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Battery charger blowing fuses

RJT

Titanium
Joined
Aug 24, 2006
Location
greensboro,northcarolina
We have a used 220 3 phase charger for our electric lift truck, have had it about a year. We use the lift very occasionally and only need to charge it about once a month or 6 weeks. We turn the disconnect off to the charger when it's not in use to avoid the constant buzz it produces. When we turn the breaker on (charger not connected to the lift truck at this point) it blows a fuse about 1/3 the time. We had it checked by the manufacturer of the charging unit, they found nothing wrong and their advice " These are built to be left on and used every day, just leave it on". I hate the stupid buzz. Any other options?
 
Which fuse are you using can be the issue. You may want to look into different time delay fuses as that is what my customers use.

Sent from my SM-G960U using Tapatalk
 
I believe this is a 60 amp fuse, there are 3 of them (one for each leg), It doesn't blow the same fuse every time. Next higher amp fuse is a different configuration and won't fit. IMG_20211209_132559476.jpg
 
Looks like you won't be able to fit a tougher fuse in that holder then. Are you able to get a breaker or different fuse holder and transfer the wires over? I'm personally a big fan of breakers on equipment. So much nicer.

Or bypass the fuse holder entirely and let the upstream breaker do the work. If it's permanently wired in I don't see why that would be an issue. The existing fuses clearly aren't sized properly for inrush, and it doesn't make any sense to have a downstream breaker that will trip after the upstream breaker.

Safety people may disagree on principal of modifying safety systems but I personally don't care.
 
I don't remember the exact numbers, but in transformers in-rush current can be as much as 10 times their rating. There can also be residual magnetism in the core, and timing of energizing it will play a role in which of the phases may blow a fuse. Best remedy is to equip it with a soft start circuit, like was already suggested. The other thing to try is to energize the charger after the load is plugged-in - from experience (so anecdotally) in-rush seems greater when no load is connected on output.
 
Are the fuse holder clips clean and shiny?
Inrush current is momentary and should not blow fuses.

It is true that inrush current only lasts a few cycles in the waveform, but the question isn't only about time, but also about the amount of current. Consider the specification of LPJ-60SP the OP is using :

minimum 10 seconds at 500% rated current. So in other words his fuse is 60A, it will tolerate up to 300A for 10 seconds or so.

So then the question is what is that peak ? Take a look at page 26 here :

https://download.schneider-electric...File_Name=7400CT1901.pdf&p_Doc_Ref=7400CT1901

Bottom line, while the inrush current amount varies depending on the transformer design, on average it exceeds 10x rated current of the transformer. Thus it's unlikely that a 5x time delay fuse can reliably energize the charger in question.
 








 
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