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Re: [EVDL] Overdiven 10hp AC

We say AC motor as if all AC motors are the same. Most of our
generalizations are about the ACIM, AC InductionMotor. (pssst, all
motors run on AC)
If someone can get there hands on a wound rotor slip ring AC motor in
the size we need for drag racing, well the race would be on!

ACIM motors are designed for one speed and more importantly one level
of slip. The reactance of the rotor is a compromise.
If you instead have a three phase slip ring tap on the wound rotor, you
can vary the reactance, even inject voltage to lock in syncronous. You
can get regenerate the slip energy and get 10X starting torque at less
than run amps.

I have books, but I couldn't find a good online reference. Most give
speed torque curves, but the important is when they overlay the amps on it.

http://en.wikipedia.org/wiki/Electric_motor



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Re: [EVDL] Overdiven 10hp AC

 

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Re: [EVDL] Overdiven 10hp AC

> Exactly. Just as for ICEs, liquid cooling increases the power-to-weight> ratio. It's not AC vs. DC; it's that the AC motor example happens to be> liquid cooled, and all the DC examples were air-cooled.
I'ld think the only way you are going to get 'contactive' liquid cooling on a DC motor is to use brushless DC. The oil can't be good when used with arching brushes.

But those are just as expensive to implement as the AC's I'll guess.

But that does beg the question. WHY are they so much more than DC? Just because?



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Re: [EVDL] Overdiven 10hp AC

> ACIM motors are designed for one speed and more importantly one level
> of slip. The reactance of the rotor is a compromise.

You say ACIM as if all ACIM motors are the same. Industrial ACIM
motors are designed for one speed and one level of slip, but an ACIM
like the AC-150 is designed for 0 to 13000 RPMs at variable torque and
slip. It gets great performance because of that, but it also made it
much, much harder to design and requires more complicated controller.

That said, I don't know why people think a DSP and more silicon on an
induction motor controller is a bad thing. A DSP is about $10. The
extra silicon is expensive, but it's also a much more efficient
commutation system than brushes.

And yeah, other variants of AC motors (permanent magnet and slip ring)
are much easier to control than ACIM. They still require 3-phase
controller hardware, but it's easier to decide what signal to send:
just provide a sine wave of the desired voltage synchronized with the
mechanical rotation. There's no complications of deciding how much
slip to employ at the desired torque and speed or anything like that.
However, permenant magnets are expensive, and slip rings share some of
the same inefficiencies as DC (although they can do regen more easily
and are more efficient).

-Morgan LaMoore

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Re: [EVDL] Overdiven 10hp AC

google doesn't find much on a lincon motor. got link?

5hp may be too little. a larger alternator perhaps. from a semi or worse.
cool project on the kart. do you have pictures of the electronics?
also a video on youtube of it driving would be cool

Dan

Arak Leatham wrote:

>Nice chart, could you find a spec for any Lincon Liquid cooled to add in? Also a column for AC vs DC? I can't tell if the Etek is the DC or AC replacement. I'm guessing it's the DC from the RPM. B&S now only makes the AC, I believe.
>
>Also, I've hear of a place in oregon that has been converting auto-alternators to 5HP AC motors. This is for electric go-carts. If any one is interested, I'll locate thier website. OK well this is the cart.. http://www.austinev.org/evalbum/876
>
>
>

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Re: [EVDL] Overdiven 10hp AC

>If you have an inverter grade 10hp ac motor, like say from a CNC mill,
>Then you can push the hz higher and cool the losses you have and do>well. They are often water cooled already. >something like this(a little big) which gives 1500/6000 rpm means it>was made for VFD. 15hp cont,20hp 30min means a lot more! for 10seconds>ebay>130158862063 or 130158876810 >or a pair of these 170152432843
MAN! those first two are huge! The last one is more like it.

If Direct liuid cooling works as advertized I'l want something like two 1hp servos converted to 10hp continuous each. Although that is 2x the hp that I acually need.

