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Author Topic: Study of Generator Coil Acceleration Under Load (moderated)  (Read 30007 times)

wattsup

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #30 on: January 19, 2016, 04:14:18 PM »
@gotoluc

As usual good work in trying to define that effect. I made a post but forgot to post it before I left for the office, so I will make this quick.

The metglass lams are placed horizontal in your set-up and the rotating magnet is also horizontal but smack dab aligned to the center of the metglass. What I think is happening is the center 3rd of the metglass icore which is closest to the magnet passage is getting all the impress leaving very little to the top and bottom 3rds which are the ones the coil will see and react to as change. Maybe realign the magnet so its closest point is aligned with the top or bottom 3rd and try your test again. See if the metglass now does the same as the rod.

Thanks for your works man.

Added: I forgot to also mention this.

You did not talk about that vertical pancake coil next to the magnet. It is also probably affecting the metglass as an impress brake more then it does on the regular rod, so maybe try connecting and disconnecting that coil as well.

wattsup


gotoluc

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #31 on: January 19, 2016, 04:43:31 PM »
@gotoluc

As usual good work in trying to define that effect. I made a post but forgot to post it before I left for the office, so I will make this quick.

The metglass lams are placed horizontal in your set-up and the rotating magnet is also horizontal but smack dab aligned to the center of the metglass. What I think is happening is the center 3rd of the metglass icore which is closest to the magnet passage is getting all the impress leaving very little to the top and bottom 3rds which are the ones the coil will see and react to as change. Maybe realign the magnet so its closest point is aligned with the top or bottom 3rd and try your test again. See if the metglass now does the same as the rod.

Thanks for your works man.

Added: I forgot to also mention this.

You did not talk about that vertical pancake coil next to the magnet. It is also probably affecting the metglass as an impress brake more then it does on the regular rod, so maybe try connecting and disconnecting that coil as well.

wattsup

Hi wattsup,

it makes no difference to the effect if I raise or lower the rod in relation to the center of the magnet rotor.

Luc

MileHigh

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #32 on: January 19, 2016, 05:10:02 PM »
Well, I am baffled because the clip shows that the "effect" is exactly what I said it was.  It has nothing to do with the choice of core material and everything to do with the magnitude of the mechanical load on the prime mover.  In this experiment all that you have to do is measure the electrical load due to the coils and load resistors and that becomes the mechanical load on the prime mover.   Eddy current losses and hysteresis losses also simply become more of a mechanical load on the prime mover and also act to slow it down.

Starting at about 20:00 minutes into the clip you have the most dramatic "acceleration under load" when the 10-ohm resistor gets changed to the 1-ohm resistor.  Luc even acknowledges that the electrical load decreases when he does this.

With the 10-ohm resistor, the total electrical load is about 1.58 watts.

Then the load resistor is changed to 1-ohm, the prime mover speeds up, and the total electrical load is about 0.98 watts.

So, "acceleration under load" is really "acceleration (to a higher final RPM) under reduced load."  In that sense there is no "effect."

verpies

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #33 on: January 22, 2016, 03:26:09 PM »
Okay everyone, I made the video as promised...
Link to the movie: https://www.youtube.com/watch?v=NYGM4UlnqTM
Good video!  I agree with your experimental methodology and manner of analysis and reasoning.

I see a mathematical mistake in it though.

There are several 2-variable formulas for calculating average power, such as:
P=V*i
P=V2/R
P=R*i2
...and there seems to be confusion when to use an RMS value and when to use the arithmetical MEAN value, in these formulas.

The distinction is very simple: 
- If you see a squared current or voltage in the formula, then you should use the RMS value for it.
- If you see a non-squared current or voltage in the formula, then you should use the MEAN value for it.

IMPORTANT: In the formulas above, only one variable can vary in time and the second variable must be constant (it cannot vary in time). 
If both variables vary in time, then you must use an oscilloscope and its MATH function to calculate power one instance at a time, by multiplying 2 channels and averaging the results, unless the current and voltage have exactly the same shape and you know their exact phase offset.

According to the rules above, it was perfectly fine to use the RMS voltage in the formula P=V2/R  to calculate the average power dissipated in a 10Ω resistor, because its resistance was constant (10Ω) while the voltage across it was variable and squared in the formula.

But it was not OK to use the RMS current to calculate the power supplied to the "JobMate" motor according to the formula P=V*i  although the supply voltage was constant at 28VDC, because the current in this formula was not squared .


