Electric heating – Metal heating – By arc
Reexamination Certificate
2002-10-11
2004-03-16
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121540
Reexamination Certificate
active
06707001
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to welding systems and, more particularly, to a method and apparatus of voltage protection for use with a welding-type apparatus. Hereinafter, the term “welding-type” shall include welding, cutting, and induction heating devices requiring high power outputs.
Circuit breakers are commonly used in high power environments to protect electrical devices from unexpectedly high voltages. Some circuit breakers take the form of an overvoltage protection control that protects the internal components of an electrical device if the voltage exceeds an acceptable maximum. Typically, the overvoltage threshold is less than the rated maximum of the internal components so as to provide an additional level of protection for the components. Further, notwithstanding the electrical components ability to withstand higher voltages, the maximum allowable or acceptable voltage may be such that any voltage experienced higher than the maximum acceptable voltage yields to unstable environments. The unstable environments may lead to uncontrollable output or excessive heat generation that ultimately affects the instantaneous as well as long term functionality of the device.
Welding-type devices such as plasma cutters used for air plasma cutting and gouging typically implement an overvoltage protection control to protect the internal components of the arc cutting device as well as limit risks associated with unexpectedly high voltages. Typically, arc cutting devices operate on generators or sources with high peak voltage and implement an overvoltage control that detects the peak voltage of a control power winding of the power supply to prevent damage to the internal components of the arc cutting device. However, overvoltage protection based on the peak voltage of a power signal often causes improper operation on generators due to the high peak voltages typically encountered on engine driven power sources. For example, if the maximum acceptable voltage or “trip” voltage is set at 140 volts RMS then the peak voltage for a sinusoidal power signal is typically 198 volts. If, however, the input power signal has a triangular shape, generally true for engine driven generators, the peak voltage must be set for 243 volts to allow operation of the arc cutting device on the 140 volt RMS line. As such, an overvoltage protection based on peak voltage makes it difficult to operate on differing power sources. That is, if the trip voltage is set for operation on a utility line power source, the arc cutting device will not operate properly on a generator. However, if the trip voltage is dependent upon the arc welding device being powered by an engine driven generator, the arc cutting apparatus may experience excessive voltages when operated on a utility line power source.
Therefore, it is desirable to design an overvoltage protection control that enables proper operation of a welding-type device on both a utility line power source as well as a generator with improved variance between the trip voltages associated with each power source.
BRIEF DESCRIPTION OF THE INVENTION
The present invention is directed to an overvoltage protection control overcoming the aforementioned drawbacks. The present invention includes the combination of hardware and software that together detect and determine an average voltage of a power signal being supplied by a power source to a welding-type device. The determined average voltage is then compared to a “trip” voltage. Average voltage can refer either to the arithmetic average of a voltage or the average of the absolute value of that voltage or other statistical quantity. If the average voltage is greater than or equal to the trip voltage then the welding-type device is disabled. The present invention may also be implemented as an undervoltage control wherein the detected average voltage is compared to a minimum acceptable average voltage. In this regard, if the average voltage of the power signal being supplied to the welding-type device is less than the minimum acceptable average voltage, operation of the welding-type device is prevented. As such, the present invention provides an overvoltage/undervoltage protection control.
Therefore, in accordance with one aspect of the present invention, a voltage protection control is configured to detect a voltage of a power signal being supplied to a welding device by a power source. The control is also configured to determine an average of the voltage and compare the average voltage to a trip voltage. The voltage protection control is further configured to output a disabling signal designed to disable the welding device if the average voltage at least equals the trip voltage.
In accordance with another aspect of the present invention, a welding-type apparatus operable on either an engine driven power source or a utility line power source is provided. The welding-type apparatus comprises an enclosure housing a plurality of electrical components including a circuit board. The welding-type apparatus further includes a power cable extending from one end of the enclosure and connectable to the power source. A torch as well as a workpiece holder are provided and each is connected via respective connecting cables to another end of the enclosure. The welding-type apparatus further includes a controller configured to determine an average voltage of a power signal supplied to the plurality of electrical components when the power cable is connected to the power source and prevent operation of the welding-type device if the average voltage is outside an acceptable average voltage range.
In accordance with a further aspect of the present invention, a method of manufacturing the welding-type device operable on either an engine driven power source or a utility line power source is provided. The method includes the steps of providing an enclosure supportable of a plurality of electrical components. The plurality of electrical components includes a circuit board having at least one processor mounted thereto. The method further includes the step of providing at least one electrical path from the power cable to the plurality of electrical components wherein the power cable and the at least one electrical path are configured to translate a power signal from a power source to the plurality of electrical components. The method also includes configuring a processor to determine an average voltage of the power signal and prevent operation of the welding device if the average voltage is outside an acceptable average voltage range.
In accordance with yet a further aspect of the present invention, a computer readable storage medium is provided and includes a computer program stored thereon that represents a set of instructions that when executed by a processor causes the processor to detect an average voltage of a power signal translating power to a welding-type apparatus from a power source. The set of instructions further causes the processor to compare the average voltage to an average voltage range and determine if the average voltage falls outside the average voltage range. If the average voltage falls outside the average voltage range, the set of instructions cause the processor to output a signal designed to disable the welding-type apparatus.
The present invention may also be implemented as a kit to retrofit a welding-type apparatus to trip on an average detected voltage rather than a detected peak voltage or other voltage identifier. Accordingly, the kit includes a circuit board mountable within a housing of the welding-type apparatus. The circuit board includes a microprocessor secured thereto and wired to detect a voltage of a power signal being supplied to the welding-type apparatus by the power source. The microprocessor is further wired to determine an average of the voltage and compare the average to a trip voltage. The microprocessor is further wired to determine if the average of the voltage at least equals the trip voltage and if so, disable the welding-type apparatus.
REFERENCES:
patent: 41031
Schneider Joseph C.
Ulrich James F.
Illinois Tool Works Inc.
Shaw Clifford C.
Ziolkowski Patent Solutions Group LLC
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