DC v. AC

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DC v. AC

Andrew Wood-13
Ive been doing some research into EVs and understand fairly well now the
issues involved with DC based systems but I've been struggling to find
much info on AC systems - other than books which state AC to be the
superior choice for the future, then carry on talking about how to do it
with DC.

As a first timer Im a little unsure whether to invest in an AC system or
a DC system, am I right in thinking that with AC I can get the same
performance with a lower voltage -i.e less batteries?

Furthermore is the normal approach with AC to keep the voltage to the
motor constant and vary speed by changing the frequency?

Andrew

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Re: DC v. AC

Lee Hart
Andrew Wood wrote:
> As a first timer I'm a little unsure whether to invest in an AC
> system or a DC system, am I right in thinking that with AC I can get
> the same performance with a lower voltage -- i.e. less batteries?

For your first EV, it's better to stick with a DC system. It costs less,
and is easier to get working. If all goes well, you can sell the DC
parts and move up to AC later.

If by "performance" you mean speed and acceleration, this is not a
function of AC vs. DC. It is simply a matter of the mechanical
horsepower that the motor/controller/batteries can deliver.

Likewise, this kind of performance is not directly linked to pack
voltage. As long as you pick the motor and controller to match the pack
voltage, you can get any performance level desired. A 72v 1000a system
has the same horsepower, speed, and acceleration as a 144v 500a or 288v
250a system -- all deliver 72kw (which is about 72 horsepower) max.

As a rule, the motors and controllers that are the easiest to get will
be in the 100-300v range. DC systems tend to be on the lower end, and AC
systems tend to be on the upper end of this range.

> Furthermore is the normal approach with AC to keep the voltage to the
> motor constant and vary speed by changing the frequency?

No. For both AC and DC motors, voltage primarily controls speed, and
current primarily controls torque. The controller's job is to step down
the pack voltage to whatever the motor needs to run at the desired
speed. It also limits the current to whatever is needed to produced the
desired torque.

All motors are really AC. A "DC" motor has an internal inverter (the
commutator) that converts the applied DC into AC to make it run. The
frequency needed is proportional to speed. The DC motor produces the
right frequency automatically. An external inverter (used with an AC
motor) has to adjust the frequency itself based on motor speed.

--
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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Re: DC v. AC

Morgan LaMoore
In reply to this post by Andrew Wood-13
Andrew,

No, AC systems usually use higher voltage, not lower voltage. This is
a design choice for the motor designer, though, not something inherent
to the technology.

A good AC system will vary voltage, frequency, and phase to control
current to get as high efficiency as possible. The voltage and speed
are still usually proportional, though.

With an AC system, you will spend more money for the same performance,
but you will get slightly higher efficiency and regenerative braking.
DC systems are widely available and relatively inexpensive due to the
forklift industry; there's no equivalent AC motor source that we can
take advantage of.

-Morgan LaMoore

On Fri, May 1, 2009 at 3:58 PM, Andrew Wood <[hidden email]> wrote:

> Ive been doing some research into EVs and understand fairly well now the
> issues involved with DC based systems but I've been struggling to find
> much info on AC systems - other than books which state AC to be the
> superior choice for the future, then carry on talking about how to do it
> with DC.
>
> As a first timer Im a little unsure whether to invest in an AC system or
> a DC system, am I right in thinking that with AC I can get the same
> performance with a lower voltage -i.e less batteries?
>
> Furthermore is the normal approach with AC to keep the voltage to the
> motor constant and vary speed by changing the frequency?
>
> Andrew
>
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>

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Re: DC v. AC

Andrew Wood-13
Thanks Morgan

I guess DC is the best choice then.


What Im looking at using is:

FB1-4001A motor
Trojan 27TMH 12v batteries (10 to give 120v)

I was looking at a Zilla controller but they seem to have stopped making
them so Im opting for a Curtis instead.

Would this be reasonable?

