Question:
greetings all, I wondered if producing 3 phase (240 or 480V) power with a RE system is feasible or even possible. I would have to run at most a 7.5 HP motor. this is not for a current use, just ideas for the future. (when I buy a house I’ll be building a small machine shop, and will need to "lectric it up") Is a motor that big just too much for a sensibly sized RE system, by which I mean most likely grid tied PV, not hydro, small enough to install on a single family home in the city. (Portland, OR)? I know there are tons of variables, I just hope for a fairly simple "yeah you can do that for not too much $", or "yeah, but it’ll be real expensive" or even "nope, cant do that, not ever, not no how"
Thanks, gene
Response:
>greetings all, >I wondered if producing 3 phase (240 or 480V) power with a RE system is >feasible or even possible. I would have to run at most a 7.5 HP motor.
gene, What is an RE system? Regards, John Phillips
Response:
>>I wondered if producing 3 phase (240 or 480V) power with a RE system is >feasible or even possible. I would have to run at most a 7.5 HP motor. > What is an RE system?
RE = Renewable Energy. The three main limits to an RE system are 1) maximum instantaneous power required, 2) maximum kilowatt-hours required per day (week,year,etc), 3) financial resources. The first two are certainly available but not exactly cheap. The last is strictly up to you. I believe most folks who run shops out in the woods wind up using a diesel generator when they want to work the big tools and the wind, pv, hydro is reserved for everything else. If you use biodiesel you can at least give a nod to making it renewable. Anthony
Response:
– Hide quoted text — Show quoted text ->>I wondered if producing 3 phase (240 or 480V) power with a RE system is >>feasible or even possible. I would have to run at most a 7.5 HP motor. > What is an RE system? > RE = Renewable Energy. > The three main limits to an RE system are 1) maximum instantaneous power > required, 2) maximum kilowatt-hours required per day (week,year,etc), > 3) financial resources. > The first two are certainly available but not exactly cheap. The last > is strictly up to you. I believe most folks who run shops out in the > woods wind up using a diesel generator when they want to work the big > tools and the wind, pv, hydro is reserved for everything else. If you > use biodiesel you can at least give a nod to making it renewable. > Anthony
Thanks. I guess the question really is whether the inverters on the market are able to produce 3 phase, or, if not, if a phase converter is a type of load that would give an inverter fits. I know that those big motors draw a lot of current on start up, hence the 240 or 480V. The time the motor would actually be running is probably less than 2 or 3 hours/day, but it will be started and stopped probably 100-300 times in 6-8 hours. I assume the easiest way to provide such large peak surge currents would be to use a grid tied system, and just hope to offset my usage with it; but it costs a ton to have 3 phase brought in by the utility, so I hoped an inverter would be able to produce the 3ph without using a converter (which is just a motor connected to a generator, pretty inefficient.) Are big motors like electric heating, in that theyre something that’s just not practical in an RE situation? Gene
Response:
– Hide quoted text — Show quoted text – >greetings all, >I wondered if producing 3 phase (240 or 480V) power with a RE system is >feasible or even possible. I would have to run at most a 7.5 HP motor. >this is not for a current use, just ideas for the future. (when I buy a >house I’ll be building a small machine shop, and will need to "lectric it >up") >Is a motor that big just too much for a sensibly sized RE system, by which I >mean most likely grid tied PV, not hydro, small enough to install on a >single family home in the city. (Portland, OR)? >I know there are tons of variables, I just hope for a fairly simple "yeah >you can do that for not too much $", or "yeah, but it’ll be real expensive" >or even "nope, cant do that, not ever, not no how"
>Thanks, >gene
Do a google search of the rec.crafts.metalworking group for "variable frequency drive" or VFD. These units can take in single phase, and output three phase. (input and output voltage will be the same) VFDs are used all the time in home shops to run three phase motors. A 7.5 hp unit would probably cost about $600. Here’s a supplier I often see recommended http://web2.automationdirect.com/adc/Shopping/Catalog/AC_Drives_-z-_M… A transformer might also be required. One of the advantages of using a VFD is that you can program it for slow start, lessening the startup surge. My guess is that a VFD would run off a pair of large Xantrex SWs. You’d want to get that answer directly from Xantrex though http://www.xantrex.com/index.asp They might even have a better solution. The question must have come up before. FWIW, we run all our normal loads (some big ones), *and* the startup surge of a 4hp air compressor, at the same time at our off-grid place. If you need a guinea pig to find out about adding 3 phase shop motors, just ship me a 2 hp VFD… I’ll change out my table saw motor, test the combination, and send you a nice report.
