Tweco 170Pi Transtig - Manual (Page 21)

TRANSTIG 170Pi
Manual 0-5241 3-3 INSTALLATION, OPERATION AND SETUP
bonding the workpiece to earth may reduce emissions in some, but not all instances. Care should be
taken to prevent the earthing of the workpiece increasing the risk of injury to users, or damage to other
electrical equipment. Where necessary, the connection of the workpiece to earth should be made by
direct connection to the workpiece, but in some countries where direct connection is not permitted,
the bonding should be achieved by suitable capacitance, selected according to national regulations.
6. Screening and Shielding
Selective screening and shielding of other cables and equipment in the surrounding area may alleviate
problems of interference. Screening the entire welding installation may be considered for special
applications.
3.06 Transtig 170Pi Power Source Controls, Indicators and Features
A-11645
A-11646
Figure 3-1: Front Panel Figure 3-2: Rear Panel
1. VRD ON/OFF Indicator Lights
A VRD (voltage reduction device) is a hazard reducing device designed to reduce electric shock hazards
present on the output of welding power source when operating in MMAW (stick) mode. Note that the
presence of VRD should not be used as a substitute for the use of appropriate safety practices as indicated
in section one of this manual.
Both the green and red indicator lights only operate in MMAW (stick) mode.
The green VRD ON light illuminates (red light is off) when the VRD is active. Under this condition the open
circuit voltage of the unit is limited to below 10V DC, thus reducing the potential of serious electric shock
(such as when changing electrodes).
The red VRD OFF light illuminates (green light is off) when the VRD is inactive. Under this condition the
output voltage of the unit will be at welding potential which in some cases may exceed 25V DC.
Fail to safe operation
This welding power source is also protected by a special protection feature called “Fail to Safe Operation”
which is available in this model. The output of the power source will be disabled and the fault indicator will
illuminate if the “Fail to Safe” protection has operated.. The “Fail to Safe” protection will not automatically
reset. The mains power switch must be turned off to reset the power source.