IDMT query

[SpaceAce7]

I'm sure this is simple.

I was looking through some old books the other day and found some The usual SI, VI, EI and UI were ther but there was also an RI curve.

Can someone tell me what the R stands for?

My best guess is Relatively.

Thanks,

SA7

 

[itsmoked]

Resistance, Current?

 

[DiscoP]

There is an old relay called an RI made by Asea.

Many modern relays have an RI curve setting that emulates this relay's characteristic (eg ABB's SPAJ140).

I don't know what it stands for, but that could be what the book is referring to.

 

[davidbeach]

Really Inverse? ;-)

 

[ctpt]

you can see the following link from ABB. They call these 'RI' Inverse curves. These curves are shown at fig. 39,page 72 of the pdf doc. But it doesn't tell you what RI stands for.

http://library.abb.com/GLOBAL/SCOT/...ent_and_earth-fault_protection_assemblies.pdf

 

[Bung]

As DiscoP syas, it is just the name of the particlar e-m relay that had this particularly strange curve. I don't know that it stands for anything, but if it does it is probably not an English abbreviation. It is one of a family - RI, RIK, RIKS, RIS. It's been around a while - my copy of the instructions is dated 1926 (and has a swastika as the ASEA emblem!).

It has an odd operating principle - the disk spins all the time, and uses a worm drive to close the contacts after pickup. Obvioulsy, the faster the disk spins, the quicker the contacts close!


Bung
Life is non-linear...

 

[mc5w]

Bung,

Sounds like how American highway engineers were at one time using Nazi blueprints and design manuals! Really remarkable how those Nazi's made some technologies happen.