Transformers are very robust pieces of machinery if sized and maintained properly. If not and the transformer fails for some reason, the primary voltage could be transmitted into the secondary coil. This is a serious SAFETY situation and a problem for the machine components. Some secondary components in the machine may not be able to handle the higher voltages. People should be safe since they should not be in contact with the weld parts during welding. Hand held guns would be an exception and could be a safety problem.
To alleviate the transformer short and safety problem all machines are designed to have a direct connection to ground. The transformer secondary/machine is normally grounded. In the case of the handheld gun a ground reactor might be a good option to insure safety.
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GROUND REACTOR
The main goal of safety is to detect the sudden high voltage and cause a high current to flow to ground and trip the safety devices (fuse or breaker) which will shut the equipment down.
This Personal safety is provided by having a direct ground on the secondary or a ground reactor or other device as described by ANSI/AWS Z 49.1 Section 12.4.6
Other articles that relate to this subject in this blog are:
WHY DID THE RESISTANCE WELDING TRANSFORMERS SHORT OUT BETWEEN THE PRIMARY AND SECONDARY COILS?
IN WIRE MESH WELDING WHAT INSULATION OR GROUNDING STEPS MIGHT BE TAKEN TO INSURE SAFETY?
References:RWMA – RWMA Resistance Welding Manual 4th Edition
American Welding Society – ANSI/AWS Z 49.1 Sec 12.4.6
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