Excessive load capacitor detection circuit for UPS

• US 6,630,751 B2
• Filed: 03/19/2001
• Issued: 10/07/2003
• Est. Priority Date: 05/13/1999
• Status: Expired due to Term

• Current Assignee: American Power Conversion Corporation (Schneider Electric SE)
• Original Assignee: American Power Conversion Corporation (Schneider Electric SE)
• Inventors: White, Kevin, Paik, Namwook, Reilly, David E., Curtis, Jeffrey
• Primary Examiner(s): Sircus, Brian
• Assistant Examiner(s): RIOS CUEVAS, ROBERTO JOSE
• Application Number:
  US09/811,894
• Publication Number:
  US 20020030411A1
• Time in Patent Office: 932 Days
• Field of Search: 363/132, 363/98, 307/64, 307/66, 307/125, 324/519, 324/548, 324/658, 324/679, 324/680, 324/686
• US Class Current: 307/64
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02M 7/53832 in a push-pull arrangement
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

Embodiments of the present invention are directed to an uninterruptible power supply for providing AC power to a load having a capacitive element. In embodiments of the present invention the uninterruptible power supply includes an input to receive AC power from an AC power source, an output that provides AC power, a DC voltage source that provides DC power, the DC voltage source having an energy storage device, an inverter operatively coupled to the DC voltage source to receive DC power and to provide AC power, the inverter including: first and second output nodes to provide AC power to the load having the first capacitive element, first and second input nodes to receive DC power from the DC voltage source, a circuit operatively coupled to the first output node of the inverter, the circuit being configured to compare a value representative of load capacitance of the first capacitive element with a reference value to determine excessive load capacitance, a set of switches operatively coupled between the first and second output nodes and the first and second input nodes and controlled to generate AC power from the DC power, and a transfer switch constructed and arranged to select one of the AC power source and the DC voltage source as an output power source for the uninterruptible power supply.

Claims

1. An uninterruptible power supply for providing AC power to a load having a first capacitive element, the uninterruptible power supply comprising:

an input to receive AC power from an AC power source;

an output that provides AC power;

a DC voltage source that provides DC power, the DC voltage source having an energy storage device;

an inverter operatively coupled to the DC voltage source to receive DC power and to provide AC power, the inverter including;

first and second output nodes to provide AC power to the load having the first capacitive element;

first and second input nodes to receive DC power from the DC voltage source;

a circuit operatively coupled to the first output node of the inverter, the circuit being configured to compare a value representative of load capacitance of the first capacitive element with a reference value to determine excessive load capacitance;

a set of switches operatively coupled between the first and second output nodes and the first and second input nodes and controlled to generate AC power from the DC power; and

a transfer switch constructed and arranged to select one of the AC power source and the DC voltage source as an output power source for the uninterruptible power supply.

2. The uninterruptible power supply of claim 1, further comprising:

a resonant element having a first terminal and a second terminal, the second terminal being electrically coupled to the first output node of the inverter; and

a switch from the set of switches operatively coupled between the first terminal of the resonant element and the second input node, wherein when the switch is selected, the switch couples the resonant element to the first capacitive element of the load.

3. The uninterruptible power supply of claim 1, wherein the circuit comprises:

a second capacitive element electrically coupled to the first output node to store a voltage of the first capacitive element; and

a logic circuit to compare the stored voltage of the first capacitive element with a reference voltage to determine excessive load capacitance.

4. The uninterruptible power supply of claim 3, wherein the logic circuit includes a microprocessor.

5. The uninterruptible power supply of claim 3, wherein the circuit is configured to store the voltage of the first capactive element during a clamping operation of the inverter.

6. The uninterruptible power supply of claim 2, wherein the circuit comprises:

a comparator having a first input electrically coupled to receive a reference voltage value and a second input electrically coupled to receive a voltage value stored in the first capacitive element when the first switch is selected to coupled the first capacitive element to the resonant element, the comparator configured to continuously compare the first input value with the second input value, the comparator changing a logic state when the second input value exceeds the first input value; and

a logic circuit to measure a time interval between a first time in which the comparator initiates comparison of the first input value with the second input value and a second time in which the second input value exceeds the first input value with a predetermined time interval, the logic circuit determining the load capacitance to be excessive when the time interval exceeds the predetermined time interval.

7. The uninterruptible power supply of claim 6, further comprising:

a first set of resistors coupled to the first input of the comparator to scale the reference voltage value; and

a second set of resistors coupled to the second input of the comparator to scale the first capactive element voltage value, wherein a ratio of the first set of resistors and the second set of resistors determines the value of the second input value with respect to the first input value in which the comparator changes logic state.

8. The uninterruptible power supply of claim 6, wherein the reference voltage is the source voltage.

9. The uninterruptible power supply of claim 6, wherein the logic circuit is a microprocessor.

10. The uninterruptible power supply of claim 1, wherein the circuit is further configured to shutdown the uninterruptible power supply if the circuit determines the load capacitance is excessive.

12. The uninterruptible power supply of claim 10, further comprising:

a resonant element having a first terminal and a second terminal, the second terminal being electrically coupled to the first output node of the inverter; and

a switch from the set of switches operatively coupled between the first terminal of the resonant element and the second input node, wherein when the switch is selected, the switch couples the resonant element to the first capacitive element of the load.

13. The uninterruptible power supply of claim 10, wherein the circuit comprises:

means for comparing including means for comparing the stored voltage of the first capacitive element with a reference voltage to determine excessive load capacitance.

14. The uninterruptible power supply of claim 13, wherein means for comparing includes meaning for shutting down the uninterruptible power if means for comparing determines that the load capacitance is excessive.

11. An uninterruptible power supply for providing AC power to a load having a first capacitive element, the uninterruptible power supply comprising:

an input to receive AC power from an AC power source;

an output that provides AC power;

a DC voltage source that provides DC power, the DC voltage source having an energy storage device;

an inverter operatively coupled to the DC voltage source to receive DC power and to provide AC power, the inverter including;

first and second output nodes to provide AC power to the load having the first capacitive element;

first and second input nodes to receive DC power from the DC voltage source;

means for comparing a value representative of load capacitance of the first capacitive element with a reference value to determine excessive load capacitance;

a set of switches operatively coupled between the first and second output nodes and the first and second input nodes and controlled to generate AC power from the DC power; and

a transfer switch constructed and arranged to select one of the AC power source and the DC voltage source as an output power source for the uninterruptible power supply.