I need to see if Lincon has such an offering yet...anyone have a R&D contact there?

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Re: [EVDL] Overdiven 10hp AC

From: Arak Leatham
> I'd think the only way you are going to get 'contactive' liquid cooling
> on a DC motor is to use brushless DC. The oil can't be good when used with
> arcing brushes.

A liquid-cooled DC motor does not run the brushes in the liquid; only the windings and iron (which produce most of the heat) are liquid cooled.

There are three sources of heat in an electric motor. Resistive losses (from the resistance of the copper windings and brushes or slip rings if it has them), magnetic losses (hysteresis, magnetization, and core loss in the iron), and mechanical friction (bearings, wind resistance, internal fans, brush drag, etc.)

All practical motors are AC; a "DC" motor is just an AC motor with an internal DC-to-AC converter. An AC motor's published specs are slightly better than an equivalent DC motor only because the latter includes the size, weight, and efficiency of this internal DC-to-AC converter. The AC motor "hides" these losses in its external inverter.

For those that think a commutator and brushes are inefficient, consider this. If they were inefficient, they would burn up! But they don't -- brushes and commutators are surprisingly small and have relatively little cooling compared to the transistors in solid-state inverters. A brush has a 1-2 volt drop; the IGBTs used in most inverters have a 2-3 volt drop, and so are actually somewhat *less* efficient. We use them because they have other advantages; not because they are more efficient.

> But that does beg the question. WHY are they so much more than DC? Just
> because?

A standard off-the-shelf AC induction motor of a given horsepower is slightly smaller and cheaper than an equivalent DC motor, because it doesn't have the brushes or commutator. Otherwise, the two types have virtually identical materials and efficiencies.

But if you want an AC traction motor for an EV, everything changes. The motor uses better bearings, stronger materials, and better balancing to withstand 13,000 rpm instead of 3600 rpm. The windings are laboriously hand-packed to increase efficiency instead of being machine-wound. More expensive core material is used to allow higher frequency operation. The insulation is strengthened to withstand the higher voltages and temperatures produced by higher peak loads. The cooling system is considerably improved.

By the time they get done, not one single piece is the same as a stock AC motor. Now you have a hand-made motor, custom produced in very low quantities. No wonder it is expensive!


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Re: [EVDL] Overdiven 10hp AC

 

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Re: [EVDL] Overdiven 10hp AC

--- Jeff Shanab <[email protected]> wrote:
<snip>
> If someone can get there hands on a wound rotor slip
> ring AC motor in
> the size we need for drag racing, well the race
> would be on!
<snip>

A lot of 3 phase 400 Hz Aircraft Alternators are wound
rotors. Not efficient, but usually designed for High
RPMs and low weight. Almost always will need a new
shaft, though. They are designed so that a short
circuit will snap the shaft, rather than stall the
engine turning it.

- Steven Ciciora


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Re: [EVDL] Overdiven 10hp AC

> You say ACIM as if all ACIM motors are the same. Industrial ACIM
> motors are designed for one speed and one level of slip, but an ACIM
> like the AC-150 is designed for 0 to 13000 RPMs at variable torque and
> slip. It gets great performance because of that, but it also made it
> much, much harder to design and requires more complicated controller.
The higher quality materials used allow for different slip levels, even the rotor design can be made to have different characteristics at differnt slip levels by taking advantage of the fact that the depth of the magnetic penetration into the rotor is related to slip frequency.
> That said, I don't know why people think a DSP and more silicon on an
> induction motor controller is a bad thing. A DSP is about $10. The
> extra silicon is expensive, but it's also a much more efficient
> commutation system than brushes.
>
> And yeah, other variants of AC motors (permanent magnet and slip ring)
> are much easier to control than ACIM. They still require 3-phase
> controller hardware, but it's easier to decide what signal to send:
> just provide a sine wave of the desired voltage synchronized with the
> mechanical rotation. There's no complications of deciding how much
> slip to employ at the desired torque and speed or anything like that.
> However, permenant magnets are expensive, and slip rings share some of
> the same inefficiencies as DC (although they can do regen more easily
> and are more efficient).

