rotrax
Well-Known Member
Hi- did you mean that? Surely a DC alternator is a contradiction in terms. As the name implies an alternator produces alternating current.
Now this is only a thought. 230vAC from 30HPengine
- Thread starter stuhaynes
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Hi- did you mean that? Surely a DC alternator is a contradiction in terms. As the name implies an alternator produces alternating current.
William_H
Well-Known Member
Whats in a name?
I think the "DC Alternator" name as a description is as good as it gets for what has become almost universal for DC power generation and battery charging. It is in fact a 3 phase AC alternator (about 300 to 1000 hertz depending on engine speed) with integral diodes to produce DC. Early in its introduction it was known as an alternator to distinguish between it and the older generator. Which just to be confusing is an alternator with rectification of the AC by switching achieved at the commutator to make DC but never called an alternator.
We now have run out of correct description for the 50 hertz generating alternator except a lot of people on this forum call them a generator when they are stand alone with engine. language is an uncertain science.
olewill
I think the "DC Alternator" name as a description is as good as it gets for what has become almost universal for DC power generation and battery charging. It is in fact a 3 phase AC alternator (about 300 to 1000 hertz depending on engine speed) with integral diodes to produce DC. Early in its introduction it was known as an alternator to distinguish between it and the older generator. Which just to be confusing is an alternator with rectification of the AC by switching achieved at the commutator to make DC but never called an alternator.
We now have run out of correct description for the 50 hertz generating alternator except a lot of people on this forum call them a generator when they are stand alone with engine. language is an uncertain science.
olewill
TrueBlue
Well-Known Member
Quite apart from anything else, I think you'd find the MarineMart alternator is a big beast and you'd have huge trouble mounting it (hence the comment about brackets). Not only that, but methinks the bearings may not be suitable for any sideways thrust. They are designed to be driven in line.
It's one thing to have an governed to a specific speed - Beta used to do a unit called a PropGen, but it has disappeared - and quite another when you want to set a normal multispeed engine to a specific speed. The latter has a governor.
Your easiest solution is to fit an alternator nearest to your power requirement and let the battery capacity take the excess load of the washing machine via an inverter. After all the load is not continuous.
It's one thing to have an governed to a specific speed - Beta used to do a unit called a PropGen, but it has disappeared - and quite another when you want to set a normal multispeed engine to a specific speed. The latter has a governor.
Your easiest solution is to fit an alternator nearest to your power requirement and let the battery capacity take the excess load of the washing machine via an inverter. After all the load is not continuous.
greenalien
Well-Known Member
One more thought - if you really need to run a washing machine, why not just buy a cheap generator to run it - there are plenty of 3kW devices available for a couple of hundred pounds, such as http://www.ebay.co.uk/itm/BRAND-NEW-3kw-3-8-kva-PETROL-GENERATOR-12-110-240-Volt-/360423402007 - and if you've got room for a washing machine, I'm sure you could squeeze a genny in somewhere!
stuhaynes
Well-Known Member
Mmmm. Not true. as Live aboards with 30 X 9'6 Kathe chucks out even socks if they're not used for a fortnight! We've gone from a 5 berth to a 3 berth to get the 'stuff' in.
I have a question though... Would it be better, cost wise, to install a DC generator with inverter? The ac generator is impractical because, when cruising we would be unable to maintain the RPM to provide 50Hz. Over 50HZ, we could fry the computers. Under 50Hz, I just don't know.So...??
Added. We have a 1KW Yamaha genny, the suitcase jobby. (it lives under the stern deck)The only 3.5's I've seen are the frame tents of the camping world. We would have to lose something to have one of these. I was thinking more in line of something I could stick in the engine space (which is not even big enough to contain the engine), well it is but only just
greenalien
Well-Known Member
OK, one more option - a low-power washing machime such as http://www.thecanalshopwhilton.co.uk/html/washing_machines.html
Because these don't have heaters, they don't need 3kW - but still do the manual hard work for you - and they don't take up as much space as a 'conventional' machine. Since modern detergents don't need high temperatures to work effectively, a boiled kettle should be enough hot water for a wash, and they should run OK from your small genny, although you'd need to check that detail.
Because these don't have heaters, they don't need 3kW - but still do the manual hard work for you - and they don't take up as much space as a 'conventional' machine. Since modern detergents don't need high temperatures to work effectively, a boiled kettle should be enough hot water for a wash, and they should run OK from your small genny, although you'd need to check that detail.
William_H
Well-Known Member
Washing machines
Interesting ... Here in Oz I have never seen a domestic washing machine with a heater in it. You connect up the hot and cold water supply and if you choose a hot wash it opens a valve to the hot water supply.
However I have never seen ours used with hot wash in 30 years. We just use cold water. seems OK.
I can understand if ambient temp is really low a bit of hot water from a kettle would help.
I imagine the washers in the link to be good for a boat. A twin tub means you can use the same washing water for several loads but saving water on rinse is not so easy. I would think a spin drier is essential.
good luck olewill
Interesting ... Here in Oz I have never seen a domestic washing machine with a heater in it. You connect up the hot and cold water supply and if you choose a hot wash it opens a valve to the hot water supply.
However I have never seen ours used with hot wash in 30 years. We just use cold water. seems OK.
I can understand if ambient temp is really low a bit of hot water from a kettle would help.
I imagine the washers in the link to be good for a boat. A twin tub means you can use the same washing water for several loads but saving water on rinse is not so easy. I would think a spin drier is essential.
good luck olewill
stuhaynes
Well-Known Member
It was having a twin tub that shamed me into getting an auto washer, much more civilised.
Since I last posted on this thread I've had a look at the washer, and it does have a cold wash facility. I imagine (but I'm not entirely sure) that the 1500 watt inverter should cope with the 'mechanics' of turning the machine, particularly when under way. Only thing is, our inverter is a modified sine wave and I'm sure I've read somewhere that things like auto washers don't like the taste of this kind of lecky. If it is true then the whole idea is a no-no. 
Dockhead
Well-Known Member
A good question, but the description is accurate. The native current is AC - but unusable in that state, because the frequency varies with RPM. This rough AC current is rectified to produce a nice DC current. Describes all car alternators since at least 1970.
This is the most efficient and reliable way to produce elec power with your main engine. If you need AC power, just invert it. All simple, proven, reliable, relatively inexpensive technologies. No need to go wacko experimental devices. Do you want to be the alpha tester?