Carver Owners Forum

So I was on Cummins Quickserve portal tonight downloading the manual for my Onan generator. As I was looking closer at the nameplate data (see pic) I realized it says it is a 3000rpm / 50Hz. The 50Hz is kinda throwing me for a loop. If you look close, to the right of the "Model No" it looks like a sticker has been applied with "10.0MDKWB" on it. It kinda looks like it is peeling up a bit at the end so I don't know what that's all about either.

I used the actual Serial Number from the nameplate on the Cummins Quickserve portal to find the manuals and it says the "Ship Date" was March 31, 2000 so I feel like this is the original generator, but cannot figure out why they'd put a 50Hz generator in a boat designed for the US with all other pumps/motors/systems/etc. onboard the boat rated at 60Hz.

In addition, the nameplate data indicates the kilowatt rating as 8.0, but the leading numbers of the model number seems to indicate it is a 10.0kW generator, which is what was advertised when we were initially looking at this boat.

Has anyone seen/heard of anything like this? Every time a turn around I run into another mystery! Thanks in advance!!

Well, after a LOT of searching, I might have found my answer - but if anyone has anything to add I would certainly appreciate it!

I found a spec sheet from Cummins with the attached details. From what I can deduce, my guess is that the gen set was produced as an 8kW 50Hz model, but was "switched" to the 10kW 60Hz model, hence the sticker that was applied over the standard nameplate model number. I'm not sure why they didn't have stickers to alter the 3000rpm and the 50Hz portions of the nameplate - that would have certainly made things a little clearer. Oh well, that's my best guess but I am open to feedback. And hopefully this might help someone else out there who runs across something like this.

Ya most generators I know are all designed to deliver 50 and 60Hz to accommodate different markets. Regardless of what the label says though, I always confirm the output with a frequency meter. Frequency output can be affected by some running conditions so it's really a critical piece of information to have any time the generator is running. For that reason, I really wish manufacturers would install these meters on the electrical panel. You can install one yourself though or simply a plug-in type for an outlet.

Good thread, thanks for sharing that with us.

The labelling on the genset is certainly confusing but the power differences at 50 and 60 Hz are not. That's pretty typical. I have a Westerbeke with a huge sticker on the side that lists all the specs at both 50 and 60 Hz (and it is also 8kW at 50Hz and 10kW at 60Hz)

Changing the frequency is just a matter of changing the speed it runs at. There is no electrical difference. The lower power output at 50Hz is due to the engine being only able to deliver a portion of the power at 3000RPM than it could at 3600RPM, or in the lower RPM group gensets 1500RPM vs 1800RPM. All of those are less than the engine is really capable of running at its rated RPM.

Same thing with any multi voltage motor. When used on 50 hz the motor hp gets downgraded by 20% as well as a 20% reduction in rpm. Bottom line, normal.

Thanks for the feedback!