AW: Re: Re: Re: [EVGRAY] Oscilloscope problematic.

Hi Gerry, I have extended the shunt a long time ago from a defective 30kw danfoss inverter. I used that for it. Of course it will be more difficult for the scope to measure the low voltage drop. I have grounding points only through the new scope. By the upstream isolating transformer I work earth Potential free if I understand correctly what you mean!?!. The cables are all designed in 6 mm2. I have set up the resonant circuit freely switchable so I can always other components such as transformers, etc. intervene therefore the clamping rails. About a 3-phase 63A switch, I can close the resonant circuit all-pole. Greetings Sven

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-------- Ursprüngliche Nachricht --------
Von: "Gerry [email protected] [EVGRAY]" <[email protected]> 
Datum:17.12.2017  23:24  (GMT+01:00) 
An: [email protected] 
Betreff: Re: Re: Re: [EVGRAY] Oscilloscope problematic. 

Wow Sven,
That's a heavy duty shunt you have there!
The big bolts are to carry the large current under test in and out of the resistor via brass blocks on either end.

The two smaller connections are the voltage measuring points, the resistance is correct between these two points.
It is correct to place your measuring device here, but like me & Ole said.... have to pay attention to your earthing points.

I can see a high current connection to the left end but not the right hand end of the shunt? 
Where does this current come out? 

I don't exactly understand your words in your email above "I still need capacitors for the sheath current filter because I lie partially over 600V, or in series...."

Do you mean the whole shunt is floating at 600V above/below  ground potential?

Sorry... me easily confused

Since shunt is intended for up to 200A and you are only using it at 35A the voltage per amp is going to be quite small.
So  noise and contact potential errors may creep in through dissimilar types of metal at junctions.

I do recommend to try a clip on type ammeter or Hall effect probe for these kinds of measurements.
Gerry.

Here is a link to some other shunt resistors also 
https://www.jaycar.com.au/search?text=current+shunt&CSRFToken=0cf93697-a46e-4fc8-ada7-969a3dc631c3



 




On Sun, Dec 17, 2017 at 10:53 PM, 'Sven Friedrich' [email protected] [EVGRAY] <[email protected]> wrote:


Hi Gerry, I measure at this shunt. The small lines that are led out, I connect to my scope..
I think 200A max. rich for my max. 35 amps in transverter reactive.
I still need capacitors for the sheath current filter because I lie partially over 600V, or in series.

regards

Sven
 
Gesendet: Sonntag, 17. Dezember 2017 um 02:31 Uhr
Von: "[email protected] [EVGRAY]" <[email protected]>
An: [email protected]
Betreff: Re: Aw: Re: [EVGRAY] Oscilloscope problematic.
 
Hi Sven,

Sometimes the high current shunts are 4 terminal resistors.
Usually the two larger terminals are for the current in and out connection.
The actual nominal value of resistance is only correct between the voltage terminals.
Which aren't designed to carry large currents.
 
They are also calibrated in so many nominal mV per Amp rather than Ohms.
 Gerry