P.S.
Some multimeters are capable of calculating the RMS values of non-sinusoidal waveforms ...up to a certain frequency.
e.g. my Fluke 87 can do it and I just recently verified it on a 330Hz sawtooth waveform.
« Last Edit: January 22, 2016, 05:41:26 PM by verpies »

verpies

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #34 on: January 22, 2016, 05:17:16 PM »
You did not talk about that vertical pancake coil next to the magnet. It is also probably affecting the metglass as an impress brake more then it does on the regular rod, so maybe try connecting and disconnecting that coil as well.
That coil does not exert any influence on the rotor because no significant current is allowed to flow through it.
A coil without current might not as well exist at all.

gotoluc

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #35 on: January 22, 2016, 05:56:45 PM »
Hi verpies,

you may not of noticed but the meters measuring the supplied voltage and current for the prime mover (jobmate) are set up as a Low Pass Filter.
I call it my cap bank meters which are permanently setup as a low pass filter (see pics) where the current (right DMM) is measuring the DC voltage across a 0.1 Ohm  resistor which is connected between the right 3,900uf capacitor to the left 3,900uf capacitor. The left DMM is measuring the voltage across the left capacitor which includes the voltage drop.

Knowing this I now believe you would agree the test data to be correct?

Thanks for your help

Luc

verpies

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #36 on: January 22, 2016, 06:15:21 PM »
you may not of noticed but the meters measuring the supplied voltage and current for the prime mover (jobmate) are set up as a Low Pass Filter.
Indeed, I have not noticed.
A low Pass Filter with low enough cutoff frequency is effectively an averaging circuit.
But I would add small ceramic or film capacitors in parallel with the big electrolytic caps because big caps can have a high ESR at higher frequencies that lets those through.

The left DMM is measuring the voltage across the left capacitor which includes the voltage drop.
So the energy flows form the right cap to the left cap?

Knowing this I now believe you would agree the test data to be correct?
Yes, the input power of the prime mover was correctly calculated.

gotoluc

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #37 on: January 22, 2016, 06:38:30 PM »
So the energy flows form the right cap to the left cap?

No, the Left cap is the DC input filling Right cap (through resistor) and why I mentioned the left DMM is measuring the voltage across the right cap since there will be a voltage drop caused by the resistor.

I also had a 100000uf cap between the prime mover and the low pass filter output cap to make sure there was a smooth transition between the two.

I agree on adding a 0.1uf across the low pass filter output cap. But for the low frequency the prime mover was I'm sure it was adequate.
I'll add it in case I use it for high frequency work.

When ever DC is being switched on and off, I always use this low pass filter metering system. I suggest everyone to build one for this purpose which makes measurements simple and accurate.

Thanks for your help

Luc

verpies

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #38 on: January 22, 2016, 07:54:08 PM »
No, the Left cap is the DC input filling Right cap (through resistor) and why I mentioned the left DMM is measuring the voltage across the right cap since there will be a voltage drop caused by the resistor.
That's wrong.  For input power measurements purposes, the voltage should be measured AFTER the voltage drop caused by the CSR.
Otherwise you are also measuring the power dissipation of the CSR.

gotoluc

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #39 on: January 22, 2016, 08:02:57 PM »
That's wrong.  For input power measurements purposes, the voltage should be measured AFTER the voltage drop caused by the CSR.
Otherwise you are also measuring the power dissipation of the CSR.

I don't know where the confusion is but I tried my best to describe the voltage is measured after the CSR voltage drop!

re-read the below

No, the Left cap is the DC input filling Right cap (through resistor) and why I mentioned the left DMM is measuring the voltage across the right cap since there will be a voltage drop caused by the resistor.

Luc 

wattsup

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #40 on: January 23, 2016, 04:58:53 PM »
@gotoluc

Below is an image I grabbed from your first video showing the position of the magnet versus the iron core.

What I am just curious to know is what was the process you used to finally decide to position your spinning magnet at that particular location? I think everything starts with that one consideration since nothing in the other variables could compensate for any loss of impress caused by a potential faulty fixed magnet/core position, maybe faulty is not the right word, maybe saying less favorable would be more appropriate.

Another way of asking this is..... how sure are you that the magnet-to-core position is the optimal position for this type of experiment where the initial premise is that the core is receiving the maximum degree of magnetic change in order to impart that change to the coil? If that one consideration is optimized, would that optimal performance leave any room for any acceleration under load or is the acceleration due to the fact that the magnet to core relation was not optimized and hence any other change on the core now has room to influence the drag level on the prime mover. Again hard to explain. hahaha

Instead of making a video I am just posting another image showing a simple pair of magnets in attraction mode so their N/S poles are facing out secured on a simple drill shaft and a compass. With these two simple toys you can very  quickly do micro tests for core to magnet positioning. The magnet is very easy to turn with your fingers and see some pretty crazy differences in effects when held horizontal or vertical to the compass or when the compass itself is held horizontal or vertical to the magnet. You soon realize that one or the other relative to the Earth plane also makes for some very curious and contradictory effects.

I also use this on my drill to test other effects in angular spin. I use another pair as this but having both poles out as north and another with both out as south. Very easy tools for magnetic effects.

