timer controls the length of time that the welding
of control transformer T2 have voltages present at
arc is ON. Normally the preflow purge is not used
all times. Transformer T2 has two secondary wind-
ings, one for 24 volts and one for 230 volts. The 24-
and high frequency is used continuously, When this
timer function is not being used, SPOT ARC switch
volt winding is used primarily to operate the timers
and energize the coil on most of the relays. The 230-
S7 must be set to OFF to disable the timer. When
pre-flow timer M2 is also being used, contacts 1-3 of
volt winding supplies power for the fan, the solenoid
M2 close and apply power to M4 after the preflow
valves, the main contactor, the panel lamps, and the
delay time. The current path for energizing the spot
high voltage transformer. When the POWER switch
arc timer is through normally closed contacts 1-4 of
is off, the 24 volt circuit is interrupted and neither
pilot relay K1. When the pilot relay is energized, the
the 230 volts or the 24 volts activate any circuits, ex-
spot arc timer is disabled due to opened contacts
cept the soft start relays described elsewhere.
1-4 on the relay.
b. Placing the POWER switch in the ON position
c. Post-Flow Timer. The post-flow timer Ml con-
energizes power relay K5. Contacts 6-8 close and
tinues the flow of shielding gas and water after the
s u p p l y holding current to K5 after the POWER
welding arc is broken, to provide protection to the
switch is released. Contacts 1-3 of K5 close and con-
hot tungsten electrode and TIG torch. This timer is
nect 230 vac to the fan motor and POWER indicator
adjusted from 1-30 seconds, depending upon the
lamp DS1. The 230 volts is also applied, through
size of the electrode, the current used, and the time
normally closed contacts 1-4 of the post-flow time'r
required for the tungsten electrode to cool down with-
to GAS-WATER switch S4. If the switch is in the ON
position, GAS-WATER indicator lamp DS2 lights
out oxidizing. The post-flow function should always
be used when TIG welding. When stick electrode
and the gas and the water solenoid valves are ener-
welding, this function is not needed and can be de-
gized. This permits gas and water to appear at the
activated without disturbing the setting on the timer
torch for TIG welding.
by placing the GAS-WATER switch in the OFF posi-
c. To operate the main contactor and apply power
tion. When control relay K6 de-energizes, contacts
to transformer Tl, control relay K6 must he ener-
gized.
8-.5 close and operate the postflow timer. The timer
contacts 1-4 clo s e, keeping water and gas solenoid
d. Assume that CO NTACTOR switch S2 is in the
valve operated for the desired time.
PANEL CONTROL position, causing control relay K6
to be energized, closing contacts 1-3. This applies 230
volts through contacts 6-8 of the pre-flow timer,
a. Power Relay K5. This relay must be energized
through contacts of the spot arc timer and through
to start the welding machine. If the timer drawer
the thermostat to the coil of contactor K8. If the
i n t e r l o c k switch is closed, placing the POWER
CONTACTOR switch is in the REMOTE RECEPT-
switch in the ON position energizes the relay. When
ACLE position, the remote foot control switch must
the POWER switch is released, the contacts are as
be closed to apply 24 volts to the coil of control relay
illustrated in the schematic diagram. Contacts 6-8
K6.
close and supply holding current to keep the relay
e. When main contactor K8 is energized, the ac
energized until the power is removed or until the
power line is connected to the primaries of trans-
POWER switch is placed in the OFF position. When
f o r m e r T1. This transformer supplies the output
K5 is energized, contacts 1-3 are closed and 230 vac
current for welding.
is applied to the fan motor and to POWER indicator
light DS1.
a. Pre-flow Timer M2. This timer is energized when
b. Control Relay K6. After power relay K5 is
control relay K6 is energized. When the timer is
energized, control relay K6 must be energized. This
used, it delays application of 230 volts to the main
is accomplished by closing the CONTACTOR switch
contactor and the high voltage unit. During the de-
lay time, the gas and water solenoid valves are ener-
(PANEL CONTROL position) or closing remote foot
gized. This permits the gas and water to purge the
control switch, which applies 24 vac to the relay.
lines, and permits the gas to purge the work area
Contacts 5-8 of K6 then open, disconnecting power
from the post-flow timer, and contacts 1-3 close. Re-
before the arc is struck. The delay is adjustable from
1 to 30 seconds. At the end of the delay time, contacts
lay K6 contacts 1-3 now permit operation to start,
depending upon the condition of the pre-flow timer
on the timer close and apply power to the contactor
and the spot arc timer.
through contacts of the spot arc timer.
b. Spot Arc Timer. Spot arc timer M4 is used in
c. Main Contactor K8. This coil actuated contactor
applies the ac line voltage to transformer T1 when
conjunction with the proper torch where inert gas-
it is energized. The contactor coil is energized by the
shielded arc spot welding operation is desired. This
