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Steve,<\/p>\n
I had a question about the cruising alternators on the main engine. I have been reading Ken Williams’ blog and there was a significant amount of traffic on this subject. Bottom lime was concluding that they drew more power, hence fuel, then simply running there normal 20kw generator. They went on to suggest that Nordhavn as a company was no longer installing them on their boats. I know you area a big fan and I was wondering if you could shed some light on the subject<\/p>\n
thanks<\/p>\n
Scott<\/p><\/div>\n
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<\/p>\n
Howdy Scott:<\/p>\n
This is a complex subject and starts with the AC loads. If they are so high that you are forced into complex hydraulic drives for the engine driven alternator(s) there are going to be big efficiency penalties, and you may not be able to generate the required power in any event.<\/p>\n
Our approach works well for several reasons:<\/p>\n
In our case you have to consider the power losses of the inverters, the AC\/DC conversion at the alternator rectifier assembly, and poly-V belt drive losses. If our loads were continuous and high these conversion factors would make the genset slightly more efficient. But since the loads are only high on a periodic basis, we come out ahead on fuel.<\/p>\n
There is another factor to consider. If you are genset dependent, then you need a second unit, so you are 100% assured of reliable power. In our case, we have a choice of engines\/batteries\/inverter or genset, so with a single genset we are OK.<\/p>\n
And then we have the advantage of being able to sit for days at anchor without needing to charge the batteries or run the generator.<\/p><\/div>\n
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