Wayne
Response:
– Hide quoted text — Show quoted text -> The three main limits to an RE system are 1) maximum instantaneous power > required, 2) maximum kilowatt-hours required per day (week,year,etc), > 3) financial resources. > The first two are certainly available but not exactly cheap. The last > is strictly up to you. I believe most folks who run shops out in the > woods wind up using a diesel generator when they want to work the big > tools and the wind, pv, hydro is reserved for everything else. If you > use biodiesel you can at least give a nod to making it renewable. > Anthony >Thanks. I guess the question really is whether the inverters on the market >are able to produce 3 phase, or, if not, if a phase converter is a type of >load that would give an inverter fits. >I know that those big motors draw a lot of current on start up, hence the >240 or 480V. >The time the motor would actually be running is probably less than 2 or 3 >hours/day, but it will be started and stopped probably 100-300 times in 6-8 >hours. >I assume the easiest way to provide such large peak surge currents would be >to use a grid tied system, and just hope to offset my usage with it; but it >costs a ton to have 3 phase brought in by the utility, so I hoped an >inverter would be able to produce the 3ph without using a converter (which >is just a motor connected to a generator, pretty inefficient.) >Are big motors like electric heating, in that theyre something that’s just >not practical in an RE situation?
Probably the most economical solution is to replace the three phase motor with a single phase motor. From an efficiency standpoint, the use of an mg set would be better than using a three phase inverter in a grid tied situation. The mg set would be a 240 volt single phase motor driving a 480 volt three phase generator. The starting currents on motors approach 10 times full load current. Regards, John Phillips
Response:
– Hide quoted text — Show quoted text ->greetings all, >I wondered if producing 3 phase (240 or 480V) power with a RE system is >feasible or even possible. I would have to run at most a 7.5 HP motor. >this is not for a current use, just ideas for the future. (when I buy a >house I’ll be building a small machine shop, and will need to "lectric it >up") >Is a motor that big just too much for a sensibly sized RE system, by which I >mean most likely grid tied PV, not hydro, small enough to install on a >single family home in the city. (Portland, OR)? >I know there are tons of variables, I just hope for a fairly simple "yeah >you can do that for not too much $", or "yeah, but it’ll be real expensive" >or even "nope, cant do that, not ever, not no how"
>Thanks, >gene > Do a google search of the rec.crafts.metalworking group for "variable > frequency drive" or VFD. These units can take in single phase, and > output three phase. (input and output voltage will be the same) VFDs > are used all the time in home shops to run three phase motors. A 7.5 > hp unit would probably cost about $600. Here’s a supplier I often see > recommended > http://web2.automationdirect.com/adc/Shopping/Catalog/AC_Drives_-z-_M… > A transformer might also be required. One of the advantages of using a > VFD is that you can program it for slow start, lessening the startup > surge. > My guess is that a VFD would run off a pair of large Xantrex SWs. > You’d want to get that answer directly from Xantrex though > http://www.xantrex.com/index.asp They might even have a better > solution. The question must have come up before. > FWIW, we run all our normal loads (some big ones), *and* the startup > surge of a 4hp air compressor, at the same time at our off-grid place. > If you need a guinea pig to find out about adding 3 phase shop motors, > just ship me a 2 hp VFD… I’ll change out my table saw motor, test > the combination, and send you a nice report.
