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Discussion Starter #1
At work last week I got a chance to work on a 54KW light dimmer for
studio lighting. The dimmer is built much like an EV motor controller
except much simpler. The main difference is the load is lots of big
lights instead of a motor, and the dimmer doesn't have to product the
PWM chopper signal. The AC is already there, supplied via 480 volts
three phase on 750 circular mill cables with 400 amp fuses. All the
dimmer has to do is turn on at the desired fraction of the, already
existing, waveform for the desired output.

The interesting thing about all this is perspective. This very simple
54KW dimmer is built in a seven (7) foot tall 19 inch wide rack and
cost about a hundred thousand dollars.

Just though you might find this interesting.

Ken

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Discussion Starter #3
On 5 Nov 2007 at 23:01, Joseph T. wrote:

> How is it that an EV controller can controll more power,cost less, and
> be more compact?

Must be because all those nasty kleptomanical controller designers are
gouging us poor, defenseless EV hobbyists! <grin>

Sorry, I couldn't resist. In truth the EVDL debate over controller pricing
is probably eternal. If somehow hobbyist EV controllers, sold in the dozens
or hundreds, could be built so they cost one-half or one-third of what they
cost now, there are some who still wouldn't be satisfied. There will always
be those who think (or at least hope) that hobbyist EV controllers should
cost what a million-copy mass-produced, sweatship-built electronic gadget
(cell phone, computer, whatever) costs.

All one can say to those people is "Go for it - see if you can build one for
that price," and hope that someday one of them succeeds in so doing.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Discussion Starter #4
It uses the motor as an inductor and no-one cares about ripple.

The lighting controller must put out good enough quality power to
not flicker and no spikes to protect lighting investment.

Also I assume you can get more money out of lighting customers than
hobbiest? But I don't thing that factors as heavily into the cost as one
might think.(if it is the size of a computer rack, it has more
material,more stuff to be designed,tested, etc.

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Discussion Starter #5
The dimmer rack is physically large but it contains far less
electronics than an EV controller. It uses 18 SCRs and a bare hand full
of through-hole components on the power circuit board. It's only
inductor is a harmonic filter on the input line only. The output is
straight from the SCRs. Operationally, the output is a fraction of the
input waveform, varied from 0 to 100 percent. Both halves of the
waveform is switched and the switching occurs on the trailing edge of
the waveform. That allows the SCRs to turn off as the voltage crosses
zero. It is an extremely simple design. No processors of any kind. The
controls are slide pots, in a remote panel, that sends 0 to 10 volts DC
(depending on the slider position) to the power section circuit board.
That in turn sets the bias on a trigger transistor that matches where,
in the waveform, the SCR is to turn on.

It is big because there is lots of big heatsinks - it is not terribly
efficient. Also because it can be. There is usually lots more room in a
studio sound lock or equipment room than there is in a car. It also is
cheaper, easier to design and build, if you don't have size constraints.

The cost is in line with the broadcast industry and the manufacture
enjoys a fair market value. EV controllers are sold to a very small
market and, to exist, must squeeze a lot of stuff in a very small,
light weight space and exist on a very, very thin profit margin.

This technology is very mature. It has been around for a long time and
there are a lot of them in use. The cost of these dimmers are in line
with the industry. The contrast in complexity, size, weight and cost
between industrial motor controllers, broadcast light dimmers and EV
controllers is truely something to appreciate.

Ken



-----Original Message-----
From: Jeff Shanab <[email protected]>
To: [email protected]
Sent: Tue, 6 Nov 2007 7:46 am
Subject: Re: [EVDL] Perspective...



It uses the motor as an inductor and no-one cares about ripple.

The lighting controller must put out good enough quality power to
not flicker and no spikes to protect lighting investment.

Also I assume you can get more money out of lighting customers than
hobbiest? But I don't thing that factors as heavily into the cost as one
might think.(if it is the size of a computer rack, it has more
material,more stuff to be designed,tested, etc.


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Discussion Starter #6
Joseph T. wrote:
> How is it that an EV controller can control more power, cost less, and
> be more compact [than a 54kw theater light dimmer]?

Because it's built to meet different requirements.

- Size and weight: The EV controller *has* to be small and light.
Nobody cares how big or heavy the theater light dimmer is. All
else being equal, more material costs more money. The dimmer's
7-foot cabinet alone costs more than most EV controllers. EV
controllers don't even *have* a cabinet (the user is expected
to provide the box himself).

- Durability: A theater light controller is expected to last for
decades. Many have been there since the theater was built. In
contrast, most people are used to (and will only pay for) a few
year's reliability in consumer electronics like an EV controller.
Designing for a short life is a lot cheaper.

- Transients: The AC power line is very noisy. 1000 volt transients
are a daily occurrence, and 6000 volt spikes routinely occur
during thunderstorms. Equipment connected to them has to be able
to survive such transients.