Regards
Andrew


Morgan LaMoore wrote:

> Andrew,
>
> No, AC systems usually use higher voltage, not lower voltage. This is
> a design choice for the motor designer, though, not something inherent
> to the technology.
>
> A good AC system will vary voltage, frequency, and phase to control
> current to get as high efficiency as possible. The voltage and speed
> are still usually proportional, though.
>
> With an AC system, you will spend more money for the same performance,
> but you will get slightly higher efficiency and regenerative braking.
> DC systems are widely available and relatively inexpensive due to the
> forklift industry; there's no equivalent AC motor source that we can
> take advantage of.
>
> -Morgan LaMoore
>
> On Fri, May 1, 2009 at 3:58 PM, Andrew Wood <[hidden email]> wrote:
>  
>> Ive been doing some research into EVs and understand fairly well now the
>> issues involved with DC based systems but I've been struggling to find
>> much info on AC systems - other than books which state AC to be the
>> superior choice for the future, then carry on talking about how to do it
>> with DC.
>>
>> As a first timer Im a little unsure whether to invest in an AC system or
>> a DC system, am I right in thinking that with AC I can get the same
>> performance with a lower voltage -i.e less batteries?
>>
>> Furthermore is the normal approach with AC to keep the voltage to the
>> motor constant and vary speed by changing the frequency?
>>
>> Andrew
>>
>> _______________________________________________
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>>
>>    
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Re: DC v. AC

Thos True
I am thinking that you would be much happier with the logitech 120 - 156
volt controller. There are 3 models to choose from I am planning to use the
750 Amp unit ( part # CT2411 at evparts.com) for an upcoming 120 volt
project.
Best of luck on your project -Thos

On Fri, May 1, 2009 at 2:27 PM, Andrew Wood <[hidden email]> wrote:

> Thanks Morgan
>
> I guess DC is the best choice then.
>
>
> What Im looking at using is:
>
> FB1-4001A motor
> Trojan 27TMH 12v batteries (10 to give 120v)
>
> I was looking at a Zilla controller but they seem to have stopped making
> them so Im opting for a Curtis instead.
>
> Would this be reasonable?
>
> Regards
> Andrew
>
>
> Morgan LaMoore wrote:
> > Andrew,
> >
> > No, AC systems usually use higher voltage, not lower voltage. This is
> > a design choice for the motor designer, though, not something inherent
> > to the technology.
> >
> > A good AC system will vary voltage, frequency, and phase to control
> > current to get as high efficiency as possible. The voltage and speed
> > are still usually proportional, though.
> >
> > With an AC system, you will spend more money for the same performance,
> > but you will get slightly higher efficiency and regenerative braking.
> > DC systems are widely available and relatively inexpensive due to the
> > forklift industry; there's no equivalent AC motor source that we can
> > take advantage of.
> >
> > -Morgan LaMoore
> >
> > On Fri, May 1, 2009 at 3:58 PM, Andrew Wood <[hidden email]> wrote:
> >
> >> Ive been doing some research into EVs and understand fairly well now the
> >> issues involved with DC based systems but I've been struggling to find
> >> much info on AC systems - other than books which state AC to be the
> >> superior choice for the future, then carry on talking about how to do it
> >> with DC.
> >>
> >> As a first timer Im a little unsure whether to invest in an AC system or
> >> a DC system, am I right in thinking that with AC I can get the same
> >> performance with a lower voltage -i.e less batteries?
> >>
> >> Furthermore is the normal approach with AC to keep the voltage to the
> >> motor constant and vary speed by changing the frequency?
> >>
> >> Andrew
> >>
> >> _______________________________________________
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> >> Usage guidelines: http://evdl.org/help/index.html#conv
> >> Archives: http://evdl.org/archive/
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> >>
> >>
> >>
> >
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> >
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Re: DC v. AC

Willie McKemie
On Fri, May 01, 2009 at 06:38:03PM -0700, Thos True wrote:
> I am thinking that you would be much happier with the logitech 120 - 156

Logisystem?

--
Willie, ONWARD!  Through the fog!
http://counter.li.org Linux registered user #228836 since 1995
Debian3.1/GNU/Linux system uptime  503 days 15 hours 22 minutes

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Re: DC v. AC

EVDL Administrator
In reply to this post by Andrew Wood-13
On 1 May 2009 at 22:27, Andrew Wood wrote:

> What Im looking at using is:
>
> FB1-4001A motor
> Trojan 27TMH 12v batteries (10 to give 120v)

Long experience says that you'll be lucky to get a year's worth of service
from those batteries.  They're meant for operating lights and trolling
motors. They're not at all suited to the very high currents that your
proposed drive system will require from them.  