> Wayne
Wayne, I’ve seen you over at R.C.M., right? Thanks for the info. It’s relieving to hear that someone *is* running big motors off grid already. The VFD is in the mail, you should have it on monday.
Gene
Response:
Talk to Rainbow Power Company in Australia. They sell 3 phase back to the grid. – Hide quoted text — Show quoted text -> greetings all, > I wondered if producing 3 phase (240 or 480V) power with a RE system is > feasible or even possible. I would have to run at most a 7.5 HP motor. > this is not for a current use, just ideas for the future. (when I buy a > house I’ll be building a small machine shop, and will need to "lectric it > up") > Is a motor that big just too much for a sensibly sized RE system, by which I > mean most likely grid tied PV, not hydro, small enough to install on a > single family home in the city. (Portland, OR)? > I know there are tons of variables, I just hope for a fairly simple "yeah > you can do that for not too much $", or "yeah, but it’ll be real expensive" > or even "nope, cant do that, not ever, not no how"
> Thanks, > gene
Response:
>I wondered if producing 3 phase (240 or 480V) power with a RE system is >feasible or even possible. I would have to run at most a 7.5 HP motor.
IIRC you can hook up 3 (or 6, or 9) Outback inverters and get 3 phase. But the VFD is probably easier and gives you speed control, too. — Cats, Coffee, Chocolate…vices to live by
Response:
>Wayne, >I’ve seen you over at R.C.M., right?
Yup. >Thanks for the info. It’s relieving to hear that someone *is* running big >motors off grid already.
Big loads (within reason) aren’t difficult, especially if they’re only on for short periods. It’s all the little sneaky ones, like the idle load of big inverters that you have to watch out for. >The VFD is in the mail, you should have it on monday.
When we first moved off-grid, we rented an extra large PO box to handle all the tool catalogues. Suppliers have cut back on paper in favor of Internet though, so that big box has been wasted the last few years…. until now. ;-) Wayne
Response:
You might try a CEDARBURG Rotary converter. It passes the 240v legs through to the motor and creates the third leg. I just installed a 3HP model at work and it runs great. The unit is fused with 15A fuses. This one has a spinning armature coil but they have smaller ones with just stationary coils & caps. 3HP model costs about $700
– Hide quoted text — Show quoted text -> greetings all, > I wondered if producing 3 phase (240 or 480V) power with a RE system is > feasible or even possible. I would have to run at most a 7.5 HP motor. > this is not for a current use, just ideas for the future. (when I buy a > house I’ll be building a small machine shop, and will need to "lectric it > up") > Is a motor that big just too much for a sensibly sized RE system, by which I > mean most likely grid tied PV, not hydro, small enough to install on a > single family home in the city. (Portland, OR)? > I know there are tons of variables, I just hope for a fairly simple "yeah > you can do that for not too much $", or "yeah, but it’ll be real expensive" > or even "nope, cant do that, not ever, not no how"
> Thanks, > gene
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Response:
Your best bet is to get a diesel generator for running such a large electrical load. No RE system I am aware of is even remotely economical in comparison. Nor is it as reliable (what do you do on a cloudy day when you want to run your machine?).
– Hide quoted text — Show quoted text -> greetings all, > I wondered if producing 3 phase (240 or 480V) power with a RE system is > feasible or even possible. I would have to run at most a 7.5 HP motor. > this is not for a current use, just ideas for the future. (when I buy a > house I’ll be building a small machine shop, and will need to "lectric it > up") > Is a motor that big just too much for a sensibly sized RE system, by which I > mean most likely grid tied PV, not hydro, small enough to install on a > single family home in the city. (Portland, OR)? > I know there are tons of variables, I just hope for a fairly simple "yeah > you can do that for not too much $", or "yeah, but it’ll be real expensive" > or even "nope, cant do that, not ever, not no how"
> Thanks, > gene
Response: