running 3 phase motors on RE

 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

  On Sat, 24 Jul 2004 01:17:56 -0700, "gene lewis"


What is an RE system?


Regards,

John Phillips

 John Phillips wrote:

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

 On Sat, 24 Jul 2004 14:20:30 -0700, "gene lewis"



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