If you can't fit 20 golf car batteries into your glider, you might try 15 8-
volt golf car batteries.  They won't last as long as 6v golf car batteries,
but they'll be a considerable improvement over the 12v marine batteries.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: DC v. AC

Thos True
In reply to this post by Willie McKemie
I stand corrected. Over the last several years, we have used one of their
controllers on our wild(e) golf cart, and I had been under the impression
that it was called a logitech. After going back to the site, I see my goof.
Thank you for noticing! -Thos

On Fri, May 1, 2009 at 7:23 PM, Willie McKemie <[hidden email]> wrote:

> On Fri, May 01, 2009 at 06:38:03PM -0700, Thos True wrote:
> > I am thinking that you would be much happier with the logitech 120 - 156
>
> Logisystem?
>
> --
> Willie, ONWARD!  Through the fog!
> http://counter.li.org Linux registered user #228836 since 1995
> Debian3.1/GNU/Linux system uptime  503 days 15 hours 22 minutes
>
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Re: DC v. AC

Andrew Wood-13
In reply to this post by EVDL Administrator
So 6v batteries are better than 12v then?

Id like to buy from Trojan because I know I can get those easily in the
UK, but looking on the golf cart section of their website
(http://www.trojanbattery.com/Products/GolfCart.aspx) there is a lot to
choose from is one particularly better than the others?

Im spoilt for choice with all these parts to choose from!

Andrew

EVDL Administrator wrote:

> On 1 May 2009 at 22:27, Andrew Wood wrote:
>
>  
>> What Im looking at using is:
>>
>> FB1-4001A motor
>> Trojan 27TMH 12v batteries (10 to give 120v)
>>    
>
> Long experience says that you'll be lucky to get a year's worth of service
> from those batteries.  They're meant for operating lights and trolling
> motors. They're not at all suited to the very high currents that your
> proposed drive system will require from them.  
>
> If you can't fit 20 golf car batteries into your glider, you might try 15 8-
> volt golf car batteries.  They won't last as long as 6v golf car batteries,
> but they'll be a considerable improvement over the 12v marine batteries.
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
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> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
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Re: DC v. AC

Lee Hart
Andrew Wood wrote:
> So 6v batteries are better than 12v then?

The 6v batteries *we can get* are better than the 12v batteries *we can
get*.

The 6v batteries are made for golf carts, which really are an electric
vehicle. So, they are designed for high currents (75 amps is the
standard test load), and long life in deep cycle applications (600
cycles to 80% depth of discharge is common).

12v batteries are almost all designed for engine starting applications.
They can deliver high currents, but only for a few seconds at a time.
Their cycle life is terrible (a few dozen cycles to 80% depth of
discharge is typical). These are called SLI (for Starting Lighting and
Ignition) and are worthless in EVs.

Some 12v batteries are designed for deeper discharges. 25 amps is the
standard test load, and they typically last around 200 cycles. These
batteries are sold for boat trolling motors, industrial devices such as
floor sweepers, computer UPS units, and recreational vehicles to supply
small amounts of 12v power for a few hours.
--
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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Re: DC v. AC

Evan Tuer
In reply to this post by Andrew Wood-13
On Sat, May 2, 2009 at 11:04 AM, Andrew Wood <[hidden email]> wrote:
> So 6v batteries are better than 12v then?
>

What are you converting?

> Id like to buy from Trojan because I know I can get those easily in the
> UK,

They may be easy to get but I'd be surprised if they're good value,
considering they're imported from the US in pretty small quantities.

Therefore most UK cars end up with either "serious" traction batteries
(pretty expensive), or an Exide sealed battery of some sort.

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Re: DC v. AC

Andrew Wood-13
A mini, hence Im limited on space.

