# Copper in a 350 HP motor

Discussion in 'General Electronics Chat' started by tbeaver, Nov 1, 2009.

1. ### tbeaver Thread Starter New Member

Oct 4, 2009
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Would anyone care to guess ( or if you know) about how much copper would be in a 350 horse power, 3 phase, 3100 pound motor? Even a ruff guess would be better then i have now. Thanks in advance.

2. ### steveb Senior Member

Jul 3, 2008
2,433
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Do you have access to the motor? If so, you can measure the phase resistance with an Ohm-meter. This measurement goes a long way in estimating the copper in the phase windings. In particular, with this measurement, you restrict the wire-gauge/wire length combinations that are possible. One can then estimate the wire gauge from the current level, which is estimated from the known power and voltage. Once you know wire gauge and wire length per phase, estimating the amount of copper is easy since the conductivity of copper is known. It is also helpful to provide some details of the motor type and dimensions of the motor, rotor and coils, since estimates of coil volume also help refine the estimate of copper weight, since the density of copper is known.

Note that large motors often have small values of phase resistance (< 1 Ohm), so be sure that the measurement technique is accurate.

3. ### ifixit Distinguished Member

Nov 20, 2008
639
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I have a 1HP, 1PH, open frame motor & it looks like about 1/4 of the weight would be copper. Therefore scaling up to a 350HP motor would be 0.25 X 3100lbs = 775lbs... I guess.

775 X \$3/lb = \$2,325.oo

Jul 7, 2009
1,585
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I'd guess your best estimate might come from contacting a place that works on and rewinds motors. Lots of them to choose from in the phone book (assuming you're near a reasonably large city).

5. ### Andrew Leigh Well-Known Member

Sep 8, 2008
92
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Hi,

400lbs is the average weight (2, 4 or 6 pole). It is not proportion to the mass of the frame.

Cheers
Andrew

6. ### tbeaver Thread Starter New Member

Oct 4, 2009
6
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Thanks guys. even a estimate of 400 to 775 helps. So i'll assume that a 270 HP older motor is going to be the same then?

7. ### Andrew Leigh Well-Known Member

Sep 8, 2008
92
2
Hi,

this info come from a motor rewinding friend of mine. It will be less.

Cheers
Andrew