Tweco 300 XT Auto-Cut 400V - Manual (Page 120)

AUTO-CUT 300 XT
A-3� APPENDIX Manual 0-5290
The AC Suppression PCB has capacitors and other transient suppression components to protect the system from
transients on the AC lines. It also provides power for the neon AC present indicators which illuminate when AC
power is connected even with ON-OFF switch, CB1, off.
Differences between various models.
Auto-Cut 200 or 300 XT units use the basic gas control/arc start circuits consisting of single gas inlets, one for Plasma,
one for Gas Shield and one for water inlet, optional for AC 200 XT, for H2O Mist shield. There is a pressure regula-
tor and gauge for each gas inlet and water flow meter/control when the H2O Mist option is used. All 3 are turned
on/off with control solenoids. Changing gas types requires connecting different gasses to the rear panel and setting
the gas switch on the rear panel to match the plasma gas type. There is no separate pilot (Preflow) gas at this time.
The Auto-Cut Arc starter is the conventional spark gap type with water cooled coil that we’ve used for several years.
This arc starter injects the HF onto the torch electrode via the negative lead with the return via the tip and pilot lead.
The Ultra-Cut XT units use the remote arc starter, RAS 1000 XT. In place of the spark gap the RAS 1000 XT uses a
solid state ignition module to create the HF pulses which are injected onto the tip and return via the electrode, the
opposite direction of that used in the Auto-Cut, Auto-Cut XT and the older RAS 1000 used with the Ultra-Cut units.
The AC 200 XT had the gas control and arc starter built into the main enclosure in the area that is used for the top
inverter module in other units of this family. The AC 300 XT has a separate gas control/Arc Starter that sits on top
of the main enclosure very similar to the GCM 1000 of our earlier Auto-Cut models. It is in fact called a GCM 1000
XT . Both Auto-Cut XT models have an analog current control (Potentiometer). On the front panel of the main unit
for the AC 200 XT and in the upper box, the GCM 1000 XT, for the AC 300 XT version. In either case the amperage
setting is displayed on the front panel digital display.
Both Auto-Cut models have the gas mode switch on the rear, for the AC 300 XT next to the gas inlets of the GCM
1000 XT. On the AC 200 XT it’s near the connectors, fuses & circuit breakers. The switch should be set according
to the type of gas, AIR/O2 or N2, H35 or other non-oxidizing gas, being used for the plasma.
In the AC 200 XT the Pilot board is mounted on the upper section of the second inverter module (IM#2) the ½ mod-
ule, in the place of the second or “B” section if it was a full module. The AC 300 XT and all Ultra-Cut XT models
have the Pilot board on the opposite side from the inverters, the “circuit breaker” side, in the upper rear behind the
CCM module. Refer to the Replacement Parts section of the manual for illustrations showing the locations.
Ultra-Cut XT units, 100, 200, 300 & 400A units all can use either the GCM 2010 “manual” Gas control or the DFC
3000 Auto Gas Control. These gas controls remain unchanged from earlier Ultra-Cut units.
Ultra-Cut XT units use the same flow switch, FS1, as the Auto-Cut XT units to detect and prevent operation when
coolant flow is below the minimum of 0.75 GPM (2.8 l/m). However, the Ultra-Cut XTs include a coolant flow
sensor, FL1, which also measures the flow and can detect if there are gas bubbles in the coolant which can reduce
consumable part life. Detecting bubbles or low flow from FL1 will NOT prevent cutting but will show a code as a
warning that something is not right. The code is E406.
Ultra-Cut XTs have standard consumables for cutting currents lower than those used for Auto-Cut XT, 15A vs. 55A
as well as marking at lower currents. To improve operation at these lower currents an additional output inductor,
L1, is added in series with the 1st inverter section (IM#1A).