Looking at the Amp/hr rating the Trojan batteries appear to be good
value compared to the others Ive seen on websites such as
everything-ev.com & evparts.com

If DC is the best ,why do the 'big' manufacturers only produce AC systems?

Andrew


Evan Tuer wrote:

> On Sat, May 2, 2009 at 11:04 AM, Andrew Wood <[hidden email]> wrote:
>  
>> So 6v batteries are better than 12v then?
>>
>>    
>
> What are you converting?
>
>  
>> Id like to buy from Trojan because I know I can get those easily in the
>> UK,
>>    
>
> They may be easy to get but I'd be surprised if they're good value,
> considering they're imported from the US in pretty small quantities.
>
> Therefore most UK cars end up with either "serious" traction batteries
> (pretty expensive), or an Exide sealed battery of some sort.
>
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Re: DC v. AC

Lee Hart
Andrew Wood wrote:
> If DC is the best, why do the 'big' manufacturers only produce AC systems?

In fact, the 'big' manufacturers produce nothing at all! They've built a
few prototype EVs with AC systems, but sold a negligible number of them.
Almost all the EVs actually on the road are DC systems, built by small
companies and individuals.

Why did the big auto companies use AC for their EVs? There are many reasons.

  - it's easier to "sell" customers on it (oh boy, high tech)!
  - the engineers wanted to play with AC
  - they could borrow technology from industrial AC drives
  - maintenance might be less (no brushes)
  - AC motors can be cheaper (though the inverters cost more)
  - AC might be more efficient
  - it's easier to add features like regenerative braking
  - water cooling is easier (and the auto companies like water cooling)

--
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
--
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Re: DC v. AC

Evan Tuer
In reply to this post by Andrew Wood-13
On Sat, May 2, 2009 at 12:08 PM, Andrew Wood <[hidden email]> wrote:
> A mini, hence Im limited on space.

Hmm, and weight capacity.  Quite a few people have attempted mini EVs,
personally I don't think they're a great choice.

> Looking at the Amp/hr rating the Trojan batteries appear to be good
> value compared to the others Ive seen on websites such as
> everything-ev.com & evparts.com

Fair enough, if they are really suitable for EV use.

> If DC is the best ,why do the 'big' manufacturers only produce AC systems?

DC isn't "the best".  It traditionally represents good value for money
for a DIY conversion since you can use mass-produced components made
for forklifts, and there are high power controllers available more
cheaply than AC (there's only 1/3rd of the silicon needed).

The big manufacturers don't only produce AC systems - the most common
production EVs in Europe used brushed DC motors.

However, time moves on and a modern EV would definitely use an AC or
BLDC system these days, as there are many  advantages and the price
difference of the controller is decreasing as electronic components
get cheaper and more powerful.

Even forklifts use AC now.  You could probably consider a Curtis or
Zapi AC controller and motor for your mini, without having to import
them yourself.

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Re: DC v. AC

George Swartz
In reply to this post by Lee Hart

Lee,

Your emails are dated 2008 ane coming in 100 pages back in my email stack.  
Please correct the time and date on your computer.  Your contribution here
is too important to be buried.

George




On Sat, 31 May 2008 09:18:51 -0400, Lee Hart wrote

> Andrew Wood wrote:
> > So 6v batteries are better than 12v then?
>
> The 6v batteries *we can get* are better than the 12v batteries *we
> can get*.
>
> The 6v batteries are made for golf carts, which really are an
> electric vehicle. So, they are designed for high currents (75 amps
> is the standard test load), and long life in deep cycle applications
> (600 cycles to 80% depth of discharge is common).
>
> 12v batteries are almost all designed for engine starting
> applications. They can deliver high currents, but only for a few
> seconds at a time. Their cycle life is terrible (a few dozen cycles
> to 80% depth of discharge is typical). These are called SLI (for
> Starting Lighting and Ignition) and are worthless in EVs.
>
> Some 12v batteries are designed for deeper discharges. 25 amps is
> the standard test load, and they typically last around 200 cycles.
> These batteries are sold for boat trolling motors, industrial
> devices such as floor sweepers, computer UPS units, and recreational
> vehicles to supply small amounts of 12v power for a few hours.
> --
> 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
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
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Re: DC v. AC

Lee Hart
George Swartz wrote:
> Lee,
>
> Your emails are dated 2008 ane coming in 100 pages back in my email stack.  
> Please correct the time and date on your computer.  Your contribution here
> is too important to be buried.

