Electric heating – Metal heating – By arc
Reexamination Certificate
2000-10-03
2002-05-07
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
By arc
Reexamination Certificate
active
06384373
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
FIELD OF THE INVENTION
The present invention relates generally to welding power supplies. More specifically, the present invention relates to power circuits for welding power supplies having a supplemental welding power.
BACKGROUND OF THE INVENTION
Welding power supplies are typically stand-alone units which receive a standard line voltage and provide a usable welding power at a welding output. The welding power may be alternating current (AC) or direct current (DC), constant current or constant voltage, three-phase or single-phase, and may include a wide range of amperages, depending upon operator-selected inputs. Various power and control circuitry is used to shape and time the welding power based upon the operator-selected inputs.
Some welding power supplies are preferably configured for both AC and DC welding power applications. These power supplies provide additional versatility to the operator. However, configuring power circuitry for both applications in a single unit is a design challenge.
FIG. 1
illustrates a standard topology of a power circuit for providing a DC welding power. Power circuit
10
includes a transformer
12
for receiving power from AC source
14
and providing it to a bridge rectifier
16
having a plurality of SCRs in a bridge configuration. A control circuit (not shown) provides control signals to the gates of the SCRs. The control signals cause the SCRs to fire in such a way that a full-wave rectified signal is provided. The full-wave rectified signal is provided through an inductor
18
to a weld output
20
, and ultimately to an electrode and workpiece. During some low-power DC welding processes (typically when the output current is
15
amperes or less), the welding power may become discontinuous, which may cause the welding arc to extinguish. Accordingly, a supplemental power source or background circuit
22
is provided. Background circuit receives power from transformer
12
, rectifies the power, filters the power with capacitor
24
, and provides the power as a supplemental power to weld output
20
. The supplemental power helps to maintain the welding arc during the low amperage condition by providing a smooth DC output at approximately 3 Amps that combines with the current from rectifier
16
and inductor
18
.
One drawback of this topology is that a large capacitor
24
is required to smooth the supplemental welding power. Capacitor
24
, typically a large, electrolytic capacitor, is costly.
During an AC configuration, a switch reconfigures the connectors of circuit
10
in such a way that the supplemental power circuit is rendered useless. However, it would be advantageous to provide a supplemental power at inductor
18
during an AC operation to allow for better weld puddle control when welding with an AC squarewave at low currents.
Accordingly, there is a need for a power circuit having a supplemental power source operable during an AC welding operation. Further, there is a need for a simplified supplemental power circuit which provides a supplemental welding power with fewer electrical components than existing topologies. Further still, there is a need for a supplemental power circuit which need not be disabled or enabled based upon the welding operation. The teachings hereinbelow extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above needs.
SUMMARY OF THE INVENTION
According to an exemplary embodiment, a power circuit for a welding power supply includes a control circuit, a power conversion circuit, a filter circuit, and a supplemental power circuit. The control circuit is configured to provide control signals to the power conversion circuit. The power conversion circuit is configured to generate a welding power based on the control signals. The filter circuit is configured to filter the welding power and to provide the filtered welding power at the welding output. The supplemental power circuit is configured to provide a supplemental power. The supplemental power circuit is coupled across the filter circuit such that the filter circuit filters the supplemental power.
According to another exemplary embodiment, a welding power supply includes a transformer, a control circuit, a power conversion circuit, a filter circuit, and a supplemental power circuit. The control circuit is configured to provide control signals. The power conversion circuit is configured to receive an input power from the transformer and to receive the control signals. The power conversion circuit generates an AC welding power at a welding output based on the control signals. The supplemental power circuit is coupled to the filter circuit and is configured to provide a supplemental power to the filter circuit.
According to yet another exemplary embodiment, a method of providing welding power includes providing control signals to a power conversion circuit, generating an AC welding power based on the control signals, generating a supplemental welding power, and providing the supplemental welding power with the AC welding power at a filter device.
REFERENCES:
patent: 2472323 (1949-06-01), Welch, Jr.
patent: 2697160 (1954-12-01), Williams
patent: 4517439 (1985-05-01), Colley
patent: 5218182 (1993-06-01), Vogel et al.
patent: 5683602 (1997-11-01), Stava
Geissler Steven J.
Schwartz Brian A.
Foley & Lardner
Illinois Tool Works
Shaw Clifford C.
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