Transformer input fuse holder 1

[Fernando79]

Guys ,
I am working in a plant , we have a Transformer 3~ 45KVA
480 to 380 V , the input fuses always Very hot and from times to times it burnt out , the current is 52 Amps which is normal , Do u know why ?? anyone has the same problem to help ??

Thanks
Fernando

 

[wbd]

What is the fuse size? What kind of load is being fed? Is there alot of harmonic component of the current?

 

[Fernando79]

The input Fuses are 60 Amps and the output of the Transformer is fed to DC motor field converter ?
I am not sure if we have Harmonics in the input , but the Temp is always high in the fuses holder.
any feed back ??

F

 

[waross]

Using 60 amp fuses for a 52 amp load is marginal. Make sure that the fuse holders are a close fit with the fuses. They must be tight and they must be the same shape as the fuse ends. If fuse holders for round fuses are bent out of round, the fuses will overheat. Poor quality fuse holders with weak spring tension will overheat.
Your fuse may be protecting the transformer from occasional overloads.
Some fuses naturally run hot and sometimes fuses are supposed to blow.
If you are not using dual element fuses consider changing to dual elements.
respectfully

 

[waross]

If you suspect that poor quality fuse holders are an issue consider using Bussman TRON Clip-Clamps.

http://www.connex-electronics.com/?url=/html/products/bussmann/buss_accessories_main.html

respectfully

 

[Electic]

I don't know if your DC motor converter imposes a harmonic draw on your system, but if your ammeter reads only RMS as though a nice sine wave, the actual current draw may be higher.

As Waross says, 60A fuse on 52A load is marginal, and the load might actually be higher?

 

[Fernando79]

This problem happened more than 4 times and also the same fuse holder has been changed every time we have this problem ?? Guys do u think we should put Circuit breaker instead ??? what is the backward of that ???
and in my case , the fuses are from the same manufacturer and the fuse holder is tight where the wire is .
I was thinking maybe the cable is not that good and we should try the cable ?? what do u think guys ??
I dont know how much the cable cross section maybe 25 mm FLEX.

Thanks for help

 

[luis7006]

Hello,

I also recommended you before to make any change of the fuses, firstly monitoring the rms current through this circuit (trx input)and in that way be sure about the total current.

You may have some high harmonics content that combined with high loading may cause low voltage and then, higher currents and from time to time burnt fuses.

Of course, looking for the whole picture is always important: fuse qualiy, load, fuse holder and so on.

Best Regards