Lincoln Electric IM812-A - Manual (Page 18)

B-7 OPERATION B-7
CC (formerly VV) power sources, on the other hand,
permit the arc voltage to decrease with increases in
welding current. The output characteristics of these
power sources can range from a “drooping slope,”
which provide minor arc voltage changes with weld
current variations, to “steep slope” which provide
broad voltage changes with only minor current
variations. The steeper the slope the more difficult it
becomes to maintain arc voltage stability with a
constant wire speed open arc process.
To aid in stabilizing the arc voltage when welding on
CC power sources the LN-35 is provided with a VV
(CC) wire feed mode. This arc voltage sensing feed
mode decreases (or increases) the wire speed when
the arc voltage decreases (or increases).
However , if
the electrode shorts to the work, the arc voltage will
essentially drop to zero and the short circuit current
supplied by the CC power source may not provide
enough power to re-establish the arc (especially with
steeper slope machines). Under this condition the LN-
35 feeder will stop, as if the trigger was released,
and not restart until the short has been opened.
Arc shorting is more difficult to avoid when using
a CC power source, and requires a more refined
operator technique than when using a CV power
source. Improved performance can be obtained
o n C C p o w e r s o u r c e a p p l i c a t i o n s w i t h i n t h e
following guidelines:
1. Flatter slope power sources with higher arc force
(short circuit current) will improve performance
over steep slope machines. The steeper the
slope, the more critical it is to hold proper
electrode stickout to maintain arc stability.
Welding techniques, such as weaving, will be
more difficult to control. Use the highest output
current tap or setting capable of providing the
voltage adjustment required for the procedure.
AUTOMATIC PROTECTION
SHUTDOWN
The LN-35 control provides automatic electronic
protection circuits which shut down the LN-35 for
excessively high power source open circuit voltage or
excessive motor overload.
OVERVOLTAGE SHUTDOWN
If the power source open circuit voltage exceeds about
110-120 volts, the LN-35 will not operate until the
power source voltage drops below about 102-110
volts.
MOTOR OVERLOAD SHUTDOWN
If excessive motor overload occurs (due to prolonged
excessive feeding force, jammed drive rolls or shorted
motor leads), the LN-35 will shut down within a few
seconds after the overload occurs.
The shutdown will reset automatically when the gun
trigger is released, but will reoccur if the overload
situation is not remedied.
LN-35