Sorry about that. Those posts came from my old laptop. It apparently has
a bad CMOS battery.

--
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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Re: DC v. AC

Jeff Shanab
In reply to this post by Andrew Wood-13
<flamebait>
   All motors run on AC
</flamebait>

They are either internally commutated or externally commutated :-)

The series DC motor comes from the forklift industry(and golf cart). It
makes it more available to us converters. It is designed for low voltage
operation. which is higher amps, but controllers are available.
Mostly we can buy 1 piece at a time from various vendors.
One of the failure modes in such a system is FULL ON. If the chances are
1 in 100,000 and you are selling 500,000 there is a possible /percieved
liability issue.
Brushes are a finicky beast. duty cyle and amps and the air's moisture
make a difference on wear. While it often seems auto companies would
love to have a regular repair item, the variablily is a nightmare for
warentees. Brushes and commutators, limit voltage and rpm.

AC motors are usually 3 phase and sealed. If you are making 1000's of
them, they are cheaper to make. They can easily be water cooled which
opens up packaging options. No brushes opens up the rpm and voltage
choices and means you can run at a higher rpm and gear it down. Which
lowers overall material costs and phase amps. The trade off is a need
for higher volts and much more intelligence in the controller. The
controller must be programmed or matched to the motor. This leads mostly
to a systems approach.  You have to buy everything all at once.  For
lightweight conversions, the total price difference is not much. The
exception is the higher voltage pack, if done with sealed batteries
needs more management $.

The AC motor controller failure mode is to stop turning, no launching
over someone in a cross walk. (this is again partially perceived because
an error in the software or the controller board can tell the power
section to do it anyway)

To meet what the auto manufactures feel is one of a many requirements,
ie >100 mile range,  they want to use lithium-ion(advanced) batteries.
These cells generally like lower amps and higher voltage and they get to
save on all that wire weight and extra handling of the heavy wire.


I think it is mostly a production scalability issue. If you are making
thousands, you have to sub-contract out the motor or make them yourself,
The AC can be lighter, less copper $$ and less iron $ and made with less
human labor. Big Saving when you are making 1000's.


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Re: DC v. AC

EVDL Administrator
In reply to this post by Lee Hart
On 31 May 2008 at 9:30, Lee Hart wrote:

> Why did the big auto companies use AC for their EVs? There are many reasons.

One more.  Big companies have lots of lawyers hanging around, and they get
twitchy about liability.  This is probably justified, especially with a
whole corps of stakeholders just waiting to pounce on any new and different
idea and tramp it into the ground.

"Unintended acceleration" is one of their favorites.  Twenty or 25 years
ago, the critics did a pretty fair job of crucifying the Audi 5000 with that
phrase, and it wasn't even a particularly innovative vehicle.  

(The Audi 5000 may indeed have deserved that fate.  I have no way of being
sure.  But if so, there were other similar products from the same company
which may have had the same flaw but were not similarly treated.  And
besides, such a discussion is WAY off topic for this list.  Remember, if you
convert a flawed vehicle, ICE-related weaknesses and hazards disappear with
the ICE -- and are replaced with whatever new weaknesses and hazards that
you and your new drive system create!  ;-)

Back on topic : as Lee pointed out, with AC drive, the commutation is in the
controller.  Without that, the motor goes nowhere.  So, when an AC
controller fails, the motor usually stops. (Maybe abruptly.)  But when a DC
controller fails, the motor often goes -- full speed ahead!  

This is not to say that DC systems can't be made safe.  There are ways of
building in multiple safeguards that will shut down the vehicle (in time,
one hopes) if they detect a runaway in progress.  

I should point out though, while we're on the subject, that this is a weak
point in many hobbyist EVs.  

