Delay line coil for Newman motor?

[hartiberlin]

Higher voltages and more wire ( more total wire DC resistance) will increase efficiency
while keeping the input power constant.

[kmarinas86]

Results: Not good.

While the voltage was 1/3rd the original setup.
The current went up by about 1.7*3.
Total power in increased by 1.7.
The speed went DOWN 1.7
Residual torque went DOWN as well.
I would say the output fell by 1.7^3 so the efficiency FELL by 9x.

Splitting up the coil and battery pack into parts in a Newman motor: MY BAD IDEA (Not Newman's Idea).

Now I figure it is time to explain these negative results which appeared quite contrary to my explanations.

It appears that the field intensity (telsas) produced in each coil increased by sqrt(3) times. This increased magnetic flux over the course of the rotation by the sqrt(3). The result was a fall in rpm by sqrt(3). Now according to this, the torque driving the motor must have increased by 3 (assuming the motor is operating well below the magnetic saturation point).

This mode of operation seemed completely unnecessary, because with the prior setup I could have instead attached a fan which requires 3 times as much torque to operate at the same lower rpm. Such a larger fan could have done better to convert the otherwise underutilized static (sound) pressure in the rotor system into velocity pressure.

Why did the current increase by sqrt(3)? I do not know how my division of the coil into connecting the three coils in parallel rather than series could lead to this kind of result. What I do know is that there is an increase of the acceleration of current relative to the acceleration of the rotor. This probably has to do with a reduced time L/R constant designated to each coil and its charge flow.

The prior setup is what I still have, and with one final semester of school to complete, I remain hesitant to buy the $200 32" metallic fan blade. I am sure that with the new "vibrating" commutator I have, I will have many small back-emf spikes that can adapt to future fan sizes.

I got it working again in the more efficient setup with only one coil and one pack. 

I guess I have only two choices to further progess: Increase the voltage and increase the fan diameter =P.

The following is still my plan:

__________________________________________________

Below is a plan I made in the last week which I hope to finish in the next month:

I can get a scaled up version of my fan (METAL) for $200 and it is 32" so will do (32/19.375)^5 or 12 times the work per revolution at the same rpm. I predict that the rpm will fall as follows:

(32/19.375)^5/y^2 = (((10/9)y)^2-1^2)/((10/9)^2-1^2)

Solve for y:

((10/9)^2-1^2)*(32/19.375)^5 = y^2(((10/9)y)^2-1^2)
(0.234568)*(32/19.375)^5 = y^2(((10/9)y)^2-1)
2.882771 = y^2(((10/9)y)^2-1)
2.882771 = (10/9)^2y^4-y^2
0 = (10/9)y^4-y^2-2.882771
y^2=1.986
y=1.41

(1-1/1.41) = a 29% drop in rpm relative to 19.375" fan setup

This assumes:
1) Adding the 19.375 inch fan, where there used to be none, drops the rpm by 10%
2) The torque will increase by the square of the current
3) The current will increase inversely to the rpm (assuming that period << inductance/resistance)

(32/19.375)^5/y^2 = Increase in torque = 8.7 times
(32/19.375)^5/y^3 = Increase in power = 6.2 times
(32/19.375)^5/y^4 = Increase in efficiency = 4.4 times
(32/19.375)/y = Increase in fan tip speed = 1.2 times

To get the same efficiency increase by increasing the voltage, I would have to increase voltage by 4.4 times! But at that point, I am likely to be in the regime of magnetic saturation, and to bypass that, I would have to further increase the coils....

The maximum increase in efficiency I can get with this method is:

((10/9)^2-(1/y)^2)/((10/9)^2-1^2) = 5.26

Which increases with larger y.

This is assuming that adding the 19.375" fan blade decreases the rpm by (1-1/(10/9)) or 10%.

[kmarinas86]

I finally bought the 32" metallic fan blade!  ;D

It will ship via UPS ground. I will have it setup maybe in two weeks and post a video on Youtube soon after.

[kmarinas86]

Newman Motor with 32 inch fan blade between 8 to 11 watts
http://www.youtube.com/watch?v=10W7qIxoNUo

144 Volts before load (before machine is turned on)
133 Volts before batteries recover from load (soon after the machine is turned off)

133 Volts / (95 RPM=best case for this voltage) = 1.4 volts per rpm

An earlier setup (19.375" fan blade) ran at 240 RPM with 217 Volts or = 0.9 volts per rpm

1.56x drop in rpm per volt with fan (Prediction was 1.4x)

With half the number of batteries, as shown in the video above, the rpm is cut down to 46RPM.

