Abstract:
A self-contained welding power supply capable of, upon termination of welding operation, automatically setting a control signal for auxiliary power is provided. The power supply comprises an engine, a generator driven by the engine, and an excitation system that controls power output of the generator. The excitation system includes an output controller and a DC controller. The output controller includes circuitry that generates a field voltage control signal to be sent to the DC controller to regulate DC power going to field windings of the generator. Upon termination of the welding operation, the field voltage control signal is automatically set to a value appropriate for the auxiliary system operation.

Description:
PRIORITY 
       [0001]    The present application claims priority to U.S. Provisional Patent Application No. 61/943,569, which is incorporated herein by reference in its entirety. 
     
    
     BRIEF SUMMARY OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates in general to equipment used in welding. Devices, systems, and methods consistent with the invention relate to the auxiliary power system in engine-driven welders. 
         [0004]    2. Description of the Related Art 
         [0005]    Welding is an important process in the manufacture and construction of various products and structures. Applications for welding are widespread and used throughout the world, for example, the construction and repair of ships, buildings, bridges, vehicles, and pipe lines, to name a few. Welding may performed in a variety of locations, such as in a factory with a fixed welding operation or on site with a portable welder. For example, welding operations often take place on construction sites, and remote sites, and in other locations where a self-contained power supply is advantageous. 
         [0006]    Self-contained gasoline or diesel fuel welding power supplies are popular products. Such products generally comprise a gasoline or diesel engine that drives an electrical generator having an electrical output, which is used to create an arc and weld metal. Single and three-phase alternating current generators are often used. As these power supplies are used in remote locations, it is often beneficial to have power available for other devices such as lights, appliances, and power tools. Thus, along with providing the welding power output, some related-art self-contained power supplies also provide auxiliary power to power common electrical devices. For example, welders will typically alternate between welding and grinding during the course of a job. Accordingly, a self-contained power supply that supplies both welding power and auxiliary power to auxiliary power receptacles at, e.g., 120 or 240 volts A.C. is beneficial. 
         [0007]    In the related-art systems, the welding voltage and current from the generator is regulated by the amount of field excitation provided to the generator rotor. Because the same generator supplies both welding power and auxiliary power, the excitation controller will also affect the voltage at the auxiliary power receptacles. During many welding operations, full excitation is not needed and thus the excitation controls will be set to less than 100%. However, when welding operations cease and auxiliary power is utilized, e.g., for grinding, the excitation controller must be set to 100% again in order to ensure that full voltage is available to the auxiliary devices such as, e.g., power tools. Repeatedly adjusting the excitation controller when switching between welding operations and utilizing auxiliary power creates a nuisance and the potential for improper welding operations. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    This invention relates to a system or method that is capable of automatically setting a permissible power setting on the auxiliary power output(s) of a welding power supply. For example, the maximum safe power setting on the auxiliary power outlets of an engine-driven welder can be automatically be set when welding operations cease. 
         [0009]    Various aspects will become apparent to those skilled in the art from the following detailed description and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The above and/or other aspects of the invention will be more apparent by describing in detail exemplary embodiments of the invention with reference to the accompanying drawings, in which: 
           [0011]      FIG. 1  is a block diagram of a welding system according to the present invention; 
           [0012]      FIG. 2  is a block diagram of an exemplary embodiment of the exciter in  FIGS. 1 ; and 
           [0013]      FIG. 3  is a schematic diagram of an embodiment consistent with the present invention to set the field voltage input signal. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0014]    Exemplary embodiments of the invention will now be described below by reference to the attached Figures. The described exemplary embodiments are intended to assist the understanding of the invention, and are not intended to limit the scope of the invention in any way. Like reference numerals refer to like elements throughout. 
         [0015]    Referring now to the drawings, there is illustrated in  FIG. 1  a self-contained welding power supply  10 . The welding power supply  10  contains an engine  20 , which can be, e.g., a gasoline engine, diesel engine or some other type of engine, e.g., natural gas/propane. The engine  20  is physically connected to generator  30  via shaft  22 . The generator  30  can be, e.g., a single-phase or three-phase generator. The generator  30  provides power for welding operations through leads  32  to power converter  50 . The power converter  50  receives the AC power from the generator  30  and converts it to the welding voltage and current required by the system. The welding current is sent to the electrode E and workpiece W via leads  52  and  54 . The output of the power converter  50  can include an output reactor  56 . The topology of the power converter is not limiting and can range from simple diode bridges to inverter-based systems. The various topologies of welding power supplies are well-known and will not be further discussed except as needed to describe various embodiments of the present invention. 
         [0016]    The generator  30  also provides auxiliary power to auxiliary power box  60  via line  34 . The auxiliary power box  60  includes auxiliary receptacles  62  and  64  that can be used by power tools, appliances, lighting, etc. As such, the generator  30  is configured to provide the appropriate auxiliary voltage such as e.g., 120 volts A.C. and 240 volts A.C. The receptacles  62  and  64  can be standard receptacles that accept standard power plugs, e.g., 120 and 240 volt A.C. power plugs or can be configured as desired. 
         [0017]    The output of the generator  30  is controlled by the excitation system  40 . The excitation system  40  receives an input signal via line  41  and provides DC power via lead  42  to the generator  30  field windings (not shown) to control the output voltage and current of the generator  30 . The excitation system  40  can be, e.g., a static excitation system in which power is provided by the generator  30  via a stationary device such as a transformer. Of course, the type of excitation system is not limiting and other types of excitation systems can be used as desired, e.g., DC or AC rotating systems in which the excitation power is provided by a small DC or AC generator that is coupled to the same shaft as the generator  30 , or some other power source. 
