Caterpillar VR3 - SE AVR fuses are blowing

[themes1]

Dear friends i am new guy for this forum and right now im repairing 2 catepiller generators which are having VR3 - SE AVR Unit. both units having 2 fuses fixed outside and both fuses are blowing when the generator starts at once.

if anyone having experience about this problem pls let me know what is the problem and how to solve it. new AVR is very expencive and if anyone having circuit diagrem of this AVR pls send it to me to repair it by myself.

Thank you

hemantha soysa

 

[IBRCAN]

Some clarification is needed. You say "both fuses are blowing when the generator starts at once". Do you mean to say both fuses on both units are blowing? Exactly when are these fuses failing? Are these generators being paralleled? Have these units been in operation for some time or are have they just been installed?

The fuses are installed in 2 of the 3 voltage sensing leads (assuming 3 phase sensing). A short to ground in the exciter field (connected to F1 & F2) could cause these fuses to open. Failure of the regulator itself is also quite possible. In that case, you would need to upgrade to a VR6 AVR, as the VR3 is obsolete.

Service manual is SENR3904, which can be purchased from local Cat dealer.

 

[themes1]

Dear Mr. IBRCAN 2 generators are using separately and as u said these fuses are using the sensing leads. im and electronic technician too and myself i checked the avr today and i found out one transister and 3 phase bridge rectifier not working properly. i will buy it tomorrow and tell u if im success.

thanks for ur valuable information