WELDING WITH CONSTANT CURRENT
(107 votes)welding equipment
The power source is the heart of all arc welding process. Two basic types of power sources are expressed by their voltage-ampere output characteristics.
The constant current machine is considered in this paragraph. The other power source, the constant voltage machine, is discussed in paragraph 10-3.
The static output characteristic curve produced by both sources is shown in figure 10-1. The characteristic curve of a welding machine is obtained by measuring and plotting the output voltage and the output current while statically loading the machine.
a. The conventional machine is known as the constant current (CC) machine, or the variable voltage type.
The CC machine has the characteristic drooping volt-ampere curve, and has been used for many years for the shielded metal arc welding process.
A constant-current arc-welding machine is one which has means for adjusting the arc current.
It also has a static volt-ampere curve that tends to produce a relatively constant output current.
The arc voltage, at a given welding current, is responsive to the rate at which a consumable electrode is fed into the arc.
When a nonconsumable electrode is used, the arc voltage is responsive to the electrode-to-work distance.
A constant-current arc-welding machine is usually used with welding processes which use manually held electrodes, continuously fed consumable electrodes, or nonconsumable electrodes.
If the arc length varies because of external influences, and slight changes in the arc voltage result, the welding current remains constant.
b. The conventional or constant current (CC) type power source may have direct current or alternating current output.
It is used for the shielded metal-arc welding process, carbon arc welding and gouging, gas tungsten arc welding, and plasma arc welding.
It is used for stud welding and can be used for the continuous wire processes when relatively large electrode wires are used.
c. There are two control systems for constant current welding machines: the single-control machine and the dual-control machine.
(1) The single-control machine has one adjustment which changes the current output from minimum to maximum, which is usually greater than the rated output of the machine.
The characteristic volt-ampere curve is shown by figure 10-2. The shaded area is the normal arc voltage range.
By adjusting the current control, a large number of output curves can be obtained.
The dotted lines show intermediate adjustments of the machine. With tap or plug-in machines, the number of covers will correspond to the number of taps or plug-in combinations available.
Most transformer and transformer-rectifier machines are single-control welding machines.
(2) Dual control machines have both current and voltage controls. They have two adjustments, one for coarse-current control and the other for fine-current control, which also acts as an open-circuit voltage adjustment.
Generator welding machines usually have dual controls. They offer the welder the most flexibility for different welding requirements. These machines inherently have slope control.
f. The constant-current type welding machine can be used for some automatic welding processes. The wire feeder and control must duplicate the motions of the welder to start and maintain an arc. This requires a complex system with feedback from the arc voltage to compensate for changes in the arc length. The constant-current power supplies are rarely used for very small electrode wire welding processes.
www.weldguru.com
These weld controls from Miyachi offer a constant seconday current for increased welding control. AC weld controls and contactors with flexible options.
http://www.tjsnow.com/supplies/miyachi/sec_concurrent.htm
Welding power supply – Wikipedia, the free encyclopedia
Low current can also be used; welding two razor blades together at 5 amps with gas Welding machines are usually classified as constant current (CC) or constant
http://en.wikipedia.org/wiki/Welding_power_supply
Gas tungsten arc welding – Wikipedia, the free encyclopedia
A constant-current welding power supply produces energy which is A negative direct current from the electrode causes a stream of electrons to collide with
http://en.wikipedia.org/wiki/Gas_tungsten_arc_welding
Constant Heat Control for Resistance Welding
Instead of programming current into the welding schedule, “Constant Heat Control (CHC)” algorithm seeks to maintain total weld heat under control.
http://www.weltronic.com/welding_concepts/weldsolutions_chc.html
Gas tungsten arc welding
A constant-current welding power supply produces energy which is A negative direct current from the electrode causes a stream of electrons to collide with
http://schools-wikipedia.org/wp/g/Gas_tungsten_arc_welding.htm
Arc welding: Information from Answers.com
A constant current welding power supply capable of AC and DC Constant voltage, direct current power source is most commonly used with GMAW,
http://www.answers.com/topic/arc-welding
Miller – Selecting a Constant Current (CC) DC Welder for
2. TIG welders that can Stick weld, which have more of a “vertical” constant current output (see Fig. 2) with “drooper” characteristics allow the operator to control weld
http://www.millerwelds.com/resources/articles/index.php?page=article108.html
