Electric Motor Secrets

[Peter Lindemann]

Not Sure about this method

Ok, I replaced the bearings with self aligning ones and got the motor running.
Everything seems fine now and I can run the motor for as long as I want with no change in speed. So I went on to measure the efficiency.
After gathering some data and calculations, the numbers seemed bad. I loaded the motor 8mm shaft several times and each time with different force, but all the calculations showed efficiencies 31% and below
For example, here is data from one of the tests:

Input power: 25.5V, 2.47A.
RPM's 4146
Scale deflection: 1.28Lbs on one scales and 0.71Lbs on other scales.

So the input power is 25.5v x 2.47a = 62.99W or 0.0844 Hp

The shaft diameter is 8mm so the circumference is 8xphi or 8x3.1416=25.13mm or 0.0824 Ft

RPM x Ft / 60 = 4146x0.0824/60=5.69 Ft/s

5.69Ft/s x (1.28Lbs+0.71Lbs)= 11.32 Ft-Lbs/s or 0.0205 Hp

So Efficiency is output/input or 0.0205/0.0844=0.242 or 24% efficiency.
Is this right? Seems too bad. The other results are similar.

Maybe I measured the deflection on scales wrong? I did this the following way. I put the motor so that the shaft end is reaching past the table top, then I attached a piece of thin cloth sheet to the scales. I turned the scales ON and just let them hang on the shaft using the cloth sheet. To the load was just the weight of the scales. This way I could get steadier results, because it is difficult to load the motor evenly if you hold the scales above the motor in your hands. Maybe this is the wrong way to do this?
I am a bit confused about these results

Jetijs,

Your description of how the scales are used is confusing. It does not sound right, though. Hanging the scales on the motor shaft just weighs the scales. This is not what you want. Also, I don't think your digital scales are the right kind for this measurement. They seem built to weigh objects by having them placed ON the scale. Also, your cloth sheet does not seem to be able to produce the appropriate amount of friction to load the shaft.

The input voltage, input current, scale deflections AND the RPM (under load) all must be registered simultaneously to do the calculations. This produces a POWER reading. To actually calculate WORK, the readings must be maintained for a TIMED RUN.

Doing the Dynamometer test is a bit tricky. It is very difficult to do just using a small shaft as the "wheel of known circumference".

You are going to have to think this through, and maybe get some different scales.

Peter

[elias]

I suppose ...

Jetijs,

Don't get discouraged, I think that your have great error in reading your spring scales. You should load your motor more than this so the error in your readings gets negligible in comparison to the load your motor has. Also I think that an 8mm shaft is too small for much precise readings. You'd better use a large wheel like peter does for measuring the applied torque of your motor. I am looking forward to see better results. Also I suppose that you can increase the efficiency of your motor by running it on more voltage.

How does your spring scales stand on there? without falling due to the rotation of your shaft.

Elias

[satchid]

Hi all,
I am Willy Gooris from Belgium and new in this Forum. My interest go's heavily towards this motor and read all the post in this tread. I ordered the motor DVD from Peter.


Lighty, I admire your knowledge.

You used UCC3732x driver in the motor controller,

Due to availability of material here, Is there a replacement for the ucc37321 controller from Maxim?

Thanks,

Willy

[Jetijs]

Peter,
I made a crude drawing, that should explain how I measured the deflection on the scales:

http://www.emuprim.lv/bildez/images/viskautkas_labs/visadi_strunti_1/table.GIF

(don't laugh, I am not an artist )
This way we can also attach a bigger weight to the scales and load the motor more. One person just needs to look that the leather strip remains where it is and doesn't fall off the shaft.
The scales I am using are very similar to such ones:
Handy Portable Hanging Digital Electronic Scale - blue - eBay (item 160235158312 end time May-28-08 11:11:02 PDT)

If both scales show a deflection, is it right that I must use the sum of both readings in my calculations? This was not clear in your video, because you just had a deflection on one scale. Also, If we have an object of known weight, can we just hang that object on the shaft/wheel just like in the picture above and do the tests this way? I mean this way we already know the weight of that object and need just write down the voltage, amperage and RPM's. Or is this a stupid idea?

