After fixing two power fuses blown

[Multi-Tech.]

After fixing two power fuses blown in electric Transformer one of the two fuses got blown immediately on no load. What could cause it and could the effect be on the Transformer.

 

[waross]

It happens.
Why did the fuses blow in the first place?
Often the current that blows two fuses will compromise the third fuse.
We used to see this a lot with fuse protected motors.
Good practice was to replace all three fuses when two motor fuses blew.
Transformer inrush may be 3 to 4 time as great as motor starting inrush.
Did you replace the fuses with the same type of fuse?


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[RRaghunath]

Fuses on transformer primary are very reliable and fast acting protection.
Thus, any fuse blowing must be taken seriously and investigated thoroughly. Any casual attitude towards protection system could cost lives.

 

[waross]

What size transformer? What voltage?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[thermionic1]

Was the transformer tested (Megger, TTR, etc), prior to replacing the fuses? If a fuse blew the second time that is a good indication of trouble. If the fuses are on the HV side of the transformer, that could indicate a fault in the transformer itself.

Depending on the size of the transformer, this could be a repair, or it could be a replace situation.

 

[waross]

At 480 Volts and at 600 Volts it is common for the third fuse to be compromised when two fuses blow.

Bill
--------------------
"Why not the best?"
Jimmy Carter