CV Mode CURRENT-LIMITING

B-7

OPERATION

B-7

CV MIG and CV Sub-Arc modes employ electronic current limiting to limit excessive short circuit output current which can result in undesirable arc character- istics or nuisance over current protection shutdown (see Machine Protection section).

As shipped, the DC-655 is set for “Hi” current limiting, which maintains constant voltage until the welding current exceeds a level proportional to the voltage set- ting, then falls off linearly at about 10 volts per 100 amps to a limited short circuit current. “Lo” current limiting provides the same short circuit current, but the arc voltage begins to linearly fall off at lower current, at about 5 volts per 100 amps.

“Hi” is recommended for all CV processes, especially for CV subarc and CV arc gouging, but “Lo” tends to “soften” the arc more when welding NR203Ni 1% on the Low Inductance (-) terminal. If “Lo” is desired,

A general guideline for CC welding is to set Arc Force to “Mid” position (#5) and increase (typically no more than to #7) as necessary to prevent “stubbing” or “pop-outs” while welding. This higher Arc Force is rec- commended especially for low end 6010 stick welding.

CC MODE HOT START

Hot start is built-in for CC mode stick and carbon arc starting. Hot Start provides an extra weld current “boost” at the arc strike which increases with higher current settings. This Hot Start level exponentially decays to the weld current setting in a few seconds.

Adjustment of the Hot Start shouldn’t be necessary, but an unsealed trimmer (R81) is provided on the DC- 655 Control PC Board to adjust hot start. Full counter- clockwise adjustment will reduce Hot Start to zero

switch #4(right-most) of the DIP switch located on the lower-center of the DC-655 Control PC board needs to be switched from up (Hi) position to down (Lo) posi- tion.

VOLTS
High
Setting	"HI" Current Limit
	"Lo" Current Limit
Low

CC MODE ARC GOUGING

			Switch #3 is for test
			purposes and is to
DIP Switch			be down

1	2	3		4
1	2	3		4

Switch #4 "Hi"CV Current

Limit (as shown)

CCHot Start Trimmer

Setting

AMPS

CV OUTPUT

CC MODE ARC FORCE

Arc Force provides extra weld current which linearly increases as the welding voltage decreases below a level determined by the constant current setting. The Arc Force control knob, located behind the latched cover, adjust Arc Force from “Min” (no current increase) to “Max” (about 9A/V increase).

VOLTS
OCV
	Hot Start
	Min. Arc Force	Max. Arc Force
	Min. Arc Force
Low	Hi	AMPS
Setting	Hi	AMPS
Setting	Setting
	Setting

CC OUTPUT

Note: See Machine Shutdown section for use of switch #1 and #2.

DC-655 Control PC Board

The DC-655 is rated for air carbon arc gouging with up to 3/8” (10mm) diameter carbons. CC mode goug- ing is often preferred over CV mode for cutting control, but some Arc Force may be required to avoid carbon stubbing.

DC-655