Most low cost DC controllers have minimal runaway safeguards, typically
limited to a switch on the potbox (the KSI enable line is largely useless
for this purpose).  And sometimes hobbyists don't even apply such minimal
features properly.  They don't connect the potbox microswitch to a safety
contactor, for example, because they don't like the click-clack with every
press and release of the accelerator.  

They may fit a cable-operated main breaker to the EV, but they don't test it
regularly.  When they need it, the cable breaks, or is out of adjustment and
doesn't pull far enough.  

Or they intend to fit safeguards, but in the excitement of >finally< having
a running EV, they put that job off until it's too late.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: DC v. AC

Chris Zach
In reply to this post by Jeff Shanab
To hop into the discussion myself (a person who has spent the last year
or two repairing a particular type of AC motor controller and getting
very intimate with it's features) I think I can add something here.

One of the other reasons AC "controllers" cost more than DC might be
because the AC "motor controller" does a lot more than just control the
motor.

Let's compare the GM/Hughes Dolphin motor controller with something like
a Curtis 1231 controller for DC motors. Both do the following:

Control motor speed from 0 RPM to max
Provide a 50kw peak output

However the Dolphin also does the following additional things.

For the motor:
   Monitors the IGBT gate voltage and currents carefully and will shut
   down if it detects a problem.

   Monitors motor speed and changes torque profile with motor speeds.

   Provides motor reversing without outside support

   Can provide 3 user-selectable torque curves in "forward" and one in
   "reverse" which map well to an ICE car's PRNDL selections

   Provides regen as well as brake pot sensors for monitoring how hard
   thee brake pedal is being pressed for dynamic regen.

   Provides a slight amount of regen to simulate "engine drag" when you
   let off the throttle (depending on the virtual "gear" selected)

   Monitors temperatures and can run in reduced power mode if needed
  (with indicator)

For the "house circuits"
   Monitors current in and out of the battery and drives a "Fuel gauge"

   Monitors water temperature and can cycle the radiator fan as needed

   Monitors overall state and can cycle the water pump as needed

   Monitors water, IGBT, and motor temperatures and drives a "water temp
   gauge"

For safety's sake
   Monitors two separate throttle POTs and will shut down if there is a
   correlation error between them.

   Monitors a high voltage loop circuit and will shut down if it is
   breached (signaling unsafe exposed voltages)

   Can monitor a switch to shut down in the event of excessive G forces.

   Monitors for isolation faults in the motor and battery pack

   Has control over the contactors.

Nifty stuff:
   Has a built-in charger for conductive charging
   Has a built-in 100 amp DC-DC converter
   Has circuitry to pre-charge the HV capacitor rail
   Same circuitry to discharge the HV capacitor rail
   Full control over the main contactors

As well as a whole in-house processor system to allow fault diagnostics
and monitoring of the whole car's performance via CAN or RS232 interface
devices.

That's a lot of extra stuff over the standard Curtis. Now when you start
getting into Zilla territory many of these things are included. But a
Zilla 1k+PFC is starting to get into the expensive category.

I would posit that making a simple AC vector motor controller that
doesn't do any of the neat stuff should not be that expensive anymore.
There has been a lot of progress in the past 15 years: One can do all of
the IGBT drive and monitoring functions with a single chip these days.
You don't need a MACH-220+DSP to handle sequencing and the like, simple
chips can do the job. But it's the integration of all the other nice
"stuff" that IMO makes the AC systems nice.

Chris

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Re: DC v. AC

Victor Tikhonov
In reply to this post by Evan Tuer
Evan Tuer wrote:
>
> The big manufacturers don't only produce AC systems - the most common
> production EVs in Europe used brushed DC motors.

If you're talking about on-road EVs (not wheel chairs fork lifts golf
carts and such), this statement is not accurate. This would be the case
may be 30 years ago, but not today.

> However, time moves on and a modern EV would definitely use an AC or
> BLDC system these days, as there are many  advantages and the price
> difference of the controller is decreasing as electronic components
> get cheaper and more powerful.

Yes, time have moved on already. IIRC, only Peugeot 106 was high volume
production EV that used SepEx DC system. Even AC systems with induction
motors are considered old fashion AC choice as having lower efficiency
and narrower full torque band than, say synchronous machines.

Victor

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