# [EVDL] economy ac controller



## EVDL List (Jul 27, 2007)

from following the discussions here I have come up with and idea that may b=
e a bit crude and maybe not even possible but... for a motor large enough f=
or an automotive traction motor AC motors are cheaper (?) but their control=
lers are much more expensive(?) would it be possible to use a small DC moto=
r using a low power DC controller to drive a set of high amperage rotary co=
ntacts thats would switch the current back and forth providing a square AC =
waveform? will an AC motor run on a square waveform or must it be a sinwave=
? obviously this is not the most elegant or efficient way to do this but in=
my mind it should work pretty well...how far off base am I?

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## EVDL List (Jul 27, 2007)

Hmmmmm. Isn't this usually called a DC motor? only you are separating the
commutator from the rest of it in this case.

I am not sure that AC motors are cheaper than DC motors...seems like maybe
they should be because of not requiring the commutator, but in actual
experience, it doesn't necessarily seem so. Then again, alot of them are
liquid cooled, which is a bit better for sustained power output than an air
cooled design like the DC ones. And, I wouldn't necessarily agree that AC
controllers are more expensive either...it just happens that we can get by
with a controller with fewer features for many DC systems, but price out a
DC system with regen and such, compared to an AC system.... not sure
(because I'm doing just that, and even getting used components, I'll be
quite a bit more expensive than a new 9"ADC and Zilla1k)

Z




> robert harder <[email protected]> wrote:
> 
> >
> > from following the discussions here I have come up with and idea that may
> ...


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## EVDL List (Jul 27, 2007)

> robert harder wrote:
> > Would it be possible to use a small DC motor using a low power DC
> > controller to drive a set of high amperage rotary contacts that would
> > switch the current back and forth providing a square AC waveform?
> ...


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## EVDL List (Jul 27, 2007)

Actually, you arent that off base. I had the same
notion awhile ago and asked some old radar techs about
a design. I was told that it looked similar to an old
inverter design. It was a battery to slip ring to
commutator/brush to ac motor and back again. Keep in
mind that Cycle rate =3D rps and each segment of
waveform =3D roughly 2(brush width)*commutator contact
width. In my design, I even split the pack voltage to
allow for better slip and spaced unconnected
commutator so as to not short out the pack. I
figursed that combined with a servo controller I can
control the rotational speed. Unfortunately, I havent
had a chance to fab one yet.




> --- robert harder <[email protected]> wrote:
> 
> > =
> 
> ...


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## EVDL List (Jul 27, 2007)

oops! thats each segment of waveform =3D roughly 2(brush
width)+commutator contact width


> --- lyle sloan <[email protected]> wrote:
> 
> > Actually, you arent that off base. I had the same
> > notion awhile ago and asked some old radar techs
> ...


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## EVDL List (Jul 27, 2007)

I've been thinking quite a bit along these lines recently. Making
an electro-mechanical "commutator" that would attach to the
motor shaft and produce reasonably conditioned 3-phase power.
My idea is to stay away from brushes and contactors entirely,
but basically interface the shaft position to some power electronics
directly. I'd love to hear some feedback from the list on this one...

The motor shaft would have a drum attached whose surface is machined
in a fairly intricate manner. (I'm working on producing a drawing that I
can
link to -- ASCII art definitely won't do it on this one.) A bunch of Hall
effect 
sensors would be used to detect the surface of this drum and these Hall 
effect sensors would be used to switch some big mosfets. The pattern on
the drum would do two things -- first there would be the equivalent of PWM
to go from 0 to full on in a way consistant with a sine curve, second would 
be current reversal. You just put the sensors for each branch of the
3-phase
120 degrees apart on a housing that surrounds the drum. Finally, the
housing 
that holds the Hall effect sensors can be moved axially so that the PWM
profile
changes so that the peak voltages go from zero to full pack (that's your 
"gas pedal"). 