The final diagram I have made is to show something else. I have a very bad feeling that when a round magnet passes in front of a round core and coil, the actual passage generates more cancelled impress then the impress that can actually produce output, output which is only occurring because through this very complex magnet to core to coil interchange that is happening on on such circular geometries.

The diagram shows several coil geometries relative to the same magnet passage. The second group shows ways of keeping the magnet only on one half of the core/coil so that the massage can generate a more "directional" impress that would favor more "directional" output, versus the standard method we use where the magnet arrives at the coil/core from the left side first, (ok - good), then splits to the top and bottom of the coil (bad - causing extreme cancellation) then leaving them on the other side (good - but not great).

The coil/core #7-8 and #9-10 are the ones I believe will be the most productive because each only receives one constant and directional impress so the cancellation should be held to a minimum.

This is just theory right now but I wanted to put this out there in case others are consider any line of experimentation where such considerations could be easily added as tests in the same process.

wattsup

PS: Hope this is not tooooooo of topic.


verpies

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #41 on: January 23, 2016, 05:39:05 PM »
I don't know where the confusion is
Probably from the lack of a diagram.  As you probably heard - a picture is worth a 1000 words.

Did you have Diag.5B in mind ?:

gotoluc

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #42 on: January 23, 2016, 07:00:18 PM »
Did you have Diag.5B in mind ?:

Close but the below is the exact setup of metering of the DUT

Now it should be clear for anyone to build one of these for their own accurate input power tests.

Luc

gotoluc

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #43 on: January 23, 2016, 07:17:12 PM »
@gotoluc

Below is an image I grabbed from your first video showing the position of the magnet versus the iron core.

What I am just curious to know is what was the process you used to finally decide to position your spinning magnet at that particular location? I think everything starts with that one consideration since nothing in the other variables could compensate for any loss of impress caused by a potential faulty fixed magnet/core position, maybe faulty is not the right word, maybe saying less favorable would be more appropriate.

Another way of asking this is..... how sure are you that the magnet-to-core position is the optimal position for this type of experiment where the initial premise is that the core is receiving the maximum degree of magnetic change in order to impart that change to the coil? If that one consideration is optimized, would that optimal performance leave any room for any acceleration under load or is the acceleration due to the fact that the magnet to core relation was not optimized and hence any other change on the core now has room to influence the drag level on the prime mover. Again hard to explain. hahaha

Instead of making a video I am just posting another image showing a simple pair of magnets in attraction mode so their N/S poles are facing out secured on a simple drill shaft and a compass. With these two simple toys you can very  quickly do micro tests for core to magnet positioning. The magnet is very easy to turn with your fingers and see some pretty crazy differences in effects when held horizontal or vertical to the compass or when the compass itself is held horizontal or vertical to the magnet. You soon realize that one or the other relative to the Earth plane also makes for some very curious and contradictory effects.

I also use this on my drill to test other effects in angular spin. I use another pair as this but having both poles out as north and another with both out as south. Very easy tools for magnetic effects.

The final diagram I have made is to show something else. I have a very bad feeling that when a round magnet passes in front of a round core and coil, the actual passage generates more cancelled impress then the impress that can actually produce output, output which is only occurring because through this very complex magnet to core to coil interchange that is happening on on such circular geometries.

The diagram shows several coil geometries relative to the same magnet passage. The second group shows ways of keeping the magnet only on one half of the core/coil so that the massage can generate a more "directional" impress that would favor more "directional" output, versus the standard method we use where the magnet arrives at the coil/core from the left side first, (ok - good), then splits to the top and bottom of the coil (bad - causing extreme cancellation) then leaving them on the other side (good - but not great).

The coil/core #7-8 and #9-10 are the ones I believe will be the most productive because each only receives one constant and directional impress so the cancellation should be held to a minimum.

This is just theory right now but I wanted to put this out there in case others are consider any line of experimentation where such considerations could be easily added as tests in the same process.

wattsup

PS: Hope this is not tooooooo of topic.

Hi wattsup,

It's just tooooooo much to read.  Please ask one question at a time. I've lost interest in this effect some years back and even more now that I've been able to test it with a quality core like Metglas.

I'll answer your first question:
The reason the core is placed on the end of the magnet is for mechanical reasons. For example is it was on the opposite end it would cause much more pull on the shaft of the Dremel tool which causes flex and at a certain rpm can cause vibration aka harmonics.

Luc

verpies

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Re: Study of Generator Coil Acceleration Under Load (moderated)
« Reply #44 on: January 23, 2016, 09:22:01 PM »
Close but the below is the exact setup of metering of the DUT
All is clear now.
This system is accurate if the caps are huge (yours are) and have low impedance at all the frequencies generated by the DUT.
The brush noise of a universal motor can contain frequency components well in the MHz region.