State machine controlled automatic transfer switch system

• US 6,825,578 B2
• Filed: 01/23/2002
• Issued: 11/30/2004
• Est. Priority Date: 01/24/2001
• Status: Expired due to Fees

• Current Assignee: Qaxu Technology, Inc.
• Original Assignee: Qaxu Technology, Inc.
• Inventors: Perttu, Joseph
• Primary Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US10/055,734
• Publication Number:
  US 20020117900A1
• Time in Patent Office: 1,042 Days
• Field of Search: 307/70, 307/64
• US Class Current: 307/70
• CPC Class Codes: H02J 9/06 with automatic change-over , e.g. UPS systems
• CPC Class Codes: H02J 9/068 Electronic means for switching from one power supply to another power supply, e.g. to avoid parallel connection
• CPC Class Codes: H02J 9/08 requiring starting of a prime-mover
• CPC Class Codes: Y02B 70/30 Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
• CPC Class Codes: Y04S 20/20 End-user application control systems

Abstract

An automatic transfer switch system controls switching of power from a main source (utility power) to a backup source (generator) by using a state machine controller and low cost relay switches housed in a single electrical panel. The low power automated transfer switch system is well-suited for residential use and is less expensive and easier to install than conventional automatic transfer switches. The key to a low cost transfer switch is delivering power with low cost relays. This is accomplished by employing relay drive techniques that enable these devices to survive rigorous standards compliance testing. Preferably, the state machine controller measures utility and generator source compliance using an optical coupling arrangement, rather than a transformer. The automated transfer switch disconnects the utility and generator means through a circuit breaker providing for fast protection. The relay drive techniques disclosed provide a form of an electrical interlock. This is a key feature when seeking compliance standard approval. Essentially, an automated transfer system should not continuously be capable of backfeeding power from generator to utility, and the electrical interlock of the relays as taught by this invention prevents any such backfeeding.

Claims

1. A low power automated transfer switch for residential use to automatically switch power between a primary source of utility power and a backup source provided by an engine generator, the automated transfer switch comprising:

a single electrical panel housing;

a first circuit breaker connected to the primary source;

a second circuit breaker connected to the backup source;

at least a third circuit breaker connected to a load;

a pair of first and second electrically interlocked power relays, the first power relay electrically connected between the at least third circuit breaker and the first circuit breaker, and the second power relay electrically connected between the at least third circuit breaker and the second circuit breaker; and

control logic operably connected to the power relays and including a state machine controller to control the option of the power relays to switch from the primary source to the backup source in the event that the control logic detects a decrease in at least one measurable characteristic of the prima source greater than a predetermined value.

2. The low power automated transfer switch of claim 1, wherein the state machine controller is a field programmable gate array (FPGA).

3. The low power automated transfer switch of claim 1, wherein the first circuit breaker and the second circuit breaker are rated for less than 10 kilowatts.

4. The low power automated switch of claim 1, wherein the control logic provides control signals to start and stop the backup source.

5. The low power automated transfer switch of claim 4, wherein the control logic monitors at least one measurable characteristic of the backup source after it is started before switching from the primary source to the backup source.

6. The low power automated transfer switch of claim 1, wherein the control logic monitors the primary source via an optical coupling to detect the at least one measurable characteristics.

7. The low power automated transfer switch of claim 1, further comprising an operator panel positioned on a front of hew electrical panel.

8. The low power automated transfer switch of claim 1, wherein the first and second power relays are configurable to simultaneously be in an open circuit state.

9. The low power automated transfer switch of claim 1, wherein at least one of the first and second power relays includes a relay switch configured as a single throw-type switch.

10. The low power automated transfer switch of claim 1, wherein at least one of the first and second power relays is controlled to perform a switching operation only at phase angles corresponding to about zero phase.

11. A method of connecting a low power automated transfer switch for residential use to automatically switch power between a primary source of utility power and a backup source provided by an engine generator, the method comprising:

providing a single electrical panel for the automated transfer switch;

shutting off power in at least a portion of a main electrical panel that distributes the primary source of utility power within the residence;

wiring a first circuit breaker housed in the electrical panel for the automated transfer switch to a circuit break in the main electrical panel;

wiring a second circuit breaker housed in the electrical panel for the automated transfer switch to a connection on the backup source;

wiring at least a third circuit break housed in the electrical panel for the automated transfer switch to at least one load in the residence; and

turning power back on to the man electrical panel such that the low power automated transfer switch is installed without that power be physically disconnected from the main electrical panel.

12. The method of claim 11, wherein the first circuit breaker and the second circuit breaker are rated for less than 10 kilowatts.

13. The method of claim 11, further comprising:

wiring control signals from control logic housed in the electrical panel to the backup source to start and stop the engine generator.

14. A method of operating a low power automated transfer switch for residential use to automatically switch power between a primary source of utility power and a backup source provided by an engine generator, the method comprising:

providing a single electrical panel for the automated transfer switch, the sine electrical panel housing having;

a first circuit breaker connected to the primary source,

a second circuit breaker connected to the backup source;

at least a third circuit breaker connected to a load; and

a pair of first and second electrically interlocked power relays, the first power relay electrically connected between the at least third circuit breaker and the first circuit breaker, and the second power relay electrically connected between the at least third circuit breaker and the second circuit breaker;

detecting a decrease in at least one measurable characteristic of the primary source; and

in response, using a state machine to automatically control the operation of the power relays to switch from the primary source to the backup source.

15. The method of claim 14, wherein the automatic controlling of the operation of the power relays includes operating the first and second power relays such that both power relays are simultaneously in an open circuit state.

16. The method of claim 14, wherein the providing includes providing at least one of the first and second power relays that includes a relay switch configured as a single throw-type switch.

17. The method of claim 14, wherein the automatic controlling of the operation of the power relays includes operating at least one of the first and second power relays to perform a switching operation only at phase angles corresponding to about zero phase.