Al Magnet Wire Motors

[Bret Cahill]

Now that my utility is calling Cu a "precious metal" in its anti-wire
theft campaign what is the status of Al wound motor development?

Supposedly the WWII era Al motors burned up easily but there shouldn't
be any reason why they couldn't be protected very cheaply nowdays.

If a motor costs several cents/watt and develops 1 W/gm a motor and
the cost of copper is 1 cent/gm maybe a third of the cost is copper.


Bret Cahill

 

[Bret Cahill]

Now that my utility is calling Cu a "precious metal" in its anti-wire
theft campaign what is the status of Al wound motor development?

Supposedly the WWII era Al motors burned up easily but there shouldn't
be any reason why they couldn't be protected very cheaply nowdays.

If a motor costs several cents/watt and develops 1 W/gm a motor and
the cost of copper is 1 cent/gm maybe a third of the cost is copper.

One reason is no one is going to give up even a little of the 95%
efficiency of Cu windings for just one cent/watt, the cost advantage
of Al.


Bret Cahill

 

[Dean Hoffman]

Bret Cahill wrote:

Now that my utility is calling Cu a "precious metal" in its anti-wire
theft campaign what is the status of Al wound motor development?

Supposedly the WWII era Al motors burned up easily but there shouldn't
be any reason why they couldn't be protected very cheaply nowdays.

If a motor costs several cents/watt and develops 1 W/gm a motor and
the cost of copper is 1 cent/gm maybe a third of the cost is copper.


Bret Cahill

Aluminum wire requires different connectors than copper. It
expands and contracts more with temperature changes. Check with the EEs
over at alt.engineering.electrical. They could give you a definitive
answer.


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[Bret Cahill]

On Oct 29, 7:53�am, Bret Cahill <BretCah...@aol.com> wrote:

Now that my utility is calling Cu a "precious metal" in its anti-wire
theft campaign what is the status of Al wound motor development?

Supposedly the WWII era Al motors burned up easily but there shouldn't
be any reason why they couldn't be protected very cheaply nowdays.

If a motor costs several cents/watt and develops 1 W/gm a motor and
the cost of copper is 1 cent/gm maybe a third of the cost is copper.

One reason is no one is going to give up even a little of the 95%
efficiency of Cu windings for just one cent/watt, the cost advantage
of Al.

Figure the cost of the electricity is an order of magnitude greater
than the cost of the motor, maybe 30X more than the copper at current
prices and even a 1% decrease in efficiency isn't worth the capital
cost savings.

Al will probably never be more cost effective.


Bret Cahill

 

Now that my utility is calling Cu a "precious metal" in its anti-wire
theft campaign what is the status of Al wound motor development?

Supposedly the WWII era Al motors burned up easily but there shouldn't
be any reason why they couldn't be protected very cheaply nowdays.

If a motor costs several cents/watt and develops 1 W/gm a motor and
the cost of copper is 1 cent/gm maybe a third of the cost is copper.

Bret Cahill

� � �Aluminum wire requires different connectors than copper. �It
expands and contracts more with temperature changes. ďż˝

Al also melts a much lower temperature but these issues might all be
resolved with proper design and controls.

At least one killer is the conductivity of Al is 30% less than Cu
which means the coils in an aluminum motor wouldn't pack as tight for
the same current & field and the motor wouldn't be as efficient as
copper. Since the cost of electricity over the lifetime of a motor
might be an order of magnitude more than the motor itself, the 30%
increase in capital cost of a Cu motor over Al can be justified with
only a 1 or 2% efficiency increase.

Copper probably can provide that efficiency increase.

Check with the EEs
over at alt.engineering.electrical. ďż˝ They could give you a definitive
answer.

OK.

I'll also ask about those "pegleg" transmission line towers that have
one wood pole leg and one steel with a wood pole running across the
top.


Bret Cahill

 

[Mark Thorson]

BretCahill@peoplepc.com wrote:

At least one killer is the conductivity of Al is 30% less than Cu
which means the coils in an aluminum motor wouldn't pack as tight for
the same current & field and the motor wouldn't be as efficient as
copper. Since the cost of electricity over the lifetime of a motor
might be an order of magnitude more than the motor itself, the 30%
increase in capital cost of a Cu motor over Al can be justified with
only a 1 or 2% efficiency increase.