Elias, The scales need to be held gently in place bu another person, because if not, they indeed would fall down We just found that if we load the shaft using the scales like Peter showed, the readings on the scales change very fast and it is not easy to get a steady reading, because a person can not load the motor with steady load using his hands. But if the scales just hang down, one person just needs to hold the leather strip in place and the readings and load are steady and don't change in the process of measuring.

Ok, I will go for the wheel then.
24% seems strangely small

[Peter Lindemann]

Different Scales

Peter,
I made a crude drawing, that should explain how I measured the deflection on the scales:

http://www.emuprim.lv/bildez/images/viskautkas_labs/visadi_strunti_1/table.GIF

(don't laugh, I am not an artist )
This way we can also attach a bigger weight to the scales and load the motor more. One person just needs to look that the leather strip remains where it is and doesn't fall off the shaft.
The scales I am using are very similar to such ones:
Handy Portable Hanging Digital Electronic Scale - blue - eBay (item 160235158312 end time May-28-08 11:11:02 PDT)

If both scales show a deflection, is it right that I must use the sum of both readings in my calculations? This was not clear in your video, because you just had a deflection on one scale. Also, If we have an object of known weight, can we just hang that object on the shaft/wheel just like in the picture above and do the tests this way? I mean this way we already know the weight of that object and need just write down the voltage, amperage and RPM's. Or is this a stupid idea?

Elias, The scales need to be held gently in place bu another person, because if not, they indeed would fall down We just found that if we load the shaft using the scales like Peter showed, the readings on the scales change very fast and it is not easy to get a steady reading, because a person can not load the motor with steady load using his hands. But if the scales just hang down, one person just needs to hold the leather strip in place and the readings and load are steady and don't change in the process of measuring.

Ok, I will go for the wheel then.
24% seems strangely small

Jetijs,

There are a couple of problems here. First of all, just hanging the scales on the shaft will not measure "torque". Second, your digital scales are probably not going to work because their sampling rate is too fast, and you may never get a stable reading. I highly recommend that you use an ANALOG, spring based scale for these readings, like I did. Third, the technique is such that if there are readings on both scales, the value is the DIFFERENCE between them, not the SUM. I recommend that you watch my demonstration over and over until you fully understand the process.

From what I can tell, you have not measured any of the mechanical energy producing capabilities of the motor yet.

Also, you need to modify your circuitry (by inserting a low ohm current measuring resistor) in the circuit going to the power coils. You should also take the output from the output coil and apply it directly back to the capacitor, and not the way you show it in the schematic drawing. Right now, you can't measure anything discreetly because currents are going back and forth on common ground buses and such. Input pathways and output pathways must be discreet and distinct for proper measuring.

Right now, you are only measuring the NET input. We need to know the TRUE power consumption of the coils. Your mechanical energy production should be at least 60% of the power going to the coils, not 60% of the NET input.

You may also have to watch the wave form on the scope while you do the DYNO test, to see what the input wave form is doing. If you slow the motor down too much during the test, the current wave form may flatten out on the top, lowering the electrical energy return. So, there may be a specific speed that optimizes all of these effects. You have to find that "optimum window" and test the motor there. Once COP>1 operation is measured in that window, then further circuit modifications can be engineered so the motor will operate at that efficiency in a wider speed range.

there is a lot more to do to test this motor properly. Please don't be in a hurry.

Peter

[satchid]

dyno

Hi Peter,

I just stumbled on this simple to make dyno .

Sci-Spot.com - Dynamometer

Might be something to adapt for the future? Would this be working?

Willy

[Jetijs]

Peter,
I can't find those shunts in the electronics shops here. I mean, there are some of them but they cost about 40$ a piece I will rather take apart some 5$ worth multimeters and get a shunt from them. Also In reality my output leads are connected directly to the capacitor terminals, the circuit drawing is incorrect. I will redraw and post the corrected drawing. In these tests the output winding leads were connected to the capacitor on the input section and the amp meter was connected on the negative lead just before the capacitor and diode. This way it showed what the motor actually consumes and not what it was drawing from the power supply, because the power supply amp readings were lower. I already sent my drawings to the guy who will make the wheel for me (my own attempts failed miserably). As for the scales, before I bought these, I searched all aroud the web and local shops for scales like yours with no much luck. I even went to a chemist equipment shop, but they said, that no one uses such scales anymore, they couldn't even tell where I could get ones. Anyway, I will get the wheel done (with the curcumference exactly 1Ft) and then try these tests again with the scales I already have, then we will see
Thank you,
Jetijs

[lighty]

Hi all,
I am Willy Gooris from Belgium and new in this Forum. My interest go's heavily towards this motor and read all the post in this tread. I ordered the motor DVD from Peter.


