hello and of course...help

[eclmech]

Hello all, I have been doing lot of reading on this site and I am truly impressed with the knowledge and info available. Good job every one.
Well i guess i just wanted to say hello and ask the library of knowledge available here a question.

I have a very, very old Weldanpower 150 that was riding around in the back of my service truck for the odd emergency on plow and construction equipment. Great little machine, surprisingly capable. Anyhow the Kohler 10 horse finally let go (some extra holes in crankcase) and I happen to have a 13 horse Honda sitting in the corner looking for a home. Well I mated the two and now I have a problem, the recifier for the exciter keeps burning out. I am aware that the flashing voltage of the Kohler was only 1.5-4 vdc but it was also available with a briggs or murphy at 12-14 volts. As far as I can see on Lincoln's website the internal parts were all the same. Any ideas??

thanks Keith

[Sandy]

Well I mated the two and now I have a problem, the recifier for the exciter keeps burning out. I am aware that the flashing voltage of the Kohler was only 1.5-4 vdc but it was also available with a briggs or murphy at 12-14 volts. As far as I can see on Lincoln's website the internal parts were all the same. Any ideas??

When you say the rectifier is burning out------do you mean one diode, or one of a pack??

I'm a long long ways from a gen set/welder guru, but here's my take on this. The only relationship between the engine and welder is that the engine turns the shaft at a particular rpm to achieve the desired results. The circuitry does the rest as long as the engine maintains the desired rpm under load.

When changing engines, as long as the torque curve and economy curve are similar, bolt it up, set the rpm and you are good to go (simplified version). A side note would be that the engine rpm is going to dictate every output of every component that runs off that shaft. That's how the coarse output of a generator gets adjusted, through engine rpm. The problem comes when a particular engine needs to run at a significantly higher or lower rpm than the original set up in order run in it's ideal torque curve and do the job.

If this is the case and there is insufficient adjustment, or no adjustment, then a pack that is 'tuned' for the new rpm range is going to be required.

I'm sure you have already covered all this, just rambling and maybe something will ring a bell. Thinking out loud, so to speak.

[eclmech]

Thanks Sandy. The rectifier used is a 34 A 800V bridge and it burns out only 1 of the diodes. Engine rpm are both 3650 unloaded. Also the resistance of the rotor is right on spec. I'm just a little stumped as the thing worked really well prior to me messing with it.

Keith

[Sandy]

The rectifier used is a 34 A 800V bridge and it burns out only 1 of the diodes. Engine rpm are both 3650 unloaded. Also the resistance of the rotor is right on spec. I'm just a little stumped as the thing worked really well prior to me messing with it.

I hate that. It's like the lights going out at the same time as a water line breaks. The mind wants to put them together as a common cause.. :)

Sorry I can't be of any help. It's almost like the trigger voltages aren't all exactly the same. Like one has a lower trigger voltage and is carrying all the current.

Sorry. Keep us up to date.

Hopefully some guru will come in here with the quick simple answer....

[mattc]

I have a portable (miller) 225 amp with a kohler engine on it, it has diferent rpm settings for weld and power, for weld the specs are 3000 rpm your engin sounds to be running about 20% higher rpm which might be effecting your welder (just a thought I dont know for sure)
also if you solder a MOV or metal oxide varistor I would say 100 or 125 volts and 20 joules rated, one across each diode it should protect the diode from the voltage spikes cause when you break your ark from welding If it explodes like a firecracker use a higher voltage. These things are cheap enough
another thought is your diode getting cooled good enough because over heating will kill them very fast

[TxRedneck]

glad mattc is back wih us :D

[mattc]

thanks, I never went too far just went under cover untill all the excitement blew over

[eclmech]

Thanks for the suggestion. I'l look into it. The engine rpms are right on spec according to the manual.

Keith