Perhaps silver could be justified in this application.

 

At least one killer is the conductivity of Al is 30% less than Cu
which means the coils in an aluminum motor wouldn't pack as tight for
the same current & field and the motor wouldn't be as efficient as
copper. �Since the cost of electricity over the lifetime of a motor
might be an order of magnitude more than the motor itself, the 30%
increase in capital cost of a Cu motor over Al can be justified with
only a 1 or 2% efficiency increase.

Perhaps silver could be justified in this application.

What application? Swindling the ignorant?

A 5% increase in conductivity won't result in anywhere near a 5%
efficiency increase, certainly not enough to make up for an order of
magnitude or so higher capital cost.

Maybe there is some really coincidencial situation where the only
motor that will work must be slightly smaller that what is possible
with Cu.

But that's a small market.


Bret Cahill

 

[Don Kelly]

----------------------------
<BretCahill@peoplepc.com> wrote in message
news:2c6f0238-16e4-4d32-8f0f-11f4610e7fe7@o40g2000prn.googlegroups.com...

Now that my utility is calling Cu a "precious metal" in its anti-wire
theft campaign what is the status of Al wound motor development?

Supposedly the WWII era Al motors burned up easily but there shouldn't
be any reason why they couldn't be protected very cheaply nowdays.

If a motor costs several cents/watt and develops 1 W/gm a motor and
the cost of copper is 1 cent/gm maybe a third of the cost is copper.

Bret Cahill

? ? ?Aluminum wire requires different connectors than copper. ?It
expands and contracts more with temperature changes. ?

Al also melts a much lower temperature but these issues might all be
resolved with proper design and controls.

At least one killer is the conductivity of Al is 30% less than Cu
which means the coils in an aluminum motor wouldn't pack as tight for
the same current & field and the motor wouldn't be as efficient as
copper. Since the cost of electricity over the lifetime of a motor
might be an order of magnitude more than the motor itself, the 30%
increase in capital cost of a Cu motor over Al can be justified with
only a 1 or 2% efficiency increase.

Copper probably can provide that efficiency increase.

Check with the EEs
over at alt.engineering.electrical. ? They could give you a definitive
answer.

OK.

I'll also ask about those "pegleg" transmission line towers that have
one wood pole leg and one steel with a wood pole running across the
top.


Bret Cahill

Using aluminum, larger conductors to keep the same resistance means that the
motor becomes larger. This affects core losses and to counter that means
more turns. In addition, the motor would have to run a bit cooler -this
also adds to the size problem.
It all comes down to a balance between the performance (including
efficiency) and costs. going to aluminum may be OK in some cases but the
overall savings may not be there. It would require a hard nosed analysis of
all the factors. I expect that manufacturers have already explored this
option considering today's copper prices.

With transmission lines it is easier- wrap the aluminum around a steel core
and go with it- this was recognized in the late 1930's.

I've not seen the "pegleg" construction but I suspect that either the steel
tower or the wood tower was there earlier and it was the cheapest
alternative when upgrading transmission capacity to simply add the other
tower and the crossbar to get the needed spacing between phases at a higher
voltage.
--

Don Kelly dhky@shawcross.ca
remove the X to answer

 

[Bret Cahill]

Now that my utility is calling Cu a "precious metal" in its anti-wire
theft campaign what is the status of Al wound motor development?

Supposedly the WWII era Al motors burned up easily but there shouldn't
be any reason why they couldn't be protected very cheaply nowdays.

If a motor costs several cents/watt and develops 1 W/gm a motor and
the cost of copper is 1 cent/gm maybe a third of the cost is copper.

Bret Cahill

? ? ?Aluminum wire requires different connectors than copper. ?It
expands and contracts more with temperature changes. ?

Al also melts a much lower temperature but these issues might all be
resolved with proper design and controls.

At least one killer is the conductivity of Al is 30% less than Cu
which means the coils in an aluminum motor wouldn't pack as tight for
the same current & field and the motor wouldn't be as efficient as
copper. �Since the cost of electricity over the lifetime of a motor
might be an order of magnitude more than the motor itself, the 30%
increase in capital cost of a Cu motor over Al can be justified with
only a 1 or 2% efficiency increase.

Copper probably can provide that efficiency increase.

Check with the EEs
over at alt.engineering.electrical. ? They could give you a definitive
answer.