The slip rings in a slip-ring motor don't actually do commutation and only deal with rotor current They can get away with a much harder brush with a higher silver content and the rings are smooth. The point is that you can vary the resistance and excess rotor energy in high slip situations is handled outside the rotor and can even be regenerated back onto the line during motoring operation. Variable frequency drives and the smarts of the dsp control have allowed the standard squirl-cage ACIM to cover enough applications to just about kill the market for slip-ring motors. They still are popular for applications with high inertial starting loads like rock crushers, elevators and some other large applications where they must start under load without pulling excessive amps and/or melting down the rotor.

I think that special ability to accelerate a high inertial load would makes this particular type of ac motor like a dc motor off the line.

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Re: [EVDL] Overdiven 10hp AC

Peter Gabrielsson wrote:
> The AC-150 motor is in fact air cooled, if that's what you were referring to.

Ah, I had missed that! Thanks for the correction.

In that case, I can't explain the difference. Electric motors have a
certain horsepower per pound. It isn't really affected by AC vs. DC, but
rather the basic physics involved. Assuming you're using the same copper
wire, iron laminations, bearings, magnets, etc. then either an AC or DC
motor will have the same performance characteristics

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Re: [EVDL] Overdiven 10hp AC

Hi Lee,

You state some valid points I agree with and a few
where I disagree.

--- Lee Hart <[email protected]> wrote:
<snip>
> A brush has a
> 1-2 volt drop; the IGBTs used in most inverters have
> a 2-3 volt drop, and so are actually somewhat *less*
> efficient.

At high currents, the brush drop can be much higher.
And, as to the efficiency comparison to the solid
state commutation, you neglect the mechanical losses
associated with the brush.

<snip>
> By the time they get done, not one single piece is
> the same as a stock AC motor. Now you have a
> hand-made motor, custom produced in very low
> quantities. No wonder it is expensive!

This thread originally concerned the modified Lincoln
motor. It is, in fact, mostly the same as a "stock"
inverter duty AC motor. Just a winding pattern
change, precision bearings and a coolant system.

Regards,

Jeff M


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Re: [EVDL] Overdiven 10hp AC

Hi Jeff,

You seem to propagate a common misconception here
about poles and torque. It is my opinion that pole
count increase does not increase torque density in
these double air gap motors. Torque is a function of
the total air gap area, flux density and current
density.

Let's stick with 60 Hz induction motors. If you have
a 5 hp rated 4 pole motor, it has a speed of 1800 RPM.
Let's neglect slip for simplicity. So it would have
a rated torque of 14.6 lb.ft. And a 5 hp rated 8 pole
motor would be 900 RPM and have a rated torque of 29.2
lb.ft. It would appear that doubling the pole count
has doubled the torque. Right?

But take a look at a major motor manufacturer's
catalog. The 5 hp, 4 pole motor is a 213 frame size,
115 lbs. The 5 hp, 8 pole motor is a 256 frame size,
211 lbs. Both TENV. The mass has nearly doubled for
twice the torque. The torque density is about the
same.

I'm sure you can find some examples which contradict
this example. Nameplate ratings can be dangerous.
So, with particular cooling schemes, the power ratings
for motors with different pole counts may be in the
same frame size. This is due to the fact that the
rating is strictly dependent on the losses. So if the
motors are of equal efficiency, the power rating will
be the same. But the breakdown torque will also be
the same. You haven't increased the torque with more
poles, you're just rating it at a lower speed.

