Electric heating – Metal heating – By arc
Reexamination Certificate
2001-08-20
2003-01-07
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
By arc
C219S130330, C363S089000
Reexamination Certificate
active
06504132
ABSTRACT:
The invention relates to the art of electric arc welding and more particularly to an electric arc welder having a controlled voltage or current output with the variable or universal AC input that ranges up to about 600 VAC.
INCORPORATION BY REFERENCE
The invention relates to a unique electric arc welder having a dual intermediate stage operated by a power factor control chip whereby a unique architecture allows the input to vary drastically up to 600 volts while the controlled output weld current and/or weld voltage is controlled in the DC welding range. By utilizing the unique architecture of the power factor control dual intermediate stage in combination with an output converter, the power supply for the electric arc welder can have high input voltage variable in magnitude with an output power exceeding two to three kilowatts. Since there are several topographies relating to this type of power supply for use in low rated appliances, several items of prior art are incorporated by reference herein as background information for evaluating uniqueness and superiority of the present invention. The invention relates to power factor correcting power supplies capable of producing a high power rating needed for welding. This feature requires consideration of welding prior art also.
For some time, it has been known to use a boost type power factor correction with an electronic switch controlled by a power factor correcting circuit in the form of a chip. An early version of this architecture is shown in Wilkinson U.S. Pat. No. 4,677,366 which is incorporated by reference for background information. This early power supply does not use the novel architecture of the present invention and can be used for only low power applications.
In Donner U.S. Pat. No. 5,149,933 a boost converter uses a high speed operated switch that can be operated by a power factor controller circuit No. ML 4812 made by Micro-Linear Corporation. This circuit provides a current to a charging capacitor bank throughout the full 180° of each half cycle of the fill wave rectified line voltage. The power factor control chip uses a transformer to apply output energy to the weld operation. This patent appears to be an early laboratory type single phase power supply with a power factor correcting circuit allegedly capable of welding. Current and voltage feedback
1
allegedly controls the pulse generator that operates the switch when there is no power factor control feature used in this early laboratory power supply. This patent discloses background information of an early attempt to use power factor control in a welding installation. Donner U.S. Pat. No. 5,149,933 is incorporated by reference herein as background information only. There is no dual stage inverter, nor output converter.
Since the present invention relates to an architecture wherein a boost converter, albeit a dual stage, drives a DC to DC output converter, Vinciarelli U.S. Pat. No. 5,786,992 is relevant because it shows a related low voltage circuit of this type used for lighting installations. The power factor control is discontinuous whereby input current does not flow at all times. The output power is very limited and the input voltage is fixed at commercial line voltage. This patent does not relates to welding or any other high power technology. However, the patent is incorporated by reference herein merely to show a boost converter for driving a transformer that powers a DC to DC converter using a standard power factor correcting circuit. Such low voltage power factor control circuit for fixed AC input with input voltage less than 220 volts and power ratings less than about 50 watts are somewhat standard at least in the patented technology, but not in practice. Another low power boost circuit with power factor control capabilities is shown in Shikata U.S. Pat. No. 5,917,711 also incorporated by reference. This patent illustrates a boost converter for power factor correction with an output circuit driven by a transformer. The power factor circuit utilizes the input current wave form. This prior low rated power supply can not be used for welding. Turning now to welding power supplies, a power supply circuit having a power factor correcting feature with an output transformer to drive a welding circuit is shown in Moriguchi U.S. Pat. No. 5,864,110. This power supply is used for arc welding; however, it does not have an output stage which allows utilization of a standard DC link that is converted to the necessary welding current and voltage. This patent is incorporated by reference herein.
The Lincoln Electric Company has issued United States patent relating to the use of power factor correcting circuits in various architecture used for electric arc welding. These patents are Kooken U.S. Pat. No. 5,991,169, Church U.S. Pat. No. 6,023,037 and Blankenship U.S. Pat. No. 6,091,612. Each of these power supplies includes power factor correcting feature; however, they do not use the unique architecture for delivery of AC voltage that is converted to a DC link to be converted to low voltage DC use in arc welding. The patents by Lincoln Electric are incorporated by reference herein as background information in that they relate to welding power supplies, but not the architecture of the present invention.
The low power supply circuits constituting the above background information can not be used for welding. Further, those patents incorporated by reference herein that disclose prior attempts to resolve problems associated with electric arc welding use architecture quite different than used in practicing the present invention. All of this background information discloses a body of technology need not be repeated. The specific architecture of the present invention and the novelty thereof is set forth in this disclosure build on or replaces such prior efforts.
The invention utilizes a dual stage boost inverter circuit with power factor correcting capabilities similar to the circuit shown in an article by Wei Batarseh, and Zhu in an article entitled
A Single-Switch AC/DC converter with Power Factor Correction
, dated May 2000. This IEEE article is incorporated by reference herein as background information to explain the operation of the inverter concept for creating the AC output with a controlled power factor for the input. This laboratory type power supply can not be used for welding. The input is less than 220 volts and the power rating is considerably less than 50 watts. This article is incorporated by reference herein as background information.
BACKGROUND OF INVENTION
As indicated by the several prior art patents constituting background, a substantial amount of effort was devoted in the 1980's to develop a power supply for high volume domestic industrial appliances that could be connected to a single phase line voltage and maintain a high power factor or low harmonic distortion. This extensive research and development endeavor was intensified by the need to increase the efficiency and thus reduce the electrical power consumed in large volume by small domestic appliances throughout the nation. These power supplies were designed to use a boost converter, buck converter or flyback converter with specially designed power factor correcting chips using controlled switching of the converter to assure high input power factors and low harmonic distortion. These small power supplies normally created less than 2000 watts of power and were not usable for industrial applications. In the mid 1990's, the electric arc welding industry was using inverter type power supplies with high switching frequency; however, power factor correcting technology for such power supplies did not exist. Consequently, electric arc welders presented a problem with power consumption. There were no techniques to control the power factor of the input lines driving electric arc welders. This was even more pronounced with input that could be as high as 600 VAC.
In the mid 1990's, a few of the companies in the electric arc welding field started experimenting with modifying power factor control
Fay Sharpe Fagan Minnich & McKee
Lincoln Global Inc.
Shaw Clifford C.
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