Automatic transfer switch

• US 6,172,432 B1
• Filed: 06/18/1999
• Issued: 01/09/2001
• Est. Priority Date: 06/18/1999
• Status: Expired due to Term

• Current Assignee: Generac Power Systems Incorporated (Generac Holdings Incorporated)
• Original Assignee: Gen-Tran Corporation
• Inventors: Oughton, George, Schnackenberg, Paul
• Primary Examiner(s): Jackson, Stephen W.
• Assistant Examiner(s): RIOS CUEVAS, ROBERTO JOSE
• Application Number:
  US09/335,950
• Time in Patent Office: 571 Days
• Field of Search: 307/125, 307/130, 307/18, 307/64, 307/66, 307/23, 307/24, 307/29, 307/39, 361/166, 361/170, 361/187
• US Class Current: 307/23
• CPC Class Codes: H02J 2310/12 The local stationary network supplying a household or a building
• CPC Class Codes: H02J 3/14 by switching loads on to, or off from, network, e.g. progressively balanced loading
• CPC Class Codes: H02J 9/066 characterised by the use of dynamo-electric machines H02J9/08 takes precedence
• 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: Y02B 70/3225 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y04S 20/222 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y04S 20/242 Home appliances
• CPC Class Codes: Y04S 20/248 UPS systems or standby or emergency generators

Abstract

An automatic transfer switch apparatus for use with a stand-alone generator, for supplying emergency power to a residence or small business. The automatic transfer switch apparatus is configured to sense a utility line failure, start up and stabilize the generator, and switch over the household circuits from the utility to the generator, and switch back when the utility recovers. A load-shedding feature is provided for shedding and restoring different circuits within the residence, that represent loads of different priority, with loads being shed and restored, according to their priority.

Claims

1. An automatic transfer switch apparatus for use in association with a stand-alone generator, for enabling a stand-alone generator to supply electrical power to a plurality of electrical circuits of a structure, such as a residential structure, in the event of failure of electrical power being supplied to the structure by an electrical utility, the automatic transfer switch apparatus comprising:

a plurality of electrical utility inputs, operably configured to be connected to a corresponding plurality of outputs from a residential electrical distribution box, which outputs are connected, at least indirectly, to a utility voltage source;

a plurality of electrical residential outputs, operably configured to be connected to selected ones of specific electrical circuits within the residence;

a plurality of electrical generator inputs, operably configured to be connected to the voltage output of a stand-alone electrical generator;

a plurality of switches, corresponding and connected to respective ones of the plurality of electrical residential outputs, each switch being operably configured for switching between two contact positions, a first contact position connecting at least one electrical residential output to at least one electrical utility input, and a second contact position connecting the at least one electrical residential output to at least one electrical generator input, the switches being actuatable to move from one of the contact positions to the other of the contact positions, upon receipt of an actuation signal;

a controller, operably configured, following installation of the automatic transfer switch, and connection of same to the voltage outputs and starter circuit of a stand-alone generator, to selected ones of the outputs of a residential electrical distribution box, and to the selected ones of the specific electrical circuits of the residence, to detect utility voltage failure, subsequently start the generator, monitor output voltage of the generator, and, upon detection of a minimum nominal output voltage from the generator, and generate actuation signals to cause the switches to move from respective ones of the contact positions to respective others of the contact positions, the controller further being operably configured to transmit actuation signals to corresponding ones of the switches, according to a preselected prioritized hierarchy, corresponding to prioritized ones of the specific electrical circuits of the residence, wherein switches corresponding to higher priority residential electrical circuits will be actuated to connect the generator output to the residential circuit, before switches corresponding to lower priority residential circuits are actuated to connect the generator output to the residential circuit;

the controller further being operably configured to continue to actuate switches corresponding to successively lower priority residential circuits, until total load on the generator exceeds a predetermined maximum load,

the controller further being operably configured to substantially continuously monitor total loading on the generator, de-actuate switches corresponding to lower priority residential circuits, in ascending order of priority, when total load on the generator exceeds a predetermined maximum load, and subsequently reactuate switches corresponding to residential circuits in descending order of priority, when the total load drops below the predetermined maximum load.

2. The automatic transfer switch apparatus according to claim 1, wherein the switches comprise relay switches, which are biased in unactuated first contact positions, connecting electrical residential outputs to electrical utility inputs, and which, upon actuation, are moved to actuated second contact positions, connecting the electrical residential outputs to electrical generator outputs.

3. The automatic transfer switch apparatus according to claim 2, wherein the switches are solenoid-driven relay switches.

4. The automatic transfer switch apparatus according to claim 1, further comprising:

a utility voltage sensor, operably configured to be connected, at least indirectly, to selected ones of the outputs of a residential electrical distribution box,

the selected ones of the outputs of the residential electrical distribution box corresponding to electrical circuits of the residence being designated as having highest priority for supply of electrical power,

the utility voltage sensor being operably configured to transmit a signal to the controller representative of the utility voltage source;

the controller reading and evaluating the level of the signal and deciding, based upon preselected parameters, whether the voltage is acceptable or insufficient.

5. The automatic transfer switch apparatus according to claim 1, further comprising:

a generator voltage sensor, operably configured to be connected, at least indirectly, to the outputs of a generator, for sensing the output voltage of the generator,

the generator voltage sensor being operably configured to transmit a signal to the controller representative of voltage from the generator,

the controller reading and evaluating the level of the signal and deciding, based upon preselected parameters, whether the voltage is acceptable or insufficient.

6. The automatic transfer switch apparatus according to claim 1, further comprising:

a plurality of switch drivers, operably connected to the controller and to the plurality of switches, for successively actuating and deactuating the switches, in accordance to control signals received from the controller.

7. The automatic transfer switch apparatus according to claim 1, further comprising:

a generator load current sensor, operably configured to be connected, at least indirectly, to the electrical generator inputs, for sensing the total load current of the residential circuits on the generator,

the generator load current sensor being operably configured to transmit a signal to the controller representative of generator loading imposed by the residential circuits,

the controller reading and evaluating the signal, and deciding, based upon preselected parameters, whether the loading is acceptable or excessive.

8. The automatic transfer switch apparatus according to claim 1, wherein the controller is further operably configured to automatically exercise the generator at predetermined regular intervals.

9. The automatic transfer switch apparatus according to claim 1, wherein the controller is further operably configured to monitor at least one of total elapsed running time of the generator and total elapsed time from last maintenance, and to provide at least one alarm to an operator to provide maintenance of the generator after a predetermined total elapsed time.

10. The automatic transfer switch apparatus according to claim 1, wherein the controller further comprises:

a display and input panel for enabling an operator to input into programmable memory instructions for a plurality of control parameters,

the display and input panel containing at least one of a plurality of LEDs, an alphanumeric LCD and

at least one of a plurality of pushbuttons, an alphanumeric keypad.

11. The automatic transfer switch apparatus according to claim 1, wherein the controller further comprises:

at least one of non-volatile preprogrammed memory, writable memory for storage of data inputted by an operator, writable memory for storage of data representative of numerical values for electrical conditions sensed by the automatic transfer switch apparatus.