Lincoln Electric SVM194-A service manual B3.3, Control of Welding Current

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B3.3				OPERATION		B3.3
Larger machines with a capacity of 350 amperes and					DUTY CYCLE
higher, which are operated at low or no-load conditions					The NEMA output rating of the CLASSIC® 300D KUB-
for extended periods of time are especially susceptible
to the conditions described above. To accomplish suc-					OTA is 300 amperes at 32 arc volts on a 60% duty
cessful engine break-in, most diesel-powered equip-					cycle (consult Specifications in this manual for alternate
ment needs only to be run at a reasonably heavy load					ratings). Duty cycle is based on a ten minute period;
within the rating of the welder for some period of time					thus, the welder can be loaded at rated output for six
during the engineʼs early life. However, if the welder is					minutes out of every ten minute period.
subjected to extensive light loading, occasional moder-					CONTROL OF WELDING CURRENT
ate to heavy loading of the engine may sometimes be
necessary. Caution must be observed in correctly
loading a diesel/generator unit.						CAUTION	-
1. Connect the welder output studs to a suitable					DO NOT TURN THE “CURRENT RANGE SELEC
	resistive load bank. Note that any attempt to short				TOR” WHILE WELDING because the current may
	the output studs by connecting the welding leads				arc between the contacts and damage the switch.
	together, direct shorting of the output studs, or				------------------------------------------------------------------------
	connecting the output leads to a length of steel will				The “Current Range Selector” provides five overlap-
	result in catastrophic damage to the generator and
	voids the warranty.				ping current ranges. The “Fine Current Adjustment”
2. Set the welder controls for an output current and					adjusts the current from minimum to maximum within
	voltage within the welder rating and duty cycle.				each range. Open circuit voltage is also controlled by
	Note that any attempt to exceed the welder rating				the “Fine Current Adjustment” permitting control of the
	or duty cycle for any period of time will result in				arc characteristics.
	catastrophic damage to the generator and voids				A high open circuit voltage setting provides the soft
	the warranty.
3. Periodically shut off the engine and check the					“buttering” arc with best resistance to pop-outs pre-
	crankcase oil level.				ferred for most welding. To get this characteristic, set
					the “Current Range Selector” to the lowest setting that
	WELDER OPERATION				still provides the current you need and set the “Fine
					Current Adjustment” near maximum. For example: to
					obtain 175 amps and a soft arc, set the “Current
				WARNING	Range Selector” to the 190-120 position and then
					adjust the “Fine Current Adjustment” for 175 amps.
		ELECTRIC SHOCK can kill.
		•		Do not touch electrically live parts or	When a forceful “digging” arc is required, usually for
		•		electrode with skin or wet clothing.	vertical and overhead welding, use a higher “Current
				Insulate yourself from work and	Range Selector” setting and lower open circuit voltage.
				ground.	For example:	to obtain 175 amps and a forceful arc,
			FUMES & GASES can be dangerous.		set the “Current Range Selector” to the 240-160 posi-
		• Keep your head out of the fumes.			tion and the “Fine Current Adjustment” setting to get
		• Use ventilation or exhaust to remove			175 amps.
				fumes from breathing zone.	Some arc instability may be experienced with EXX10
					electrodes when trying to operate with long arc tech-
		WELDING SPARKS can cause fire or
					niques at settings at the lower end of the open circuit
		explosion.			voltage range.
		• Keep flammable material away.				CAUTION
		ARC RAYS can burn.			DO NOT attempt to set the “Current Range Selector”
					between the five points designated on the nameplate.
		• Wear eye, ear, and body protection.			------------------------------------------------------------------------
------------------------------------------------------------------------					These switches have a spring loaded cam which
					almost eliminates the possibility of setting this switch
					between the designated points.

CLASSIC® 300D & 300G