Electrical transmission or interconnection systems – Plural load circuit systems – Plural sources of supply
Reexamination Certificate
1999-06-18
2001-01-09
Jackson, Stephen W. (Department: 2836)
Electrical transmission or interconnection systems
Plural load circuit systems
Plural sources of supply
C307S064000, C307S125000, C307S029000, C307S039000, C361S170000
Reexamination Certificate
active
06172432
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the technical field of transfer switches, for use with portable or stationary electric generators. In particular, the present invention is directed to an automatic transfer switch apparatus.
2. The Prior Art
Transfer switches, for use in association with portable or stand-alone electrical generators, are known in the prior art.
A private residence, for example, may normally receive its electrical power from a utility company. For various reasons, however (location in a region prone to severe weather, etc.), the homeowner may desire a back-up source of electrical power, so that comfort or at least habitability of the residence can be maintained, during periods in which utility power is unavailable.
Typically, a gasoline, diesel, propane or natural gas internal combustion engine-powered electrical generator, capable of generating split-phase alternating voltage, may be installed in or near the residence, and arranged to be connected to one or more of the electrical circuits in the residence in order to provide the desired back-up power.
However, one cannot simply leave the back-up generator permanently connected, in parallel with the utility power, to the residential electrical circuits, nor can one simply connect and power up a back-up generator, without first disconnecting the residential circuits from the power lines coming in from the utility. The reason for this is the possibility that some of the current generated by the back-up generator may inadvertently be backfed into the utility power lines, which may lead to personal injury and/or damage to utility equipment (transformers, etc.).
Transfer switches have been provided to establish the electrical connections between the utility, the residential circuit(s) and the back-up generator. Prior art residential transfer switches typically have been manually actuated devices; known as “break, then make” switches. This means that when the switch is thrown, the connection between the residential circuit(s) and whichever current source is at the time actually connected to the residential circuit, is broken, before the connection is made between the residential circuit, and the current source which is being substituted in.
In a typical situation, utility power fails or falls drastically. The residence owner proceeds to start up the back-up generator, and once operating speed and voltage have been attained, the switch is manually thrown, to disconnect the utility from the residential circuit, and thereafter, cut in the current from the back-up generator.
Prior art manual transfer switches are capable of providing the simple function of serving to safely accomplish the substitution of power sources. However, such prior art manual switches require the presence of the homeowner, in order to accomplish the transfer. This may be undesirable, in that some appliances (e.g., refrigerator or freezer, sump pump, etc.) should not go without power for extended periods of time. If a homeowner is absent for more than an hour or two, continued power outages may cause potentially serious damage or injury to equipment, property, pets, etc.
Accordingly, it would be desirable to provide a transfer switch for residential/small business environments and the like, that is capable of actuating automatically, upon sensing a sustained interruption of utility-supplied electrical power.
It would also be desirable to provide an automatic transfer switch, that is capable of starting a back-up generator, upon sensing a sustained interruption of utility-supplied electrical power, and disconnecting the utility and connecting the back-up, when the back-up generator is capable of assuming the load.
These and other desirable characteristics of the invention will become apparent in light of the present specification, claims and drawings.
SUMMARY OF THE INVENTION
The present invention is directed to 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 comprises 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 are operably configured to be connected to selected ones of specific electrical circuits within the residence. A plurality of electrical generator inputs are operably configured to be connected to the voltage output of a stand-alone electrical generator.
A plurality of switches are provided, corresponding and connected to respective ones of the plurality of electrical residential outputs. Each switch is 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 is 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 is further 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 is also 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 is further 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.
In a preferred embodiment of the invention, 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. Preferably, the switches are solenoid-driven relay switches.
A utility voltage sensor may be provided which is 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 bo
Oughton George
Schnackenberg Paul
Dick and Harris
Gen-Tran Corporation
Jackson Stephen W.
Rios Roberto
LandOfFree
Automatic transfer switch does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Automatic transfer switch, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Automatic transfer switch will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2520491