- The Market: There is always the "charge what the traffic will bear"
school of marketing. The price is set by what the customer will pay,
rather than what it actually costs to produce.

--
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

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Discussion Starter #7
How about RFI? My Curtis controller shreads my AM radio. I'd be pretty unhappy with a theatrical lighting system that buzzed all over my sound system.



Steve


-----Original Message-----
From: Jeff Shanab <[email protected]>
To: [email protected]
Sent: Tue, 6 Nov 2007 5:46 am
Subject: Re: [EVDL] Perspective...




It uses the motor as an inductor and no-one cares about ripple.

The lighting controller must put out good enough quality power to
not flicker and no spikes to protect lighting investment.

Also I assume you can get more money out of lighting customers than
hobbiest? But I don't thing that factors as heavily into the cost as one
might think.(if it is the size of a computer rack, it has more
material,more stuff to be designed,tested, etc.

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Discussion Starter #8
[email protected] wrote:
> How about RFI? My Curtis controller shreads my AM radio.

The Curtis controllers themselves are relatively good with regards to
RFI. They deliberately switch rather slowly, which produces softer
switching edges and less RFI.

The problem comes when you connect long, wide-open, unshielded wires to
it. We've discussed this before (see the archives). The gist of it is
that you need to keep the wires short, pair them together, put them in
metal conduit, or put a braided shield over them. Ground the controller
case and motor. Put the various components in metal or shielded boxes
(batteries, contactors, etc.)
--
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

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Discussion Starter #9
Lee Hart wrote:
> > Ground the controller case and motor.
>
To chassis ground, or to traction negative? If to chassis ground, do
you ever run the risk this way of having the chassis with a path to the
traction pack (e.g., via motor dust)?

Thanks.

Bill Dennis

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Discussion Starter #10
Depending on how you need to arrange your dielectric, and especially how
your charger is hooked up and whether it is line isolated, etc, you can use
small capacitors to achieve RF ground without the danger of a DC fault and
power follow through.


On Tue, 06 Nov 2007 12:05:09 -0700, Bill Dennis wrote
> Lee Hart wrote:
> > > Ground the controller case and motor.
> >
> To chassis ground, or to traction negative? If to chassis ground,
> do you ever run the risk this way of having the chassis with a path
> to the traction pack (e.g., via motor dust)?
>
> Thanks.
>
> Bill Dennis
>
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Discussion Starter #11
Steve, an' EVerybody;

Ya may as well Forgetabout AM! EVery EV I EVer built even ones with a
contacter controller . They still picked up motor hash, or the brushes, as
ya went along. Nothin' on AM to be worth all the hassle to "fix" it anyhow.
FM works great! My Alpine radio that came with my 89 Jetta works perfectly
on FM, and the cassette player, too.Bee happy with FM<G>!

Seeya

Bob
----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Tuesday, November 06, 2007 1:26 PM
Subject: Re: [EVDL] Perspective...


>
> How about RFI? My Curtis controller shreads my AM radio. I'd be pretty
> unhappy with a theatrical lighting system that buzzed all over my sound
> system.
>
>
>
> Steve
>
>
> -----Original Message-----
> From: Jeff Shanab <[email protected]>
> To: [email protected]
> Sent: Tue, 6 Nov 2007 5:46 am
> Subject: Re: [EVDL] Perspective...
>
>
>
>
> It uses the motor as an inductor and no-one cares about ripple.
>
> The lighting controller must put out good enough quality power to
> not flicker and no spikes to protect lighting investment.
>
> Also I assume you can get more money out of lighting customers than
> hobbiest? But I don't thing that factors as heavily into the cost as one
> might think.(if it is the size of a computer rack, it has more
> material,more stuff to be designed,tested, etc.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
>
> ________________________________________________________________________
> Email and AIM finally together. You've gotta check out free AOL Mail! -
> http://mail.aol.com
> _______________________________________________
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> http://lists.sjsu.edu/mailman/listinfo/ev
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>
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Discussion Starter #12
Bob Rice <[email protected]> wrote:
> Steve, an' EVerybody;
>
> Ya may as well Forgetabout AM! EVery EV I EVer built even ones with a
> contacter controller . T

The radio on my EV works perfectly, on AM (LW and MW), and FM. Not
that I ever listen to AM radio..

Maybe there are some advantages to a factory built EV :)

http://www.tuer.org.uk/evs2/myev.html

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Discussion Starter #13
Lee Hart wrote:
>>> Ground the controller case and motor.

Bill Dennis asked:
>> To chassis ground, or to traction negative? If to chassis ground,
>> do you ever run the risk this way of having the chassis with a path
>> to the traction pack (e.g., via motor dust)?

Chassis ground. This is the best RF ground that you have.