OK.

I'll also ask about those "pegleg" transmission line towers that have
one wood pole leg and one steel with a wood pole running across the
top.

Bret Cahill

Using aluminum, larger conductors to keep the same resistance means that the
motor becomes larger. This affects core losses and to counter that means
more turns. �In addition, the motor would have to run a bit cooler -this
also adds to the size problem.

It might not even be lighter than a Cu motor, Al's only major selling
point besides being a somewhat less desirable target for thieves.

�It all comes down to a balance between the performance (including
efficiency) �and costs.

If the cost of electricity went way down then Al might make sense.

going to aluminum may be OK in some cases but the
overall savings may not be there. It would require a hard nosed analysis of
all the factors. I expect that manufacturers have already explored this
option considering today's copper prices.

If it were close they would be fine tuning their spreadsheets.

With transmission lines it is easier- wrap the aluminum around a steel core
and go with it- this was recognized in the late 1930's.

I've not seen the "pegleg" construction but I suspect that either the �steel
tower or the wood tower �was there earlier and it was the cheapest
alternative when upgrading transmission capacity to simply add the other
tower and the crossbar to get the needed spacing between phases at a higher
voltage.

Sounds plausible. No one here would waste much time sourcing a
matching pole just for aesthetics. Add the cheapest support and call
it a day.

Maybe they could save some ground wire with the metal poles.


Bret Cahill

 

[Robert Copcutt]

Bret Cahill wrote:

Now that my utility is calling Cu a "precious metal" in its anti-wire
theft campaign what is the status of Al wound motor development?

Supposedly the WWII era Al motors burned up easily but there shouldn't
be any reason why they couldn't be protected very cheaply nowdays.

If a motor costs several cents/watt and develops 1 W/gm a motor and
the cost of copper is 1 cent/gm maybe a third of the cost is copper.


Bret Cahill

The resistivity of copper at 20C is 1.673 microhm-cm and its density is
8.96 g/cm3. Therefore if the cross section area of a copper wire is
1.673cm2 it will have a resistance of 1 microhm/cm and the mass will be
1.673 x 8.96 = 15.0g/cm.

The resistivity of aluminium at 20C is 2.655 microhm-cm and its density
is 2.70 g/cm3. Therefore if the cross section area of an Al wire is
2.655cm2 it will have a resistance of 1 microhm/cm and its mass will be
2.655 x 2.70 = 7.17g/cm.

It is therefore clear that Al is a far better conductor on a mass basis.
Connection is a problem but I was recently reading about a company that
claims to have broken all power to weight ratio records with an Al
motor. Each coil was a 3/4 turn and built up of 4 custom shaped rods of
aluminium. Two of the rods where shaped to exactly fit into the holes in
the magnetic laminations. These rods had threaded holes in both ends.
The other 2 rods were screwed to the first two rods to connect them
together on one side and to the neighbouring coils on the other side.

Sorry but I cannot find the link at the moment.

 

[zzbunker@netscape.net]

On Oct 28, 1:08 pm, Bret Cahill <BretCah...@aol.com> wrote:

Now that my utility is calling Cu a "precious metal" in its anti-wire
theft campaign what is the status of Al wound motor development?

Well, none actually. The only thing that's been done with motors
of any kind in the last 50 years is making A.I., Robots, Fiber
Optics,
and Digital Motor Controllers. Since that not only reduces the
motor cost,
it's get rid of the wiire theft problem too.

Supposedly the WWII era Al motors burned up easily but there shouldn't
be any reason why they couldn't be protected very cheaply nowdays.

If a motor costs several cents/watt and develops 1 W/gm a motor and
the cost of copper is 1 cent/gm maybe a third of the cost is copper.

Bret Cahill

 

[Bret Cahill]

Now that my utility is calling Cu a "precious metal" in its anti-wire
theft campaign what is the status of Al wound motor development?

Supposedly the WWII era Al motors burned up easily but there shouldn't
be any reason why they couldn't be protected very cheaply nowdays.

If a motor costs several cents/watt and develops 1 W/gm a motor and
the cost of copper is 1 cent/gm maybe a third of the cost is copper.

Bret Cahill

The resistivity of copper at 20C is 1.673 microhm-cm and its density is
ďż˝ 8.96 g/cm3. Therefore if the cross section area of a copper wire is
1.673cm2 it will have a resistance of 1 microhm/cm and the mass will be
1.673 x 8.96 = 15.0g/cm.

