Help me solve a fuse failing problem in a standalone charger

[chanchal.chauhan]

Dear ALL,

We have AC/DC & DC/DC section in our project. Presently in DC-DC section Fuse is falling.
We have used initially AC fuse 5 Amps & that is falling. But know we have changed the i/p fuse 5 Amps to 10 Amps know o/p fuse is falling. O/p fuse is 15 Amps.

I want to know why fuse is falling & there root cause?
Any help is greatly appreciated?

Thanks & Regards
Chanchal Chauhan

 

[srizbf]

Re: Fuse Faling

without knowing what kind of load your supply sees , it cannot be inferred why your fuse is blowing off.

ac/dc and dc/dc is not sufficient information.

does the fuse blowoff when you switchon or when it is operating ?
give more info.

srizbf
24thmay2010

 

[dick_freebird]

Fuse Faling

Fuses cannot be operated indefinitely, anywhere near their
rated interrupt current. They will electromigrate open faster as
you approach the blow threshold.

Start with measuring the real steady and surge currents,
which latter ought to be pretty big unless soft start is set up
right, and dig up some fuse application guidelines to select the
right value based on that.

 

[chanchal.chauhan]

Re: Fuse Faling

Here Load is 60AH Lead Acid Battery. Here DC Fuse is falling while charging the battery & its happening once in a week.



Regards,
Chanchal

 

[srizbf]

Re: Fuse Faling

is it a standalone charger for the leadacid battery?

(or) the battery is connected to charger and also to any other load ?

srizbf
25thmay2010

 

[IanP]

Re: Fuse Faling

Finding the right size of the fuse shouldn't be a guess work ..
Measure the charging current and select a fuse about two times the maximum current you are charging with ..
This fuse is not to protect the supply from a short in the charger, but to protect everything else from the battery in case of a short anywhere ..

IanP

 

[chanchal.chauhan]

Re: Fuse Faling

Yah it is a standalone charger.
Load is here only battery.

 

[srizbf]

Re: Fuse Faling

what is the dc charging current (maxm)?
what is your current fuse rating ?

based on that first have the fuse as advised by 'IanP'.

does the battery charger is used for charging the same batteries or
is it used as general purpose for charging different batteries ?

when does the fuse blowsoff?

give the load and other setup.

srizbf
25thmay2010

 

[chanchal.chauhan]

Re: Fuse Faling

Battery charging current is 7Amps & fuse rating is 15Amps.
It is using for charging the different battery @ 7Amps max. current.

H/w is already designed & working fine previously with all the fuse rating.

Fuses is blows off while charging the battery in CC mode & 7Amps current is drawing by the battery.

But when we tested for charging it works fine for 10 days. On 11th day Fuse blow off.

Any help is greatly appreciative.

Regards
Chanchal

Added after 1 hours 41 minutes:



How to control or suppress surge current?

Regards
Chanchal Chauhan

 

[srizbf]

Re: Fuse Faling

the problems you have mentioned requires careful observation and immense patience.

since on 11th day the fuse blows off,
the exact cause of the problems cannot be seen easily.

there can be only can be ... etc.

if ther is a circuit then it can reduce the time somewhat.

so , there are many many cause that may make fuse off.

since it is dc converter ,
one may be the changing value of component parameters
due to temperature.

and the temp. is increasing slowly in your case.
so be patient and observe the problem.

check electrolytic cap in the o/p side first .
is it correct rating and from good manufacturer.
what about its temp on 10th day?

so check one by one and find the cause.
with regards,
srizbf
29thmay2010