R448AVR in Place of R449AVR?

A side by side comparison of the instruction manuals shows that the 448 has more options then the 449, but only a call to the manufacturer can give a definitive answer if it is a drop-in replacement.

As an outsider, I have but one question.

Is the reward worth the risk?

What happens, what do you have to lose, if you try it and it doesn't work?

Yes it is!

Looked at manuals flagged by RAMConsult, I see that the bench test instructions require

1. a 100-140V supply to X1-X2 for R448 - rated 10amp for 10s
2. 240V to X1-X2 for R449 - rated 15 amp/10s

This suggests R449 is used with generators having higher field and AVR power voltage.

Unfortunately, using only 120 V on R449 it is unlikely to work.

The board dimensions/fixings and controls look same but R449 has no onboard fuse - diagrams show external fuse.

There are 3 different schemes in manual, or more, for powering AVR from generator - which do you have?

If I was desperate for power and it was one of the non-PMG schemes, I might try putting 120V secondary of 240/120 tool transfo in series with AVR power winding to get more volts for R449. It's more peak volts on field winding but the AVR will limit field current.

Experimentation needed to get best 240V primary phase and polarity to get more volts to AVR.

Or 240/240 transfo to feed X1-X2 of R449 from generator main winding (in place of PMG/whatever) - poor response to sudden heavy loads but maybe you do not have such loads.

Hi, and thank you for your effort.

The alternator in question is fitted with a brand new PMG that supplies up to a max. of 180VAC to inputs X1, X2 & Z2 of the R449 AVR.

So, upon startup, the initial input voltage should work on the R448 too. I mean, surely if the input voltage is too high then the fuse will blow right?

Also, upon startup, the initial output voltage of the main field will be low since pot P2 (output voltage and no load) will be set to full anti-clockwise so this will not be too much of a worry.

Sorry, I got my wires crossed on which was gen fitting & available spare.

180V is 50% more than what is probably 120VAC nominal for R448. There is risk the big black electrolytic capacitor will blow. There is probably a big volt rating margin to cover over -excitation /load reject. 180V x root 2 = 255V, maybe 300V rating with 50% voltage surge for 30s. I would be worried about power transistors, too much voltage they will just short and give over excitation & overvolts to all your loads. Less margin over spec sheet maximum than caps. Electro-mech loads could survive but electronics go pop.

If possible , transform PMG volts to 120 (three single phase transfo). There is a good margin on field volts on resistive loads & if you do not have big loads to start-up requiring field forcing.

Thanks. I have managed to get into email contact with their support dept and are awaiting a response. Email has been confirmed.

Just a wild thought. The PMG might be Y connected and a D connect possible with less volts.

I am currently communicating with Leroy Somer in the US and will post a short note here if the issue was resolved.

This was resolved thank you.

The R448 can indeed be used in place of the R449, however the R448 was designed for lower rated alternators. As our generators are gas powered we limit the outputs of the alternators with Woodwards, thus we can safely use the R448 since we are not drawing higher than 350KW per alternator, which puts them safely into a lower range.