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thanks ghurd
By electrondady1, Section Controls Posted on Wed Jun 4th, 2008 at 05:08:15 PM MST
more resistance=less mechanical load on vawt alternator

a simple bit of rudimentary electrical knowledge has changed my insight .
in regards to loading the mill,
in the case of a vawt with five heaters in line,
initially one would want all five in series to create a large resistance
(minimal currant passage )
allowing the mill to start.
as rpm /voltage increases it would be ideal to have the individual heaters drop out of series
and be added in parallel.
(maximum currant)
so what would be the effect on the heaters having two parallel circuits with a different resistance on each.
the line with the greatest resistance would run cooler
this could be problematic
as an alternative
a properly sized resistance heater(allowing the mill to start)
is joined by additional circuits of the same resistance
as the mill gains speed.
am i on track here?

thanks ghurd | 13 comments (13 topical, 0 editorial)

Re: thanks ghurd (3.00 / 0) (#1)
by ghurd on Wed Jun 4th, 2008 at 01:30:55 PM MST
(User Info)

The series parallel thing. I think that's a mistake if you mean the heaters are the same, but I don't know.

IE: it would only be 4 steps.
If each heater is 10 ohms, the resistance would go 50, 8, 4.3, 2.86, then 2 ohms.
Pretty large jumps?
The 6 heaters and 2 each of star and delta thing would have the steps a bit more reasonable?

Switching 6 heaters between 4 configurations isn't a problem. Just a few relays and a logic circuit.

Probably need a cut-off circuit so there is no load until at least 6MPH, and (if it was me) more like 8MPH.

The switching speed (RPM?) would need some play. Unloaded at 6MPH may be faster than loaded at 6MPH. If you know what I mean. Sorry if thats mostly pertenint to HAWTs, but my VAWTs never work much.

If the PMA had 12 wires out, then it would allow 4 voltages.
If one "coil" made 10V, the choices would be 10V, 17V, 20V, and 34V.
The available power would be the same, but the available power, voltage and resistance could be tweaked to match.

Might even be helpful if sometimes the sine wave was only half wave rectified.
That would bring the effective voltage coult up to 8.
For 30 combinations. Yea, I think it's 30 instead of 32. Didn't think it through. Kind of in a rush right now.

The PWM Stamp or Picaxe thing could fix some of the issues. Gizmo Glenn's site might have something related.
Seems like "low frequency", 500Hz to 5KHz?, could fix most of the issues, if someone (not me) understood those chips. And wind and TSR and loads and power available and PMA efficiency.

Myself?
I'll be happy with the 12V 10W my kind of fly-able thing dumps,
Smile,
Pay my gas bill,
And be happy the insulation is good.

With luck, someone posted something better that this while I was 1 fingered typing.
G-

Re: thanks ghurd (3.00 / 0) (#2)
by electrondady1 on Wed Jun 4th, 2008 at 02:52:19 PM MST
(User Info)

yikes!!
,sorry i asked.
thats mostly over my head.
obviously ,i will need another method.

[ Parent ]

Re: thanks ghurd (3.00 / 0) (#3)
by electrondady1 on Thu Jun 5th, 2008 at 07:21:04 AM MST
(User Info)

i wonder if it would be simpler and within my understanding
to have a heater hardwired to the mill
and then use some sort of thermostat on the first heater
to close a ciruit on a second heater.

the thermostat would need to work in reverse so to speak
closing a switch when a predetermined temperature is reached,

when the second heater reaches it operating temperature another unit
could be switched in.

[ Parent ]

Re: thanks ghurd (3.00 / 0) (#4)
by ghurd on Thu Jun 5th, 2008 at 09:10:01 AM MST
(User Info)

Too slow reacting.

Ain't this fun?

[ Parent ]

Re: thanks ghurd (3.00 / 0) (#6)
by vawtman (vawtman(at)charter(dot)net) on Thu Jun 5th, 2008 at 05:49:41 PM MST
(User Info)

Hi Edaddy,
Why not have one element matched to the predicted full load of the turbine?

The resistance of the element is there but would gradually increase until it's rating.

I don't think starting would be an issue.

Am i wrong here?

[ Parent ]

Re: thanks ghurd (3.00 / 0) (#7)
by ghurd on Fri Jun 6th, 2008 at 12:04:24 PM MST
(User Info)

Very wrong.

