VRD stands for voltage reduction device. When a MasterWeld VRD 450i is fitted to a welding machine it reduces the maximum unloaded open circuit voltage across the output terminals of the welder to a safe voltage. When a load of less than 200 ohms resistance is applied to the output of the welding machine the VRD will sense this and turn the welder to full output then welding will commence.
Why is this necessary?
A lot of new welders and some older units have an open circuit voltage in excess of 105 volts D.C. or 85 volts a.c. This voltage is currently legal and in normal (dry) conditions may be quite safe.
The only trouble is 95% of sites do not have these normal conditions e.g. (damp or wet, caustic, salty, working at height or in a confined space) an electric shock in these conditions can and has proven fatal. (Ventricular fibrillation, falling from heights and inability to escape the power source when in confined spaces) not to mention the serious physical injuries sustained as a secondary result of an electric shock. Electric shock from a welder power source can also cause serious internal injuries to the human body. These injuries are not always immediately noticeable.
Welding machine insulation levels should be checked regularly. Voltage Reduction Devices are used as an aid in operator safety.
See PDF file for technical spec and further details
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MasterWeld VRD 450i Voltage Reducing Device
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