The resistivity of aluminium at 20C is 2.655 microhm-cm and its density
is �2.70 g/cm3. Therefore if the cross section area of an Al wire is
2.655cm2 it will have a resistance of 1 microhm/cm and its mass will be
2.655 x 2.70 = 7.17g/cm.

It is therefore clear that Al is a far better conductor on a mass basis.

That doesn't necessarily mean a lighter motor. The efficiency might
drop a lot.

Connection is a problem but I was recently reading about a company that
claims to have broken all power to weight ratio records with an Al
motor.

Maybe there is a future for electric airships.

Each coil was a 3/4 turn and built up of 4 custom shaped rods of
aluminium. Two of the rods where shaped to exactly fit into the holes in
the magnetic laminations. These rods had threaded holes in both ends.
The other 2 rods were screwed to the first two rods to connect them
together on one side and to the neighbouring coils on the other side.

Sorry but I cannot find the link at the moment.

Someone else will.


Bret Cahill

 

[Robert Copcutt]

The resistivity of copper at 20C is 1.673 microhm-cm and its density is
ďż˝ 8.96 g/cm3. Therefore if the cross section area of a copper wire is
1.673cm2 it will have a resistance of 1 microhm/cm and the mass will be
1.673 x 8.96 = 15.0g/cm.

The resistivity of aluminium at 20C is 2.655 microhm-cm and its density
is �2.70 g/cm3. Therefore if the cross section area of an Al wire is
2.655cm2 it will have a resistance of 1 microhm/cm and its mass will be
2.655 x 2.70 = 7.17g/cm.

It is therefore clear that Al is a far better conductor on a mass basis.

That doesn't necessarily mean a lighter motor. The efficiency might
drop a lot.

Where do the efficiency losses come from? The IR losses in the wire
dominate. In the example above I made the wire resistance the same in
both cases.

The next biggest loss comes from eddy currents in the magnetic material.
Why should there be a difference between an Al and a Cu motor? The
magnetic field will have to travel a bit further in the Al motor but
spinning a little faster will make up for that difference.

Connection is a problem but I was recently reading about a company that
claims to have broken all power to weight ratio records with an Al
motor.

Maybe there is a future for electric airships.

Of course there is. Electric motors already dominate the radio
controlled aircraft business. That was probably where I read about the
Al motor.

 

[Bret Cahill]

Maybe there is a future for electric airships.

Of course there is. Electric motors already dominate the radio
controlled aircraft business.

That's not transcontinental transportation but that's not necessarily
an argument against all long range turbineless flight either.

Just last week they announced that they discovered a bird that flies
7,000 miles nonstop, the world record for the animal kingdom. Maybe
it eats flying bugs on the way but it's still amazing. If a bird can
do it . . .

A bird might have to go 40 - 60 knots/hour to get its Reynolds number
up to the magic 80,000 -- 100,000 where the drag coefficient drops
precipitously. Some birds' feathers must act like dimples on a golf
ball.

Have they tried dimples on radio controlled aircraft? The size and
speed could designed around N re = 100,000 and dimpling could vastly
extent the range of such craft.

Widebodies reach Nre = 100,000 going 0.1 knots so dimples won't work
there.

That was probably where I read about the
Al motor.

If you could get the specific power up to 5 - 7 kW/kg even sacrificing
some efficiency might be acceptable.


Bret Cahill

 

[John Fields]

On Tue, 4 Nov 2008 10:41:52 -0800 (PST), Bret Cahill
<BretCahill@aol.com> wrote:

A bird might have to go 40 - 60 knots/hour

---
It's not "knots/hour", it's just "knots".

JF

 

On Oct 29, 5:08 am, Bret Cahill <BretCah...@aol.com> wrote:

Now that my utility is calling Cu a "precious metal" in its anti-wire
theft campaign what is the status of Al wound motor development?

Supposedly the WWII era Al motors burned up easily but there shouldn't
be any reason why they couldn't be protected very cheaply nowdays.

If a motor costs several cents/watt and develops 1 W/gm a motor and
the cost of copper is 1 cent/gm maybe a third of the cost is copper.

Bret Cahill

Aluminum is used in the cast rotors of squirrel cage induction motors
to replace copper where cost is more important than efficiency or
where the higher resistance of aluminum is indeed more important.

