Operation - ESAB Heliarc 250 Instruction Manual

SECTION 3
3.1 Control Functions
A. Power On-Off Switch (ROS). In the OFF position,
the power source is electrically shut down; however,
input voltage is still present in the unit (at the input
terminal board and the Power On-Off switch) -- un-
less the customer's line switch is off. In the ON
position, this switch provides power to the fan motor,
the primary and secondary of the main transformer,
and its 115-volt and 24-volt windings to energize the
control circuitry by preparing the ready-to-weld status
of the unit, as determined by the positioning of the
Contactor Control switch TSS (see Item B, following).
B. Tig-Stick Mode Switch (TSS). This 2-position toggle
switch sets the operational modes which can be used.
In the STICK position (with the ROS toggle ON), the
solid-state contactor circuits immediately energize,
and welding power is continuously present at the
output terminals. In the TIG position, the solid-state
contactor and other tig sequencing circuits are con-
trolled by a remote device (foot or torch switch)
through the Remote Control receptacle P17 (see Item
D, following).
C. Current Control (Panel-Remote) Switch (PRS).
This 2-position toggle switch determines the location
from which welding current will be operated; PANEL
position from the power source Weld Current poten-
tiometer, or REMOTE position from an optional foot or
hand control that plugs into the Remote Control re-
ceptacle P17 (see Item D). When the REMOTE
position is selected, the optional remote control will
vary the welding current, but only within the range
preset on the power source Weld Current potentiom-
eter CCP (see Item G).
D. Remote Torch (contactor Receptacle - RTR). The
cable connector from the remote Foot Control or
Torch Switch accessories plugs into this low-voltage
receptacle to control the conducting sequence of the
bridge SCR's to make or break the Tig welding output
power.
E. Remote Control Receptacle (RCC). This recep-
tacle allows you to plug-in a remote accessory (i.e.,
foot or hand control) to provide remote current and/or
contactor control, depending on the Panel/Remote
selection of panel switches described in Items B and
C above.
F. Current Selector Switch (CSS). A 3-position switch
offers a choice of AC, DCSP, or DCRP output current
to suit your particular welding applications. Placing
10
the switch in its DCSP mode causes the output
terminals to assume the following polarities; work is
positive, and torch/electrode is negative. Conversely,
when the switch is in DCRP; work is negative and
torch/electrode is positive. Do not change the posi-
tion of this switch while welding or under load.
G. Current Range Selector Switch (SW1). This 2-
position switch (an integral part of the SCR Control PC
BD.) permits quick coarse selection of the output
current ranges which can be used. The current
ranges are marked (low) 5-60 Amps and (high) 15-
320 Amps. The low range provides exceptional
cleaning action for all low current Tig AC applications.
For higher current Tig welding, always try to select the
appropriate minimum current range that adequately
covers your welding requirements. For Stick elec-
trode welding, position the switch to the desired
current output range. Do not change the position of
this switch while welding or under load.
H. Current Control Potentiometer (CCP). This poten-
tiometer (an integral part of SCR Control PC BD.)
provides fine adjustment of welding current within the
range selected on the Range Switch (SW1). The
panel-faced dial provides an accurate reference for
resetting and/or adjusting the potentiometer.
I. High Frequency (Solenoid) Selector Switch (HFS).
A 3-position toggle switch (an integral part of the Logic
PC BD.) controls high frequency and shielding gas in
the welding operation.
The functional positions are: Off -- no high frequency
and gas solenoid valve is deenergized (this is the
normal position for all stick welding), Continuous --
high frequency and shielding gas are provided through-
out the entire welding cycle (this is the normal position
for all AC Tig welding), and Start -- high frequency
initiates immediately and cuts off when the arc is
established, and the gas solenoid energizes and
remains on throughout the welding cycle (this last
position is normal for most DC Tig welding applica-
tions).
J. Post Flow Control (PFP). This potentiometer (an
integral part of the Logic PC BD.) provides a timed
(from 5 to 45 seconds) post-flow of shielding gas after
the welding arc is broken.
K. Auxiliary 115-Volt Receptacle (J3). This duplex
receptacle can be utilized to source 115-volt power for
auxiliary equipment (grinder, etc.) and is protected by
a 15-amp circuit breaker.
3-1

OPERATION