Tweco 400 MST Arc Master - Manual (Page 16)

2
INTRODUCTION AND DESCRIPTION
2 – 1
INTRODUCTION AND DESCRIPTION
1
Description
The Thermal Arc™ 400MST is a single & three-phase DC arc welding power source with Constant Current
(CC) and Constant Voltage (CV) output characteristics. This unit is equipped with a Digital Volt/Amperage, lift
arc starter for use with Gas Tungsten Arc Welding (GTAW), Arc Control and Hot Start for Shielded Metal Arc
Welding (SMAW), Inductance Control for Gas Metal Arc Welding (GMAW) processes. The power source is
totally enclosed in an impact resistant, flame resistant and non-conductive plastic case.
Figure 2-1: Model 400MST volt-ampere curve
NOTE
Volt-Ampere curves show the maximum Voltage and Amperage output capabilities of the welding power
source. Curves of other settings will fall between the curves shown.
2
Functional Block Diagrams
Figure 2-2 illustrates the functional block diagram of the 400MST-power supply.
Figure 2-2: 400MST Model functional block diagram
STICK Process LIFT-TIG Process MIG Process
400A 25A (A)
(V)
OCV
10V
400A 5A (A)
(V)
OCV
18V
420A
160A
5A (A)
(V)
OCV
10V
480A
34V
400A
To each control circuit
Main
Circuit
Switch
Filter
Input
Diode
Capacitor
DC Power
Primary
Voltage
Sensor
IGBT
Inverter
Thermal
Detector
Main
Transformers
(T1)
Output
Inductor
Output
Diodes Transformer
(HCT1)
Hall Current
Lift Tig Mode
Output Short
Sensing
Circuit
Stick Mode
VRD
Sensing
Circuit
Thermal
Sensor
Circuit
Drive
Circuit +/-15VDC +18VDC
+24VDC +5VDC
Trouble
Sensing
Circuit
14PIN
Receptacle
(CON1)
Current
Adjustment
Circuit
Reference
Adjustment &
Mode select Switch
Panel Circuit Board
Sequence
Control
Fan Control
Circuit
Fan
Input
Power
Primary
Circuit
Sensor
Down
Transformers
AC115V,AC24V
(T3)
Over
Current
Protect
19PIN
Receptacle
(CON2)
Thermal
Detector
14PIN-19PIN
Select Switch
(S3)