I know this probably sounds cludgy (and it may be all but impossible to 
understand without diagrams) but I started down this line of thought by
trying to come up with a solid state replacement for everyone's favorite
piece of 19th century technology -- the commutator. As I said before,
I don't have pictures of the full-on AC/3-phase idea, but here's a sketch
of an almost trivial implementation of ordinary PWM using these ideas.

http://www.southernct.edu/~fields/EV_Docs/electro-mechanical_PWM.pdf

Here's a vague indication of what half of a sine-wave would need to look
like on the encoding drum:

http://www.southernct.edu/~fields/EV_Docs/sine_wave_PWM.pdf

Cheers,
Joe




> Lee Hart wrote:
> >
> > robert harder wrote:
> >> Would it be possible to use a small DC motor using a low power DC
> ...


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## EVDL List (Jul 27, 2007)

> Joe Fields <[email protected]> wrote:
> > I've been thinking quite a bit along these lines recently. Making
> > an electro-mechanical "commutator" that would attach to the
> > motor shaft and produce reasonably conditioned 3-phase power.
> ...


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## EVDL List (Jul 27, 2007)

> Morgan LaMoore wrote:
> >
> > The problem is that for an AC induction motor, you don't want AC at
> > the mechanical rotation frequency, you want a slightly different
> ...


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## EVDL List (Jul 27, 2007)

> Morgan LaMoore wrote:
> > The problem is that for an AC induction motor, you don't want AC at
> > the mechanical rotation frequency, you want a slightly different
> > frequency. Also, for EV use, you probably want Flux Vector Control to
> ...


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## EVDL List (Jul 27, 2007)

Well, looking at all the details written, it seems that for a prototype or =
DIY project a DC motor used as the controller for an inductive AC could wor=
k, somewhat better than marginally.
=

It also adds up that the two motors would not /should not share a direct dr=
ive linkage. The small DC could first drive a larger commutator that maps t=
o the AC motor directly. Phaze angles and slippage is then fairly automatic=
. Could also map a more complex commutator if improvements are needed.
=

The acceleration profile of the dc should be similar to the AC under load. =
(load modification can be linked back though an automotive fan-clutch) Then=
next you can add noise suppression or waveform treatment, if you wish.
=

At some point later (and when you have saved up a couple thousand) you rip =
out the DC motorized-controller and get a technically competent AC controll=
er.
=

For me it could be a cheep way to get an AC powered vehicle up and running =
for chasis/handling/Power testing. =

=

Then later I already have the right size motor installed (if not the best m=
otor), so I only need the controller etc to complete final efficency and ra=
nge testing.
=

The hard part in this is providing the right controlling commutator. Someth=
ing left over from and even bigger dc motor with 3 circuit? This all makes =
sense to be if you have the parts laying about unused.



Arak Leatham - Web and Desktop Systems Developer




Estimating, Point of Sale, Tracking, Reporting Applications> Date: Wed, 5 D=
ec 2007 09:47:49 -0600> From: [email protected]> To: [email protected]=
> Subject: Re: [EVDL] economy ac controller> > Morgan LaMoore wrote:> > The=
problem is that for an AC induction motor, you don't want AC at> > the mec=
hanical rotation frequency, you want a slightly different> > frequency. Als=
o, for EV use, you probably want Flux Vector Control to> > give you proper =
torque control, and it would take a genius to figure> > that out mechanical=
ly.> > If you're going to experiment with AC motor controllers, it pays to =
do > some experiments to get a "feel" for what the theory all means in prac=
tice.> > When I started, I used an old audio amplifier as my "inverter". I =
used > it to drive small 24v AC induction motors (aircraft surplus, or ante=
nna > rotator motors). Inexpensive multimeters are fine for measuring volta=
ge > and current. I could easily generate various frequencies, voltages, an=
d > waveforms, and see how the motor responded. Nowdays, a PC with a sound =
> card could provide quite a versatile platform for this.> > Later, I moved=
up to a 4-channel audio amp with external power > transistors on a big hea=
tsink (because I kept blowing them up  to > drive bigger 2-phase and 3-p=
hase motors, car alternators, etc.> > I learned that AC induction motors ar=
e pretty forgiving. Wrong > frequency, wrong waveform, and wrong voltage ha=
ve a fairly mild effect > on efficiency. The motor tends to adapt by itself=
, much as a DC series > motor will adapt to the voltage and load applied to=
it. Things only get > bad if you make an abrupt change, or load it so heav=
ily that it "pulls > out" and stalls, or apply too much voltage for the fre=
quency.> > The complex sophisticated algorithms are only necessary if you w=
ant to > wrest the maximum possible efficiency out of the motor. But these =
> efficiency curves are pretty broad and flat. A square wave, for example, =
> only lowers efficiency about 10% compared to a perfect sinewave. A 2:1 > =
error in voltage (twice the voltage needed for a particular load) only > ca=
uses about a 5% loss (it mainly shifts the power factor).> > I think it's f=
airly simple to make an inexpensive AC drive that matches > the performance=
of a DC drive. However, that is not the direction that > most designers ha=
ve taken -- they seek to maximize performance and > efficiency. That extra =
10% or so in performance costs them dearly in > time and money! That may be=
justified if you are going to mass produce > millions of units; but not if=
you only want a few.> -- > Ring the bells that still can ring> Forget the =
perfect offering> There is a crack in everything> That's how the light gets=
in -- Leonard Cohen> --> Lee A. Hart, 814 8th Ave N, Sartell MN 56377, lee=
ahart_at_earthlink.net> > _______________________________________________> =
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## EVDL List (Jul 27, 2007)