Lighty, I admire your knowledge.

You used UCC3732x driver in the motor controller,

Due to availability of material here, Is there a replacement for the ucc37321 controller from Maxim?

Thanks,

Willy

You can use some other MOSFET/IGBT driver from IR or ST. However, I tested various drivers over the years the UCC3732x ones proved as one of the best when dealing with a high degree of transients and EMI. They're also one of the most stable ones I saw in that price range. There are some even faster, more stable ones but they cost much more and they require additional parts in order to work and in this particular case I think they're not worth the trouble.

As for the UCC3732x ones I usually order them from Farnell and AFAIK you have Farnell representative in Belgium (they hold impressive selection of semiconductors). Look at Farnell NL | 's Werelds voornaamste distributeur van elektronische, elektrische en industriële (MRO) componenten en producten.


Regards

lighty

[aladinlamp]

Peter,
I can't find those shunts in the electronics shops here. I mean, there are some of them but they cost about 40$ a piece I will rather take apart some 5$ worth multimeters and get a shunt from them. Also In reality my output leads are connected directly to the capacitor terminals, the circuit drawing is incorrect. I will redraw and post the corrected drawing. In these tests the output winding leads were connected to the capacitor on the input section and the amp meter was connected on the negative lead just before the capacitor and diode. This way it showed what the motor actually consumes and not what it was drawing from the power supply, because the power supply amp readings were lower. I already sent my drawings to the guy who will make the wheel for me (my own attempts failed miserably). As for the scales, before I bought these, I searched all aroud the web and local shops for scales like yours with no much luck. I even went to a chemist equipment shop, but they said, that no one uses such scales anymore, they couldn't even tell where I could get ones. Anyway, I will get the wheel done (with the curcumference exactly 1Ft) and then try these tests again with the scales I already have, then we will see
Thank you,
Jetijs

i bought 2 sets of these, 10 days to arrive to Europe

6 Spring Scales 250 to 5000 Gram/Newtons Scale Balance - eBay (item 190219869236 end time May-11-08 11:01:02 PDT)

[Jetijs]

Thanks aladinlamp
They seem exactly what I need

[Peter Lindemann]

Perfect Scales

Thanks aladinlamp
They seem exactly what I need

Jetijs,

These are exactly the kind of scales I use. Get two sets, like AladinLamp did. Then, you'll be ready to measure torque in any power range you want.

Thanks, AladinLamp!!!!

Peter

[aladinlamp]

Thanks aladinlamp
They seem exactly what I need

Np,
by the way, what do you plan to do with your Lindemann attraction motor V1.0
Do you still need it, use it ...?

Thanx

[satchid]

As for the UCC37321 ones I usually order them from Farnell and AFAIK

Lighty,
Thank you, i ordered 10 .

Willy

[Jetijs]

Np,
by the way, what do you plan to do with your Lindemann attraction motor V1.0
Do you still need it, use it ...?

Thanx

The V1.0 is assembled and is sitting on the shelf. I use it as a demonstration model that I can show people who are interested. It is easy to explain what the motor is doing using that model
Thanks,
Jetijs

[theremart]

Replicating Elias motor...

I have picked up 4 cheap $4.00 each dc motors, that I hope to convert to Peter's style of motor. This is a permanent magnet motor, so, my plan is to pull out the magnets and to place in some hand wound coils.

This is a 12V over 3,000 rpm motor not much torque as it is now.

The commutator sure put drag on this motor, I am surprised it put out as much as it did with this much drag.

Anyhow.... will cut off the coils and plan how I will cut down the stator.

Mart