fast reaction circuit breaker

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Post Reply
User avatar
dacflyer
Posts: 4559
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

fast reaction circuit breaker

Post by dacflyer » Tue Feb 10, 2009 6:07 pm

i am working on a project with a winch, light load current draw is 25A , well i had a mishapp the otherday.. the item being pulled got jammed up. and the winch didn;t stop.
i thought well it surely went past the normal max load ( in amps ) so i thought i'd install a circuit breaker.. and i tried (simmulated the overload ) but the breaker didn;t react fast enough, because it is a thermal breaker.. i am looking for something with a faster reaction time,
(non-thermal ) but i have no luck to find what i need.
i am looking for something in the 35 amp range.. thru hole panel mount , push to reset or
bat handle and 12 volts..
i cannot seem to find what i need in digi-key or newark..
does anyone have any other suggestions where i can find such a breaker ?
is there a such animal as an electronic adjustable current breaker?

User avatar
dtief
Posts: 59
Joined: Wed Aug 20, 2008 4:13 pm
Contact:

Re: fast reaction circuit breaker

Post by dtief » Tue Feb 10, 2009 7:37 pm

These are some DC circuit breakers...
http://www.heinemannelectric.com.au/pro ... t.php?p=19

Probably not inexpensive.

Sentron CSA-1V-SO is a current sensor IC. Just rout the wire carrying the current over the IC. Use a comparator to trip (open a relay? or a big FET?) at the desired current.
http://www.sentron.ch/datasheets/CSA-1V.pdf

Might be too fancy - it can be used to measure DC and / or AC to 100KHz.

User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Re: fast reaction circuit breaker

Post by MrAl » Wed Feb 11, 2009 4:54 am

Hi dac,


I would think about building one myself too using perhaps a MOSFET if i had the need to do this.
The only thing to watch out for is to make sure that you have the inductive kickback from
the motor handled effectively or the MOSFET might blow out on the first break.

You should be able to easily get 10us break time using common parts like LM339 or similar
for the comparator. You may have to amplify the current signal using a shunt though.
LEDs vs Bulbs, LEDs are winning.

User avatar
dacflyer
Posts: 4559
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: fast reaction circuit breaker

Post by dacflyer » Wed Feb 11, 2009 7:03 pm

was looking for something off shelf.. prefering a breaker if i could.. i have a few AIRPAX breakers, but nothing that can handle 35 amps.. ( API 8226 / 1-5-2-502 ) thats the number for a 5 amp breaker i have. it has a very fast reaction time.

Bigglez
Posts: 1282
Joined: Mon Oct 15, 2007 7:39 pm
Contact:

Re: fast reaction circuit breaker

Post by Bigglez » Wed Feb 11, 2009 10:42 pm

dacflyer wrote:light load current draw is 25A
...
but the breaker didn;t react fast enough, because it is a thermal breaker.. i am looking for something with a faster reaction time
...
i am looking for something in the 35 amp range
...
is there a such animal as an electronic adjustable current breaker?
Most off the shelf breakers are for higher voltages, and have various
thermal delay overload charactersistics, as you discovered.

For your needs you could force the existing breaker to operate faster
by detecting the fault current and throwing a crow-bar across the
load. It would speed up the existing breaker and brake the motor in
the winch before anything binds up.

You probably won't find one on the shelf, but you can build a small
circuit that monitors the load current and reacts quickly by firing an
SCR (thyristor) that in turn would overload the thermal breaker.
Once the load has been cleared you reset the breaker, the SCR
will clear automatically when the load current reaches zero. A pot
or preset control would allow calibration for you needs.

User avatar
haklesup
Posts: 3046
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Re: fast reaction circuit breaker

Post by haklesup » Thu Feb 12, 2009 1:10 pm

Sounds like you want a thermal/magnetic or magnetic circuit breaker. A quick search on those brought up plenty of hits

Here is one I found on eBay for ~$20
http://cgi.ebay.com/ebaymotors/Blue-Sea ... iesQ5fGear

Note the operating curve. 200% overload trips in about half a second, 125% in 1 second. You may have to derate your current to a lower value to get a faster trip time. You think 35A is about right, the 25A breaker will trip faster at 40A overload. You really need to characterize the start, loaded torque and stall current to select the right value breaker.

Here is the OEM
http://bluesea.com/category/3

User avatar
dacflyer
Posts: 4559
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: fast reaction circuit breaker

Post by dacflyer » Fri Feb 13, 2009 6:18 pm

wow, thanks for that link,.i totally forgot all about bluesea. might be just what i need..

Post Reply

Who is online

Users browsing this forum: No registered users and 31 guests