Welder Current Measurement

kistenr · Nov 28, 2002

I am trying to measure the current on an Meibach Welder at our plant. The welder is used to weld stainless steel coils of max width 1500mm and gauge 2mm. The welder operates intermittently and current values vary across a wide range. I do not know what the exact current values are and what the range is. I was thinking of using a ct to directly measure the current, however this may prove a bit costly, and space constraints prevents this solution. My other idea was to use a shunt and measure volt drop across it and then calculate a current in my plc.

Any comments?

Lewish · Nov 28, 2002

Fluke RMS volt meter with a clamp on current probe. This will give you the RMS value of the current up to about 50KHz. Convenient to use. Quick to connect/disconnect.
Pretty simple.

buzzi · Nov 30, 2002

you could use a amprobe A/C - D/C clamp meter and even read the wire weld current going to the metal your welding if you need to. Or do as the other person suggested and check it on the A/C supply side of the welder, be careful when you do this and if you use the MIN/MAX hold selection, if this is set when you start to weld you will get start (inrush) current as the max and not true welding current Thanks David

electricuwe · Dec 1, 2002

I visited the miebach website (

http://www.miebach.de)

to get some information on the current for such an application. Unfortunately they do not supply technical information on their welders but judging from the application I think you have to expect currents of several 100 kA DC. So the the simple approaches described in former posts will not be suffiecient.

IRstuff · Dec 1, 2002

I think the idea must still be the same, since it's probably foolish and possibly dangerous to try a direct measurement.

The only caveat is the coupling coefficient for the current probe. If the current is indeed that high, you might need to "roll" your own current probe, but building a less efficiently coupled clamp, either through a bigger gap between the conductor and the coil or a skinnier coil.

TTFN

Lewish · Dec 2, 2002

Just keep in mind that most welders of this sophistication use a pulse current and not steady AC or DC. So, you need to take that into consideration in making your measurements. That is why I mentioned the 50KHz capability of the Fluke meter.

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