Regards,

Jeff M

--- Jeff Shanab <[email protected]> wrote:

> This can only apply if you start with a good 10hp AC
> motor to begin
> with. Let me try and explain.
>
> While all motors are a balance between the power you
> put in and the heat
> you can dissipate, the less heat you generate, the
> more you can push this.
> In a dc motor the majority is resistive losses in an
> AC motor the
> reactive losses are a big concern.
>
>
> A little theory:
> The fundamental rpm of an AC motor is 3600/ (# of
> pole pairs) - slip so
> a 4 pole AC Syncronous* motor motor at 60 Hz
> (3600cycles/minute) is 1800 rpm
>
> *Induction Ac motors have slip a percentage the
> rotor lags behind that
> creates the magnetic field needed for torque
> production. This is why you
> see 1725rpm.
>
> The more poles, the more torque at the expense of
> rpm. So a motor that
> is designed for 60hz is huge for it's torque. A
> typical 30hp 60hz motor
> is 18" around by 20" long and weights 100's of
> pounds. But it can be
> made with unsophisticated materials because 60hz is
> such a low
> frequency, that the reactive losses are low. Now
> take the traditional 4
> pole motor and turn it into a 12 pole motor, same
> amount of windings and
> iron and the torque triples, but 600rpm and you
> can't drive very fast.
> The solution is simple, crank the frequency up and
> gear down the result.
> Now a 100lb 10" diameter motor 10" long can do the
> deed. The issue
> becomes the added heat generated as the ac field in
> the laminations
> changes polarity more times per second, the cheap
> laminations don't like
> changing magnetic polarity and resist giving off
> heat. The currents are
> stronger and the cheap oxidation layer between the
> laminations is
> insuffient to stop eddy currents from spiraling
> between laminations
> forming even more loss. The windings vibrate more
> and self destruct in
> less time.



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Re: [EVDL] Overdiven 10hp AC

>
> Hi Jeff,
>
> You seem to propagate a common misconception here
>
I am not propagating any misconceptions here.
> about poles and torque. It is my opinion that pole
> count increase does not increase torque density in
> these double air gap motors. Torque is a function of
> the total air gap area, flux density and current
> density.
>
For a given motor that can run as 4 or 8 pole you are agreeing that the
rpm drops in half with double the poles
And I think you also agree that hp = (rpm*torque)/5252
So the mathematics of this tend to show that if two motors have the same
HP, the product of the rpm and the torque must be the same.
1/2 the rpm means twice the torque.
> Let's stick with 60 Hz induction motors. If you have
> a 5 hp rated 4 pole motor, it has a speed of 1800 RPM.
> Let's neglect slip for simplicity. So it would have
> a rated torque of 14.6 lb.ft. And a 5 hp rated 8 pole
> motor would be 900 RPM and have a rated torque of 29.2
> lb.ft. It would appear that doubling the pole count
> has doubled the torque. Right?
>
OK, you do agree.
> But take a look at a major motor manufacturer's
> catalog. The 5 hp, 4 pole motor is a 213 frame size,
> 115 lbs. The 5 hp, 8 pole motor is a 256 frame size,
> 211 lbs. Both TENV. The mass has nearly doubled for
> twice the torque. The torque density is about the
> same.
>
I wasn't talking about density and I assume what is going on here is
that the 4 pole can get by with lighter construction because it is not
made for the torque.
for example, a Nema 213 has a 1.125 or 1.375 and a 256 has a 1.375 to
1.625 (U or T designation)
> I'm sure you can find some examples which contradict
> this example.
A lot I am afraid, as the primary equation determines this
But i think we can think it through also. common sense

ok, for a given pole pair they each apply a tug on the rotor 120 times a
second at 60hz, once for the positive swing of the arc and once for the
negative.
Sure the size of the poles makes a difference, but I am talking about
the given volume of motor. it still produces the same HP
but instead of energizing 1 pole pair, now we energize a second pair in
parallel, the torque doubles but the rotor now takes 2 cycles to turn a
revolution