George Swartz wrote:
> Depending on how you need to arrange your dielectric, and especially
> how your charger is hooked up and whether it is line isolated, etc,
> you can use small capacitors to achieve RF ground without the danger
> of a DC fault and power follow through.

If it is convenient to leave your motor ungrounded, then it is as good,
and in some cases better to ground the motor case through a good RF
capacitor, like 0.01uF ceramic. This has the advantage of not creating
DC leakage paths from carbon dust or a wet motor. However, this is
mechanically difficult; every mounting bolt has to be isolated (such as
with rubber mounts), and there needs to be some non-metallic coupler in
the shaft (such as a rubber spider coupler).

Though off-topic a bit, it's worth mentioning that most commercial EVs
and hybrids have a DC ground fault sensor. They serve the same purpose
as a GFCI for the AC charger -- to detect ground faults and prevent
operation until they are fixed.

A DC ground fault detector is harder to build, because you can't use a
simple current sensing transformer like the AC GFCI. The usual method is
to have a relay or electronic switch that alternately connects a large
value resistor from ground to the + end of the pack, then the - end of
the pack. If a DC voltage appears across this resistor, then there is a
ground fault somewhere that is completing the circuit and allowing
current to flow.
--
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

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Discussion Starter #14
It's a common practice on radio controlled cars and planes to put some
capacitors between commutator terminals and the case of the motor to
reduce EMI interference. Would this work on a EV too, or would it be
impractical?





Lee Hart <[email protected]> wrote:
> Lee Hart wrote:
> >>> Ground the controller case and motor.
>
> Bill Dennis asked:
> >> To chassis ground, or to traction negative? If to chassis ground,
> >> do you ever run the risk this way of having the chassis with a path
> >> to the traction pack (e.g., via motor dust)?
>
> Chassis ground. This is the best RF ground that you have.
>
> George Swartz wrote:
> > Depending on how you need to arrange your dielectric, and especially
> > how your charger is hooked up and whether it is line isolated, etc,
> > you can use small capacitors to achieve RF ground without the danger
> > of a DC fault and power follow through.
>
> If it is convenient to leave your motor ungrounded, then it is as good,
> and in some cases better to ground the motor case through a good RF
> capacitor, like 0.01uF ceramic. This has the advantage of not creating
> DC leakage paths from carbon dust or a wet motor. However, this is
> mechanically difficult; every mounting bolt has to be isolated (such as
> with rubber mounts), and there needs to be some non-metallic coupler in
> the shaft (such as a rubber spider coupler).
>
> Though off-topic a bit, it's worth mentioning that most commercial EVs
> and hybrids have a DC ground fault sensor. They serve the same purpose
> as a GFCI for the AC charger -- to detect ground faults and prevent
> operation until they are fixed.
>
> A DC ground fault detector is harder to build, because you can't use a
> simple current sensing transformer like the AC GFCI. The usual method is
> to have a relay or electronic switch that alternately connects a large
> value resistor from ground to the + end of the pack, then the - end of
> the pack. If a DC voltage appears across this resistor, then there is a
> ground fault somewhere that is completing the circuit and allowing
> current to flow.
> --
> 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
>



--
www.electric-lemon.com

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Discussion Starter #15
The ground fault protectors for PV systems use a 1/2 amp DC circuit
breaker, which is ganged to a 60 or 80 or whatever amp circuit
breaker. The amp amp breaker is wired between the nuetral and the
ground, so if it detects any current flow there, it trips, and turns
off the hot leg. There is a resistor in parallel with the 1/2 amp
breaker, so if it trips, there is still a high resistance ground, just
not a solid ground.

This scheme is obviously designed to work with a grounded DC system,
so I don't think it would be applicable to the floating DC system of
most EV's.

Z

>
> Though off-topic a bit, it's worth mentioning that most commercial EVs
> and hybrids have a DC ground fault sensor. They serve the same purpose
> as a GFCI for the AC charger -- to detect ground faults and prevent
> operation until they are fixed.
>
> A DC ground fault detector is harder to build, because you can't use a
> simple current sensing transformer like the AC GFCI. The usual method is
> to have a relay or electronic switch that alternately connects a large
> value resistor from ground to the + end of the pack, then the - end of
> the pack. If a DC voltage appears across this resistor, then there is a
> ground fault somewhere that is completing the circuit and allowing
> current to flow.

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Discussion Starter #16
Peter Gabrielsson wrote:
> It's a common practice on radio controlled cars and planes to put some
> capacitors between commutator terminals and the case of the motor to
> reduce EMI interference. Would this work on a EV too, or would it be
> impractical?

Yes, that will work with a big series DC motor, too. The challenge is
that it needs to be a pretty good capacitor (very low ESR) or it won't
be able to "fight off" the low impedance of the armature.

--
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

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