Below is a plan I made in the last week which I hope to finish in the next month:

I can get a scaled up version of my fan (METAL) for $200 and it is 32" so will do (32/19.375)^5 or 12 times the work per revolution at the same rpm. I predict that the rpm will fall as follows:

(32/19.375)^5/y^2 = (((10/9)y)^2-1^2)/((10/9)^2-1^2)

Solve for y:

((10/9)^2-1^2)*(32/19.375)^5 = y^2(((10/9)y)^2-1^2)
(0.234568)*(32/19.375)^5 = y^2(((10/9)y)^2-1)
2.882771 = y^2(((10/9)y)^2-1)
2.882771 = (10/9)^2y^4-y^2
0 = (10/9)y^4-y^2-2.882771
y^2=1.986
y=1.41

(1-1/1.41) = a 29% drop in rpm relative to 19.375" fan setup

This assumes:
1) Adding the 19.375 inch fan, where there used to be none, drops the rpm by 10%
2) The torque will increase by the square of the current
3) The current will increase inversely to the rpm (assuming that period << inductance/resistance)

(32/19.375)^5/y^2 = Increase in torque = 8.7 times
(32/19.375)^5/y^3 = Increase in power = 6.2 times
(32/19.375)^5/y^4 = Increase in efficiency = 4.4 times
(32/19.375)/y = Increase in fan tip speed = 1.2 times

To get the same efficiency increase by increasing the voltage, I would have to increase voltage by 4.4 times! But at that point, I am likely to be in the regime of magnetic saturation, and to bypass that, I would have to further increase the coils....

The maximum increase in efficiency I can get with this method is:

((10/9)^2-(1/y)^2)/((10/9)^2-1^2) = 5.26

Which increases with larger y.

This is assuming that adding the 19.375" fan blade decreases the rpm by (1-1/(10/9)) or 10%.

[kmarinas86]

A few months ago, I thought that adding the second carbon brush at the switch (the back end of the shaft of my motor) sounded like a good idea for my project.

It turns out however it draws more current (four times as much - with no particular meaning to the 4 factor I think) than I needed to and drains the motor down without improving the torque or rpm. It would draw something like 0.16 amps when 300 volts were used.

With the larger 32" fan, doubling the voltage only increases the rpm from 95RPM to 140RPM.

I have gone back to the commutator where the switch uses a wire connected directly to the battery pack. This did not affect much the rpm per volt, however the current did fall significantly (now back to 0.04 amps). The problem I had with it earlier (i.e. keeping it in position) is no longer an issue with the remedy that I made when I added the second carbon brush.

I know that without a fan at all, the RPM at 300V increases to 370RPM which is peculiar to the new setup. _{For just prior to this the top RPM at 300V was only 300RPM and dropping only 10% with the small fan load - that is, with poor alignment and a very damaged commutator wire).}

With the larger fan, the rpm in the new setup drops by >60%! It appears that as much as the small fan was outgrown by the large motor, the larger fan has easily outgrown the motor as it is. I plan to the clean up the coil sometime in December. A few segments of my middle-level coil (neither the top or bottom) is burnt out (all contiguous and has been that way for the better part of 2009), but thank goodness it is segmented, so I can just remove it and that should help improve the speed again. I may add one or two coils on the top for a total of either 4 or 5 coils. This will surely bring down when no fan is loaded the RPM per volt but I do know that RPM drop will be cut significantly. Perhaps the rpm drop % will be reduced in half (i.e. 30% drop from top rpm).

For four or five coils, I estimate that the RPM will be 160 using 300 volts. The output would be the same as my smaller fan spinning at 369RPM (Calculation = 160RPM*((32"/19.375")^5)^(1/3)). The fastest my smaller fan ever spun was 340 RPM and that is with 2/3rds the voltage. However, that is not accounting for the better flow of air around my much larger fan which extends further out from the motor. It also ignores the possibility that my current can fall significantly as soon as the new changes are made. I hope to see 0.02 amps usage again. Which would mean less power (6 watts only!).

To help balance the top coils, I will also reduce the height the raised supports (which are actually excess AA battery holders, black in color) that are holding the magnet and rod away from the top of the coil. The greater proximity may mean that I should not need a fifth coil. We will see though.

I have not released a video showing the problem with the new commutator with the large 32" fan at 300V... the results sucked without comparison to anything I produced with the exception of the setup described just a few posts above (i.e. putting the coils in parallel powered by parallel battery packs, of which I have (unregrettably) no video of whatsoever).