Time Current Curve Equations for MCBs

Hi all,

Searching for equations to plot time-current curves for low voltage Type B,C,D MCBs (using Standard values)."
asked 3/31/2012
battler.2
battler.

3 Answers

You may be right and there may be equations. From my reading of the standard it does not appear to be like this; I would could be wrong though.

Before answering yesterday I did some searching and was not able to find anything with equations. For the next couple of weeks I’ll keep the question at the front of my mind, and if I come across anything related to this I’ll post it here.

If you find anything in the meantime, it would be great if you can give feedback as well.
answered 4/2/2012 Steven McFadyen 246
Steven McFadyen
I believe it is possible to plot standard time-current curves based on the limits quoted in the Standards.

There is software which plots these curves with no specific reference to a manufacturer.

I'm trying to find out the method on how this is done.
answered 4/1/2012 battler. 2
battler.
Interesting question. I don’t remember coming across equations and generally look at the curves in the catalogue (or assume my software has the correct curves). The fact that there are ranges, I would interpret as every manufacturer is different and you need to look at their individual curves:

Curve B tripping: 3 to 5 times the rated current (In)
Curve C tripping: 5 to 10 In
Curve D tripping: 10 to 20 In

The actual curve may also vary depending on if you are looking at ac or dc, frequency , etc.

I have also just had a quick flick through the IEC 60898 standard, which gives limits in which the breaker shall operate (for example a C type at 5In should operating between 0.1 and 15 seconds for In<32A), implying that there are no standard curves.
answered 10/4/2011 Steven McFadyen 246
Steven McFadyen

Your Answer

In order to provide an answer to this question, you must Login

I am flagging this question because...




10 inform moderator flags remaining

I am deleting this question because...




I am flagging this answer because...




10 inform moderator flags remaining

Flagging a Post

You have already flagged this post. Clicking "Remove Flag" below will remove your flag, thus reducing the count by one as well.

I am deleting this answer because...





Material Properties

Everything physical in electrical engineering from insulations to conductors revolves around materials. Here we are listing common materials along with...

Low Voltage Circuit Breakers

Circuit breakers are switching devices whose primary function is to isolate parts of an electrical distribution system in the even of abnormal conditions...

Electric Motors

Collection of links to various places with useful motor information. I’ll try and return to the page every now and again to update it with any motor notes...

Battery Sizing

This article gives an introduction to IEEE 485 method for the selection and calculation of battery capacity.

Sony Pocket eBook Reader

For the past few years I have reading eBooks on my HTC touch phone. On and off I have debated buying an eReader and recently purchased a Sony PRS-300 ...

Motor Insulation

Insulation on a motor prevents interconnection of windings and the winding to earth.  When looking at motors, it is important to understand how the insulation...

Alternating Current Circuits

Alternating current (a.c.) is the backbone of modern electrical power distribution. In this article I’ll be pulling some of the more important concepts...

Paths of Flight

GE have put together a time-lapse video shown flight take-off and landings at some airports. An interesting view:

Fire Resistant and Fire Retardant Cables

Fire resistant and fire retardant cable sheaths are design to resist combustion and limit the propagation of flames. Low smokes cables have a sheath designed...

What is Aircraft Ground Power

Ever wondered what kind of power an aircraft uses when parked at the airport stand. Normally the aircraft generates it own power, but when parked with...

Our website uses cookies so that we can provide a better experience.
To learn more about what cookies are and how to manage them visit AboutCookies.org