Author Topic: New revelation in motor selection  (Read 1841 times)

Offline mizlplix

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New revelation in motor selection
« on: July 20, 2014, 06:59:43 AM »
New revelation in motor selection
___________________________________________________________________________ ________________________________________

Hello everyone:

Ivan and I have been talking lately about how good his liquid cooled motor is.
 It is based on a two year old (or there abouts) motor.  It is rewound exactly
the same as my present motor is, but it actually has more torque.......

My motor is based on a 20 HP frame, Ivan's is a 10 HP frame.

My motor was at least 30 Ft/Lbs of torque less.  Why?

After a lengthy discussion, we both came to the same realization that the
smaller motor was more efficient, by at least 30%. Why is that so?  There
can be only one reason....It has better iron laminations......

Twenty years ago, the steel foundrys were still analog.  Their steel alloying
process was to weigh out each additive and just melt them together.

The process is very different today.  Everything is digital.  The ingredients
are carefully monitored as the metal alloy is created. (Giving a more precise
and duplicat-able product.)

After several conversations with a large motor builder/rebuilder in North Carolina
I came away with a whole new impression of that industry.

I could actually pick from seven different metal alloys for my stator and rotor laminations.
Oddly enough, the rotor and stator would use different alloys in their construction.

I am now considering ordering new stator laminations for one motor and replacing the stator
with a supposedly better one and then doing some dyno time to compare results.

(A newer motor core might be cheaper)

More later, Miz
1930 Ford Speedster, AC50, full manual powerglide, 6.14gears, 38-130AH CALBs.

Offline few2many

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Re: New revelation in motor selection
« Reply #1 on: August 20, 2014, 09:38:59 PM »
A 20 hp frame is way different in size than a 10 hp frame.  When you say "it is rewound exactly the same as...", how could it be? It may have the same number of turns, coils, and in-hand, but is the total length of wire the same? Maybe the 10 hp uses less wire length, causing it to use higher amps which relates to more torque?
I agree that newer laminations would be more magnetically efficient, have you thought of using the Prius stator?
On second thought, the prius stator is pretty thin, not a lot of iron because the high voltage and it doesnt need to inducr much rotor current.

Offline mizlplix

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Re: New revelation in motor selection
« Reply #2 on: August 20, 2014, 10:18:14 PM »
Exactly the same means exactly the same.  (2 turns/12 in hand)

The stator slot size regulates the wire length.  Since I have not bought the core motor, then
discussing wire length is immaterial.

EXAMPLE: One of the motors had 14 in hand because 12 in hand would have done 3 turns to get slot fill. 
                  OK, by moving up to 15 Ga. wire from 18 Ga would have let us  keep the same 12 in hand,
                  and 2 turns, but it complicates our inventory AND is much harder to wind by hand.

                   15 Ga wire does not lay in the slot as well as 18 does.  It leaves a lot of space between the wires.
                    Air space is to be avoided as it reduces magnetic ability and increases heating from less conduction surface.

With a Curtis controller, two turns is the key to everything.  It keeps the voltage range within what the controller's range.

Miz 

1930 Ford Speedster, AC50, full manual powerglide, 6.14gears, 38-130AH CALBs.

Offline few2many

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Re: New revelation in motor selection
« Reply #3 on: August 20, 2014, 11:16:07 PM »
What was the length of wire in the 10hp, vs the 20hp? Length of wire has an ecffect on voltage and current. If your two turns uses twice the wire length, or any significant amount more, than the 2 turns in the smaller motor, it would change the motor voltage considerably. Maybe the two turns in the 10hp was more in line with the curtis voltage range than the 2 turns in the 20hp.
Basically, what I'm trying to determine, is what reasons other than steel laminations, would cause a motor half the size and rating, to put out 30ft/lbs more torque.

Offline mizlplix

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Re: New revelation in motor selection
« Reply #4 on: August 21, 2014, 03:29:53 AM »
Ivan would need to answer that on the lengths of wire in what motor.

"Basically, what I'm trying to determine, is what reasons other than steel laminations, would cause a motor half the size and rating, to put out 30ft/lbs more torque."

Steel laminations could easily do 30HP.  The coil causes a magnetic field in the stator.  The stator induces a mirror field in the rotor.  The rotor field being out of phase seeks it's like field and rotates.  The rotational effort (torque) is felt in the stator coil as the poles pass causing momentary hard/easy/hard/easy spots.  These hard/easy spots make the current flow/resist/flow/resist.  In effect, meter the current.  This metering effect is regulated by the load on the rotor.  An 8" rotor with the same load rotates in effect, easier than a 5" rotor.  (Leverage)  Which should make the 8" rotor use more current for the same job.  If everything were the same, the smaller rotor should produce less torque than the 8" rotor.  Result= something is different because the torque is not representative.

My guess is that the alloy in the plates is of a better magnetic quality.

Miz
1930 Ford Speedster, AC50, full manual powerglide, 6.14gears, 38-130AH CALBs.