Say it is a 12V 1000W machine.
Full load is 14.5V and 69A. That needs a resistance of only 0.21 ohms. Close enough to a dead short to act like a shorted windmill, in my experience with small stuff.

Direct windill heating seems to be a nightmare.

Zubbly did it with giant caps, and documented it. I think someone else (or 2) did too, but I can't recall who.

Maybe Hugh's Nirvana did heating(?), but it had circuits that were RPM and Hz driven, IIRC.

MtnMike must have low TSR blades?
I can't see it working well with high speed lift blades. Might be OK for a water pumper... OR a VAWT!

I am not an expert... I simply stated something about parallel resistance.
A 'smack in the face with the obvious facts' often causes the clarity needed to see deeper into the 'big' problem.
Sometimes my face hurts for weeks on end due to repeated smacking. :-)
G-

[ Parent ]

Re: thanks ghurd (3.00 / 0) (#8)
by vawtman (vawtman(at)charter(dot)net) on Fri Jun 6th, 2008 at 03:39:09 PM MST
(User Info)

Hi Ghurd
Back in the 5hp cogging conversion days.I had a 2100w hand dryer element hooked up between 2 of the 3phases and there was no difference at startup with the element there or not.It got pretty warm but maybe half it's rating.

Maybe because it took a stiff breeze to break cog.

That setup and gearing went to my pile after one afternoon. :v)

Mark

[ Parent ]

Re: thanks ghurd (3.00 / 0) (#9)
by elvin1949 (elvin1949@yahoo.com) on Sat Jun 7th, 2008 at 12:40:13 AM MST
(User Info)

G
DaveB did it direct hookup. But i think he used High Volts.
later
Elvin

[ Parent ]

Re: thanks ghurd (3.00 / 0) (#5)
by MtnMike on Thu Jun 5th, 2008 at 10:11:07 AM MST
(User Info)

I currently use three 20 ohm heaters and two relays to acheive 3 different loads.
To start I have two wired in series for 40 ohms, as the wind increases I cut out one of the heaters by bypassing it with a relay to then have 20 ohms. As the wind increases further, I cut in a third load in parrallel with the 20 ohm load for 10 ohms.
This works quite well with my setup. It runs up to about 65Vdc which is pretty much all the power I can get out of the mill.
The heaters are oversized to begin with, they are 660W at 110V bulb base heaters, so I never have to worry about overloading them.
You could use this concept with more heaters and relays to acheive the desired loading.
You should use equally sized resistances when running them in parrallel, otherwise the lowest resistance wil get more power, so you would then need to size the heaters based on the power each of them will see. If they are all oversized and can handle your max power at the rated voltage, then it doesn't realy matter how you hook them up.

Re: thanks ghurd (3.00 / 0) (#10)
by john j on Mon Jun 23rd, 2008 at 06:27:24 AM MST
(User Info)

Comments please: picture a scooter, small 50cc or something. The generator, pm, in this machine is hooked directly to the switch on the handlebars. If you try to jump start this, it will make the headlight glow, engine turning as you push it, doing, say 3 mph. And the lights go brighter and brighter as engine rpm rise.
Imagine taking this generator, (complete, with the bulbs now placed in my living room)and placing it on my vawt. Any reason why this wont work? No relays or anything.
Thanks.
Cheers, john j

Re: thanks ghurd (3.00 / 0) (#11)
by ghurd on Mon Jun 23rd, 2008 at 09:44:12 AM MST
(User Info)

Might post you own story about it.
I expect it won't work very well. Needs high RPMs, very low output.
Google Search the Board for magneto.
It will need a battery.
G-

[ Parent ]

Re: thanks ghurd (3.00 / 0) (#12)
by TomW on Mon Jun 23rd, 2008 at 10:45:51 AM MST
(User Info)

John;

It is considered rude and unfriendly to divert a thread to your own unrelated question.

Please bear that in mind before posting.

Just for your information.

Tom

"Education consists mainly of what we have unlearned."--Mark Twain
[ Parent ]

Re: thanks ghurd (3.00 / 0) (#13)
by john j on Wed Jun 25th, 2008 at 03:10:30 AM MST
(User Info)

Sorry for that. I figured it was on topic.
Cheers, john j

thanks ghurd | 13 comments (13 topical, 0 editorial)

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