Hello so I'm posting to get other peoples thoughts on what we have going on.
I was called to look at why a 3 phase plasma cutter was shocking someone when they touched the weld table to another metal surface in the area. The weld table sits on concrete and isn't grounded to anything. There is a welder on a steel cart on wheels next to weld table and while one person was cutting another person put one hand on table and one on welder cart and felt a good zap.
There is a jib crane near by that connects to steel building if you connect this to the table, shocking no longer happens. So I started to check some stuff with a meter and I see no connection to steel frame of welder to weld table or from table to jib crane reads open line. But I checked DC volts with one lead on table and other on welder cart I get 40-60V DC while plasma cutter is in use then once he stops the voltage slowly drops from 40-60 down to 0 almost looks like it slowly looses a charge. I then checked for current and I only see AC milliamp .30-.40 when using it but no DC current. AC voltages doesn't show anything but maybe a volt or two.
So my thought is its the high frequency of the plasma cutter creating this issue. If we hook a temporary ground to the weld table it should take away the unwanted voltage does that seem correct? I only want the ground to be there while plasma cutting or maybe even tig welding since its high frequency. I have seen regular welders send current back on a table that was grounded with a outlet or something and it will burn the small gauge wire.
I was called to look at why a 3 phase plasma cutter was shocking someone when they touched the weld table to another metal surface in the area. The weld table sits on concrete and isn't grounded to anything. There is a welder on a steel cart on wheels next to weld table and while one person was cutting another person put one hand on table and one on welder cart and felt a good zap.
There is a jib crane near by that connects to steel building if you connect this to the table, shocking no longer happens. So I started to check some stuff with a meter and I see no connection to steel frame of welder to weld table or from table to jib crane reads open line. But I checked DC volts with one lead on table and other on welder cart I get 40-60V DC while plasma cutter is in use then once he stops the voltage slowly drops from 40-60 down to 0 almost looks like it slowly looses a charge. I then checked for current and I only see AC milliamp .30-.40 when using it but no DC current. AC voltages doesn't show anything but maybe a volt or two.
So my thought is its the high frequency of the plasma cutter creating this issue. If we hook a temporary ground to the weld table it should take away the unwanted voltage does that seem correct? I only want the ground to be there while plasma cutting or maybe even tig welding since its high frequency. I have seen regular welders send current back on a table that was grounded with a outlet or something and it will burn the small gauge wire.