein, in a second mode of operation, the core of the AVR transformer is coupled to the neutral line and the at least one switch is selectively coupled to the core in a configuration that results in the output voltage of the AVR transformer being greater than the input voltage of the AVR transformer by a first ratio.

23. The system of claim 18, wherein, in a third mode of operation, the core of the AVR transformer is coupled to the neutral line and the at least one switch is selectively coupled to the core in a configuration that results in the output voltage of AVR transformer to be greater than the input voltage of the AVR transformer by a second ratio which is larger than the first ratio.

24. The system of claim 23, wherein the second ratio is twice the first ratio.

25. The system of claim 18, wherein, in a fourth mode of operation the core of the AVR transformer is coupled to the neutral line and the at least one switch is selectively coupled to the core in a configuration that results in the output voltage of the AVR transformer being smaller than the input voltage of the AVR transformer.