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DC RCDs. Are there any that don't cost several arms..

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Skogsgurra

Skogsgurra

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..and a few legs?

DC distribution systems are coming closer. The once obsolete Edison systems have things going for them and test installations in limited areas are being readied.

One component that we have a hard time finding is a low-cost but reliable ground fault current breaker - aka DC RCD or DC GFCI. Anyone seen any of those? Any development work going on?

Gunnar Englund
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Hi Keith,

The DC voltage is between 280 and 370 V. Fuse is 63 A.

The one I found is quite expensive, 800 - 900 USD (I guess there are reasons for that).

It must operate when fault current is between 15 and 30 mA. Maximum delay is around 100 ms.

Gunnar Englund
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
 
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Yes Keith. That's the one costing a couple of arms - and a leg, too. But only one we found. That you found the same device indicates that there ar few other makes. But we haven't given up yet.

We use it in a demo/test system. Could only afford one. So now we switch off the whole system as soon as someone touches the positive line. Not good. We would like to see much lower prices.

Gunnar Englund
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
 
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Hmmm, If it is just a test system you might make your own??

Or if it is that useful and your demo'd customers might actually feel these would be useful you might work a deal with Bender as you would be providing market exposure/awareness in your market nitch.

Yeah your present system needs someone with really good reflexes always be present - which after a marketing lunch.....

Keith Cress
Flamin Systems, Inc.-
 
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History repeats itself.


If you haven't got that catalogue I'll have a look when I get back to work and get a part number.


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Rolling our own has been discussed. But there are several issues. A few of them are tempco (yes, even with LEM modules, it is an issue) and another one is ability to withstand a 1000+ A short circuit current without getting the magnetics helplessly saturated. Degaussing with DC is possible, but not trivial. Shunts are definitely out - tempco again, and how! (Do the math) Internal power consumption is another thing we have to keep down. No wonder these creatures are difficult to find. And expensive.

Gunnar Englund
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
 
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Maybe you could talk them into making a nonadjustable model with just the features you need.

And/or you could become a distributor.





Mike Halloran
Pembroke Pines, FL, USA
 
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Thanks Scotty. Never thought of Siemens. I ought to, since they are my single largest customer. And I do not find any Siemens DC RCDs how much I ever google. Will contact them Monday - but since they are price leaders, I do not expect a cheap solution.

Interesting to see a thread where Joseph doesn't start an argument. He only points out that he was right all the time :-)

Gunnar Englund
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
 
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Skogs,

These probably make the Bender unit look like bargain of the year but might be of interest. Took a while to find them - they used to be made by Holec before Holec was split up:

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Sometimes I only open my mouth to swap feet...
 
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Hmmm, If it is just a test system you might make your own??

Or if it is that useful and your demo'd customers might actually feel these would be useful you might work a deal with Bender as you would be providing market exposure/awareness in your market nitch.

Yeah your present system needs someone with really good reflexes to always be present - which after a marketing lunch.....
2qu5d3o.gif


Keith Cress
Flamin Systems, Inc.-
 
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Gunnar,
I've been looking internally in Siemens and so far only found the following: the type B is probably not what you are looking for as these are sat on the AC network looking also for the DC component that a type A wouldn't pick up..
I'm in contact with some guys in the ET group to see what's going on, I'll let you know.
 
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Hi sed2,

Re-reading the thread I referenced, it seems that the OP of that thread got confused about the duty a Type B RCD was suited for, then I found him a Type B RCD. The Siemens link states...

Siemens said:
The residual current protective devices of type B are suitable for use in three-phase current systems with 50/60 Hz. On no account may they be used in direct voltage systems or in systems with changing frequencies or frequencies other than 50/60 Hz (e.g. after frequency converters).
Click to expand...

Sorry Gunnar.


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