> Arak Leatham wrote:
> > ... it seems that for a prototype or DIY project a DC motor used as
> > the controller for an inductive AC could work, somewhat better than
> > marginally.
> ...


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## EVDL List (Jul 27, 2007)

[No message]


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## EVDL List (Jul 27, 2007)

[No message]


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## EVDL List (Jul 27, 2007)

I think traditional 6 step is adequate for driving AC induction motors.
If we are winding the motor ourself we can wind them to prefer,
efficiency wise, this "squarish wave " pattern.

I think the switching losses can be less in the 6 step or trapezoidal
than the sinusoidal at the expense of low rpm smoothness.



PS. syncronous means no slip, ie not an induction motor. There must be a
field for this, permanent magnets or slip-ring driven coils. The prius
uses magnets(the most compact)
The insight and accord use salient pole syncronous PM motors, This means
the coils don't overlap in anyway. the BEMF waveform, which determines
how they should be driven is non-overlaping squarewave. This is pure
trapizoidial drive.

I think these are easier motors to start with. I have wanted to stack up
4 of them in place of the whole motor in an insight.

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## EVDL List (Jul 27, 2007)

Whoops, Morgan LaMoore's comment was completely right
and my response was not. I wasn't thinking of induction motors,
which blinded me to the presence of the word INDUCTION in
his note.

Sorry Morgan, you are right, I was wrong.

So to make the system I'm thinking of work we either have
to have a small dc motor that drives the inverter or 
a synchronous motor. I'm wondering how tough it would be
to replace the rotor on a big induction motor with a rig full of
those neodymium super magnets...

Cheers,
Joe




> Joe Fields wrote:
> >
> >
> >
> ...


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## EVDL List (Jul 27, 2007)

Can these be scaled up or modified?

http://curtisinst.com/index.cfm?fuseaction=cProducts.dspProductCategory&catID=8

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## EVDL List (Jul 27, 2007)

> Andre' Blanchard wrote:
> > How about this motor.
> > http://www.surpluscenter.com/item.asp?UID=2007120515423248&item=10-2111&catname=electric
> >
> ...


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## EVDL List (Jul 27, 2007)

> Jeff Shanab wrote:
> > I think traditional 6 step is adequate for driving AC induction motors.
> > If we are winding the motor ourself we can wind them to prefer,
> > efficiency wise, this "squarish wave " pattern.
> ...


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## EVDL List (Jul 27, 2007)

Is anyone building a kit like that now, or capable of it? When my cars are paid off, I'ld like to keep one or two and EV convert it.

Well maybe I'll review that when the time comes, things are changing fast. 

It seems that we could possibly find someday, that an affordable Hibrid conversion for automatic transmission cars exists. (under 3 grand) Then we just use the vehicles for 20years more! To hell with the automakers, until they wise-up!