         [0018]    An exemplary embodiment of an excitation system is illustrated in  FIG. 2 . As seen in  FIG. 2 , the excitation system  40  includes an excitation source  70 , which can be a transformer that is connected to the output of generator  30 . In some embodiments, the excitation source  70  can be integral to generator  30 . The excitation source  70  provides an AC signal that is sent to rectifier system  72 . Rectifier system  72  converts the AC signal from excitation source  70  to a DC signal that is sent to the generator field. The rectifier system  72  can include, e.g., silicon-controlled rectifiers, thyristors, or other appropriate devices that can be controlled so as to regulate the DC power going to the field of generator  30 . By regulating the DC power going to the generator field(s), the welding power and current can be regulated as desired. 
         [0019]    As illustrated in  FIG. 2 , DC controller  74  sends a control signal via line  76  to rectifier system  72  to appropriately control the rectifier system  72  to maintain the desired DC field voltage at the output of the rectifier system  72 . A DC field voltage feedback signal representing the output of the rectifier system  72  can be sent to the DC controller  74  via line  78 . The DC controller  74  receives the desired DC field voltage setpoint from output controller  80 . The DC controller  74  includes the appropriate controls to compare the DC field voltage feedback signal to the desired DC field voltage setpoint and make the appropriate adjustments to the control signal to rectifier system  72 . 
         [0020]    In some embodiments of the present invention, the output controller  80  includes a field voltage input device  82  that can output a desired field voltage control signal V f  to DC controller  74 . In some embodiments, the field voltage input device  82  can be manually set by the welder as desired. For example, in some embodiments as illustrated in  FIG. 2 , the field voltage input device  82  can be a potentiometer that the welder adjusts using an output control knob  81  that is located on, e.g., the welder  10 . Based on the position of the potentiometer, the desired field voltage control signal Vf can range from V fmin  and V fmax . V fmin , based on the value of R 1 , can represent the minimum DC field voltage that can be applied to the generator fields, e.g., based on the generator ratings or some other design criteria. V fmax  can represent the maximum DC field voltage that can be applied to the generator, e.g., based on the generator ratings or some other design criteria. 
         [0021]    During welding operations, the welder can set the field voltage control signal Vf to achieve the desired welding voltage and current. The desired DC field voltage signal V f  is then sent to the DC controller  74 , which compares the setpoint signal V f  to the DC field voltage feedback signal on line  78 . The DC controller  74  will appropriately control the rectifier system  72  so that the desired DC field voltage is sent to the generator field and thus the desired generator welding voltage and current is output for welding operations at electrode E. 
         [0022]    However, when welding operations are stopped, the auxiliary receptacles  62 ,  64 , may not be at the proper voltage because adjusting the field voltage input device  82  during welding operations will also affect the voltage at auxiliary receptacles  61 ,  64 , unless the DC field voltage signal V f  is set back to the proper value for the auxiliary system devices (e.g., back to 100% excitation or some other appropriate value). Thus, in embodiments of the present invention, the DC field voltage signal V f  is automatically set back to a value that is appropriate for auxiliary power operation after welding operations have stopped. For example, in some embodiments, relay  84  with coil  86  and contact  88  can automatically set the DC field voltage signal V f  back to the proper value for the auxiliary system devices after welding operations have stopped. 
         [0023]    For example, coil  86  of relay  84  can be connected across the output reactor  56  as shown in  FIGS. 1 and 2 . When welding operations are being performed, current will flow through the output reactor  56 , and the voltage across the output reactor  56  will build up. When the voltage reaches an upper threshold level, the coil  86  will energize and the normally closed contact  88  will open thereby allowing field voltage input device  82  to function as described above. However, when welding operations are stopped and power converter  50  is turned off, the current through the output reactor  56  will go to zero and the voltage across the reactor  56  with drop to zero. When the voltage drops to a lower threshold level, the coil  86  will de-energize and the normally closed contacts will close and bypass, i.e., short circuit, the field voltage input device  82 . Thus, the voltage corresponding to V fmax  will be sent as the DC field voltage signal V f  to DC controller  74 . Of course, the upper threshold level and the lower threshold levels are set so that welding operations are not adversely affected. That is, when welding operations start, the upper threshold level will be set such that the relay  84  will almost immediate pick up to allow the field voltage input device  82  to be active. The lower threshold is set such that normal voltage fluctuations during the welding process will not inadvertently de-energize relay  84 . 
         [0024]    Of course, other configurations can be used to energize and de-energize relay  84 . For example, the relay  84  control can be based on whether a trigger on the welding torch is depressed. That is, the relay  84  will energize whenever the welder presses the trigger on the welding torch to initiate welding operating, and relay  84  will de-energize whenever the welder releases the trigger to stop welding operations. 
         [0025]    In some embodiments, a voltage other than V fmax  is sent to the DC controller  74  when welding operations have stopped. For example, in  FIG. 3 , one end of the normally closed contact  88  is connected to a predetermined voltage V aux  and a normally open contact  89  is placed in series with field voltage input device  82 . When welding operations have stopped, V aux  is sent as the field voltage input signal V f  to DC controller  74 . When welding operations begin, the normally closed contacts  88  open and normally open contacts  89  close to activate field voltage input device  82 . V aux  can be greater or less than V fmax , depending on the needs of the system. 
         [0026]    In some embodiments of the invention, contacts on the relay  84  can send a welding operations status signal directly to the DC controller  74 . In this embodiment, when welding operations are stopped, the DC controller will ignore field voltage input signal V f  and output a predetermined voltage signal that corresponds to the desired auxiliary voltage. The predetermined voltage signal can be based on a value stored in memory. 
         [0027]    It should be noted that exemplary embodiments of the present invention can be used in either 50 or 60 Hz systems. 
         [0028]    While the invention has been particularly shown and described with reference to exemplary embodiments thereof, the invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the above embodiments.