> Nameplate ratings can be dangerous.
> So, with particular cooling schemes, the power ratings
> for motors with different pole counts may be in the
> same frame size. This is due to the fact that the
> rating is strictly dependent on the losses.
And here is the point, if it is a wound rotor motor, the excess energy
(that would result in the heat that limits the amount of amps you can
put in for the amount of cooling you have), is brought out of the rotor.
> So if the
> motors are of equal efficiency, the power rating will
> be the same.
Power the same agreed.
> But the breakdown torque will also be
> the same. You haven't increased the torque with more
> poles, you're just rating it at a lower speed.
>
Sorry, I disagree. I could run a math proof, but I promised myself when
I graduated i wouldn't do any more of those.
> Regards,
>
> Jeff M

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Re: [EVDL] Overdiven 10hp AC

Jeff Shanab wrote:

>> But the breakdown torque will also be
>> the same. You haven't increased the torque with more
>> poles, you're just rating it at a lower speed.
>>
> Sorry, I disagree. I could run a math proof, but I promised myself when
> I graduated i wouldn't do any more of those.
>> Regards,
>>
>> Jeff M

Guys, it's obvious. Each poles have so much magnetic
force attracting metal parts, so 8 poles have twice
as much *combined* force than 4 poles, think "teamwork".
Each pole's force is still the same (function of current), but
now you got twice as many, each doing the same job. So torque
on the shaft is doubled with doubling amount of poles. And, indeed twice
the torque by half the speed = same power, no debate there.

Victor

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Re: [EVDL] Overdiven 10hp AC

Personally, I think it's only a matter of test conditions.

ACP's motor is (realistically) not 50kW continuous.
It is mathematically 50 kW just because it spins fast.
It will indeed output 50 kW continuously as long as you
can keep up cooling it, but no reasonable air blower
can dissipate so much heat. Or, motor is continuously
red hot and just can tolerate that. Or the motor
is OK but the intake air must be -40'C.

To compare:

Twice as heavy Siemens 5135WS14 motors have similar torque, but rated
just 45kW continuous at 3500 PRM. Why? If they would choose to rate
them at 8000 RPM (as ACP's) with the same torque, *continuous* power
sure would
be over 90 kW as long as it is being cooled off well enough.
But that's the issue, it can't be cooled with realistic water
flow rate and water temp. Water will just vaporize. 45kW is real
life number with quite high water temp already.

I wish ACP would publish how efficient motor itself is
at 8k RPM and 50 kW continuous output, what is its
temperature, air intake temp, and other test conditions.

Victor

Lee Hart wrote:
> Peter Gabrielsson wrote:
>> The AC-150 motor is in fact air cooled, if that's what you were referring to.
>
> Ah, I had missed that! Thanks for the correction.
>
> In that case, I can't explain the difference. Electric motors have a
> certain horsepower per pound. It isn't really affected by AC vs. DC, but
> rather the basic physics involved. Assuming you're using the same copper
> wire, iron laminations, bearings, magnets, etc. then either an AC or DC
> motor will have the same performance characteristics
>

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Re: [EVDL] Overdiven 10hp AC

Hi Victor,

I have a few comments inserted. And, would you
contact me off list? I have sent product inquires to
you and never get a reply. Thanks.

--- Victor Tikhonov <[email protected]> wrote:

> Personally, I think it's only a matter of test
> conditions.
>
> ACP's motor is (realistically) not 50kW continuous.
> It is mathematically 50 kW just because it spins
> fast.

What difference does it make how fast it spins?
Higher speed, more gear reduction.

I am not sure where the 50 kW rating for AC-150 came
from. I have never seen this spec until this list.

> It will indeed output 50 kW continuously as long as
> you
> can keep up cooling it, but no reasonable air blower
> can dissipate so much heat. Or, motor is
> continuously
> red hot and just can tolerate that. Or the motor
> is OK but the intake air must be -40'C.

Yeah, we used to compete against cars running AC-150
systems. They would load dry ice into the air ducts.

