Tweco 300 MST Arcmaster - Manual (Page 52)

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10.0 VOLTAGE REDUCTION DEVICE (VRD)
10.01 VRD Specification
Description
ARC MASTER
300 MST
Notes
VRD Open Circuit Voltage 15.3 to 19.8V Open circuit voltage between welding terminals.
VRD Resistance 148 to 193 ohms The required resistance between welding
terminals to turn ON the welding power.
VRD Turn OFF Time 0.2 to 0.3 seconds The time taken to turn OFF the welding power
once the welding current has stopped.
10.02 VRD Maintenance
Routine inspection and testing (power source)
An inspection of the power source, an insulation resistance test and an earth resistance test shall be
carried out.
a) For transportable equipment, at least once every 3 months.
b) For fixed equipment, at least once every 12 months.
The owners of the equipment shall keep a suitable record of the periodic tests.
Note 9
A transportable power source is any equipment that is not permanently connected and fixed in
the position in which it is operated.
In addition to the above tests and specifically in relation to the VRD fitted to this machine, the following
periodic tests should also be conducted by an accredited Thermal Arc service agent.
Description IEC 60974-1 Requirements
VRD Open Circuit Voltage Less than 20V; at Vin=230V or 460V
VRD Turn ON Resistance Less than 200 ohms
VRD Turn OFF Time Less than 0.3 seconds
If this equipment is used in a hazardous location or environments with a high risk of electrocution then
the above tests should be carried out prior to entering this location.