What would concern me the most about aluminum is its apparent tendency
to fatigue quicker than copper.

Copper prices have dropped to 40% of their value 2 months ago due to
the world credit crisis.

 

Now that my utility is calling Cu a "precious metal" in its anti-wire
theft campaign what is the status of Al wound motor development?

Supposedly the WWII era Al motors burned up easily but there shouldn't
be any reason why they couldn't be protected very cheaply nowdays.

If a motor costs several cents/watt and develops 1 W/gm a motor and
the cost of copper is 1 cent/gm maybe a third of the cost is copper.

Bret Cahill

Aluminum is used in the cast rotors of squirrel cage induction motors
to replace copper where cost is more important than efficiency or
where the higher resistance of aluminum is indeed more important.

What would concern me the most about aluminum is its apparent tendency
to fatigue quicker than copper.

So there is always _some_ flexing or movement of magnet wire no matter
how tightly wound?

Al has no fatigue limit. Sooner or later, with enough cycling, it
will crack.

Steel would be even cheaper and the strains could be designed under
its fatigue limit. It could then cycle forever without breaking.

Does copper have a fatigue limit?

Copper prices have dropped to 40% of their value 2 months ago due to
the world credit crisis.

Same if not a bigger drop for Al.


Bret Cahill

 

[Rich Grise]

On Tue, 04 Nov 2008 16:02:06 -0600, John Fields wrote:

On Tue, 4 Nov 2008 10:41:52 -0800 (PST), Bret Cahill <BretCahill@aol.com

A bird might have to go 40 - 60 knots/hour

It's not "knots/hour", it's just "knots".

Maybe he was talking about acceleration. ;-)

Cheers!
Rich

 

On Nov 6, 4:05 am, BretCah...@peoplepc.com wrote:

Now that my utility is calling Cu a "precious metal" in its anti-wire
theft campaign what is the status of Al wound motor development?

Supposedly the WWII era Al motors burned up easily but there shouldn't
be any reason why they couldn't be protected very cheaply nowdays.

If a motor costs several cents/watt and develops 1 W/gm a motor and
the cost of copper is 1 cent/gm maybe a third of the cost is copper.

Bret Cahill

Aluminum is used in the cast rotors of squirrel cage induction motors
to replace copper where cost is more important than efficiency or
where the higher resistance of aluminum is indeed more important.
What would concern me the most about aluminum is its apparent tendency
to fatigue quicker than copper.

So there is always _some_ flexing or movement of magnet wire no matter
how tightly wound?

There are physical stresses on the coil due to the magnetic forces.

Al has no fatigue limit.  Sooner or later, with enough cycling, it
will crack.

I presume you meant it HAS a fatique limit.

Steel would be even cheaper and the strains could be designed under
its fatigue limit.  It could then cycle forever without breaking.

Unfortunately its conductivity is vastly lower; it is however common
to include steel wire in the multistrand core of overhead transmission
lines. Motors are however wound with single strand wire.

I understand what you mean about the lack of fatigue limit. It would
no doubt be possible to make a steel wired motor as well as an
aluminum unit. The question is: what will happen to the wieght, size,
cost and efficiency of such a motor?

Does copper have a fatigue limit?

all metals do bar steel I think. Copper has greater malleability and
ductility. Consider the case of copper wiring for housing which once
had a reputation for starting fires (presumably becuase installation
procedures hadn't been followed or developed). It can be pulled
around tight bends and can be clamped into a crude and rather nasty
screw terminal without wire protection. Aluminum can cause house
fires if treated similarly. At the bare minimum the wire terminal
needs protection from the screw (by a flat) and in reality should be
ferruled within a corrosion protection paste or grease. I might add
that the lastest Airbus A380 transmits its power electrically using
aluminium wiring instead of hydraulically.

Copper prices have dropped to 40% of their value 2 months ago due to
the world credit crisis.

Same if not a bigger drop for Al.

Bret Cahill

 

[John Fields]

On Fri, 7 Nov 2008 04:31:41 -0800 (PST), eunometic@yahoo.com.au wrote:

I might add
that the lastest Airbus A380 transmits its power electrically using
aluminium wiring instead of hydraulically.

---
Thanks for the info; I'll _never_ fly in an A380.


JF