>
> To compare:
>
> Twice as heavy Siemens 5135WS14 motors have similar
> torque, but rated
> just 45kW continuous at 3500 PRM. Why? If they would
> choose to rate
> them at 8000 RPM (as ACP's) with the same torque,
> *continuous* power
> sure would
> be over 90 kW as long as it is being cooled off well
> enough.
> But that's the issue, it can't be cooled with
> realistic water
> flow rate and water temp. Water will just vaporize.
> 45kW is real
> life number with quite high water temp already.
>
> I wish ACP would publish how efficient motor itself
> is
> at 8k RPM and 50 kW continuous output, what is its
> temperature, air intake temp, and other test
> conditions.

>From the ACP web site.

http://www.acpropulsion.com/technology/ac150_efficiency.gif


Looks like 91 percent at 50 kW, 8000 RPM, combined
motor and inverter. But no info on conditions or
thermal tests or ratings.

Regards,

Jeff M

>
> Victor
>
> Lee Hart wrote:
> > Peter Gabrielsson wrote:
> >> The AC-150 motor is in fact air cooled, if that's
> what you were referring to.
> >
> > Ah, I had missed that! Thanks for the correction.
> >
> > In that case, I can't explain the difference.
> Electric motors have a
> > certain horsepower per pound. It isn't really
> affected by AC vs. DC, but
> > rather the basic physics involved. Assuming you're
> using the same copper
> > wire, iron laminations, bearings, magnets, etc.
> then either an AC or DC
> > motor will have the same performance
> characteristics
> >




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Re: [EVDL] Overdiven 10hp AC

--- Victor Tikhonov <[email protected]> wrote:

> Jeff Shanab wrote:
>
> >> But the breakdown torque will also be
> >> the same. You haven't increased the torque with
> more
> >> poles, you're just rating it at a lower speed.
> >>
> > Sorry, I disagree. I could run a math proof, but I
> promised myself when
> > I graduated i wouldn't do any more of those.
> >> Regards,
> >>
> >> Jeff M
>
> Guys, it's obvious. Each poles have so much magnetic
> force attracting metal parts, so 8 poles have twice
> as much *combined* force than 4 poles, think
> "teamwork".
> Each pole's force is still the same (function of
> current), but
> now you got twice as many, each doing the same job.
> So torque
> on the shaft is doubled with doubling amount of
> poles. And, indeed twice
> the torque by half the speed = same power, no debate
> there.
>
> Victor

Hi Victor,

You say each pole's force is the same. So that infers
each pole is the same size. Then doubling the number
of poles doubles the total air gap area. And you have
twice as big a motor for twice the torque. And half
the speed at the same frequency, so the same power for
each.

Regards,

Jeff M



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Re: [EVDL] Overdiven 10hp AC

Hi Jeff,

>From your original post: "Now take the traditional 4
pole motor and turn it into a 12 pole motor, same
amount of windings and iron and the torque triples".

That sounded like you were talking torque density to
me. Sorry if I misunderstood you.

Regards,

Jeff M

--- Jeff Shanab <[email protected]> wrote:

<snip>
> I wasn't talking about density
<snip>



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Re: [EVDL] Overdiven 10hp AC

hey guys these motors are used on cnc machines that are high speed and they NEED A BUNCH of cooling those that have access to milling / drilling machine check it out and the mystery will go away
----- Original Message -----
From: Jeff Major<mailto:[email protected]>
To: Electric Vehicle Discussion List<mailto:[email protected]>
Sent: Wednesday, October 03, 2007 9:26 AM
Subject: Re: [EVDL] Overdiven 10hp AC



Hi Jeff,

>From your original post: "Now take the traditional 4
pole motor and turn it into a 12 pole motor, same
amount of windings and iron and the torque triples".

That sounded like you were talking torque density to
me. Sorry if I misunderstood you.

Regards,

Jeff M

--- Jeff Shanab <[email protected]<mailto:[email protected]>> wrote:

<snip>
> I wasn't talking about density
<snip>



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