Arak Leatham - Web and Desktop Systems Developer




Estimating, Point of Sale, Tracking, Reporting Applications> Date: Wed, 5 Dec 2007 22:38:23 -0600> From: [email protected]> To: [email protected]> Subject: Re: [EVDL] economy ac controller> > Jeff Shanab wrote:> > I think traditional 6 step is adequate for driving AC induction motors.> > If we are winding the motor ourself we can wind them to prefer,> > efficiency wise, this "squarish wave " pattern.> > Good point, Jeff. Of course, this assumes the person rewinding it does > some studying to determine how to reposition the coils in the slots to > accomplish this.> > > I think the switching losses can be less in the 6 step or trapezoidal> > than the sinusoidal at the expense of low rpm smoothness.> > That reminds me of another thing I wanted to mention. One of the hardest > things to get right in an AC drive is startup and low speed operation -- > the motor is forced to run at high slip, and is likely to vibrate and be > inefficient.> > So... for a cheap AC drive, use an!
automatic transmission, and idle the > traction motor. Use an automatic that has a locking torque converter, > and you won't lose any efficiency over a manual transmission. Idling the > motor also lets you use all the existing ICE accessories in a conversion.> -- > Ring the bells that still can ring> Forget the perfect offering> There is a crack in everything> That's how the light gets in -- Leonard Cohen> --> Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net> > _______________________________________________> For subscription options, see> http://lists.sjsu.edu/mailman/listinfo/ev
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## EVDL List (Jul 27, 2007)

*Re: [EVDL] economy Ac controller*

> Can these be scaled up or modified?
>
> http://curtisinst.com/index.cfm?fuseaction=cProducts.dspProductCategory&catID=8

Seems ~50kVA for 2min would be enough for most circumstances - my 
Ranger is under twice that much and is far from aerodynamic as well as 
being 4800lbs!

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] economy Ac controller*

Curtis does not sell to individual hobbiest. You have to buy from a
distributor only. For Example you might be able to get Rod of EV parts to
get them for you as he is a distributor. The Same goes for any of the
commercial AC Motors and Controllers. That is why people have to go to
Electro Automotive for Solectra or Azure as they are now call, or Victor of
Metric Mind for Semiens, Brussca, or MES-DEA. They don't want to. They want
to sell batches of product to distributors. They could not turn a profit or
build their product if they had to support sales to individuals who change
there minds. They also don't want to insure the individual is not going to
get hurt because they did not know what they were doing, or failed to follow
any specific laws of their region. Curtis does not make EV controller for us
on the list. They are building for Forklifts, Golf carts, and other EV OEM
utility vehicles. Same goes for most manufacturing. Try running up to an
Intel factory and buy the latest Quad core. Or Go to Black and Decker and
purchase their latest gadget.

So while the Spec's look good, consider then not available unless you can
find a distributor. I have checked in Phoenix and only one distributor in
the valley and he was hard to deal with at the time as he only wanted to
replace bad ones from OEM equipment. Not to help figure a way to make an AC
EV conversion.





> <[email protected]> wrote:
> 
> > > Can these be scaled up or modified?
> > >
> ...


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## EVDL List (Jul 27, 2007)

> Arak Leatham wrote:
> > Is anyone building a kit like that now, or capable of it?
> 
> I'm sure people are working on it. However, they won't be doing so at
> ...


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## EVDL List (Jul 27, 2007)

> I'm sure people are working on it. However, they won't be doing so at > any big company, because they will favor the higher-tech (and higher > profit) approaches.
Well no I wasn't putting any bets on the big boys. I know they want a reliable 300% profit with low risk.

> The problem is, when a "little guy" does it, he may get one for his own > use, but he's unlikely to sell it to anyone else. He won't have many > customers -- very few people buy kits.
Yes that's who I'm thinking of. As soon as the parts are available at 3k, I'm hoping to consult with the small guys or pay them to put it in.

I think maybe Properity.com or other micro lender may be talked into financing some of these conversions if the reliable vendors are out there and well published. 

After all, the batteries can be neglected, but the rest of the car could be good collateral for 30years since better packs (and parts) should continue to surface. The never-stop-idle idea definately opens it up to the generic install set.

That's why I'ld like to add a section for these small business visionaries to my advocacy website. If I do this addition, I'll be back here to pester you all insessently to complete the databank and give advise. (Heck I may even learn to spell for this great adventure.... strike that, I'll ask my wife or spell check, programmers are adverse to learning to speal) ;-)


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