Motor Generators

[Rakarskiy]

Hi Rakarskiy,
I noticed you say "LATR is essentially a voltage divider". I am not familiar with term LATR, but from some limited Google info and appearance of component in your diagram, it would seem to be what is commonly referred to as a variac, which is an adjustable autotransformer. Therefore it can not be treated as a voltage divider.
Rregards,
bi

I am attaching an autotransformer circuit (LATR - laboratory autotransformer).
If you look at the circuit and label the winding parts as resistances, you get exactly what I'm talking about.
There is practically no reactance under load. Only the active resistance of the wires remains. Thus, it is absolutely acceptable to use the system as a voltage divider.
Sincerely.
2023-04-04_231249.jpg

The fact that the directions of the currents are slightly different in reality than in the diagram (which I took from Wikipedia) from a resistive divider is not reflected in any way in the voltage division in the sections.

[bistander]

I am attaching an autotransformer circuit (LATR - laboratory autotransformer).
If you look at the circuit and label the winding parts as resistances, you get exactly what I'm talking about.
There is practically no reactance under load. Only the active resistance of the wires remains. Thus, it is absolutely acceptable to use the system as a voltage divider.
Sincerely.
2023-04-04_231249.jpg

The fact that the directions of the currents are slightly different in reality than in the diagram (which I took from Wikipedia) from a resistive divider is not reflected in any way in the voltage division in the sections.

Hi Rakarskiy,
You are mistaken. You say:
"Thus, it is absolutely acceptable to use the system as a voltage divider."
This is untrue. Take a few minutes and learn about it. The device is a transformer and must be treated as such.
bi

https://www.electronics-tutorials.ws...ansformer.html

[Rakarskiy]

You didn't convince me. Firstly, this is the direction of current strength (I [A]) and voltage (U [V]) in a real circuit, they are opposite.
What is hung in such educational books does not in any way reflect the real movement of current. In the experiment, there was just a divider effect (voltage reduction system)
Take half the period of the voltage sine wave and see how it looks in all areas. Do not forget that this transformer has a zero terminal, it always has zero.

2023-04-05_180601.jpg

The ratio of EMF values is expressed by the formula: E1 / E2 = w1 / w2 = k, where E is the EMF, w is the number of turns, k is the transformation ratio.
Considering that the voltage drop in the transformer windings is small, it can be ignored. In this case, the equalities: U1 = E1; U2 = E2 can be considered fair. Thus, the above formula becomes: U1/U2 = w1/w2 = k, that is, the ratio of voltages to the number of turns is the same as for a conventional transformer.
Without going into details, we note that the ratio of the current strength of the upper coil to the load current, as for a conventional transformer, is expressed by the formula: I1/I2 = w2/w1 = 1/k. It follows that since in the step-down transformer w2 < w1, then I2 < I1. [In other words, the output current is much less than the input current.] Thus, less energy is spent on heating the wire, which allows the use of smaller wires.

[In other words, the output current is much less than the input current.]
I think this phrase is enough not to think that more than I calculated was put on the generator rotor. The СOP ratio is maintained.

https://rakatskiy.blogspot.com/2022/...ransducer.html

An autotransformer efficiency of 99% can only be achieved with a small difference between the input and output voltages.
In the experiment 220/117 = 1.88 (almost double the difference), thus no more than 0.6 [45 W (in) * 0.6 = 27 W (out)]
I think the rest of the discussion doesn't make sense anymore

[bistander]

...
[In other words, the output current is much less than the input current.]
I think this phrase is enough not to think that more than I calculated was put on the generator rotor. The СOP ratio is maintained.
...

Who wrote that quote (shown in bold)?
bi
{edit}
Added test photo and data.
IMG_20230405_124955912_copy_800x600.jpg

Meters on left read input. 119.7 Vac & 0.87A. meters on right are output into resistor. 25.23Vac & 2.74A.
120 step down to 25 Volts. 2.74A obviously higher than 0.87A.

That quoted statement is wrong. And the variac or autotransformer cannot be modeled using a voltage divider (resistor network) as you claim.

Test and photo taken 5April2023 by bi.

[Rakarskiy]

You may be right that the resistive divider equation is wrong. The quote is taken from the electrician training website. Only I understood what is meant, the current that appears in the second part of the winding consists of the current of the primary winding at the output to the load circuit. Thus, there is no need for a secondary winding. This is implied.

But your example is (input) 119V*0.87A = 103W, (output) 25V * 2.7A = 67W. Thus, the conversion efficiency is 0.65.

If in the experiment we have 45 W at the input of the autotransformer, then at the output we will get no more than 0.6-0.7 of the input power:
0.6*45W=27W (0.7 * 45 W = 31 W) - /this is at the input to the rotor winding/
At the output we have 46 W. Conversion efficiency 46/27=1.7 (46/31 = 1.48).

So, still more than one.
Sincerely.

[bistander]

You may be right that the resistive divider equation is wrong. The quote is taken from the electrician training website. Only I understood what is meant, the current that appears in the second part of the winding consists of the current of the primary winding at the output to the load circuit. Thus, there is no need for a secondary winding. This is implied.

But your example is (input) 119V*0.87A = 103W, (output) 25V * 2.7A = 67W. Thus, the conversion efficiency is 0.65.

If in the experiment we have 45 W at the input of the autotransformer, then at the output we will get no more than 0.6-0.7 of the input power:
0.6*45W=27W (0.7 * 45 W = 31 W) - /this is at the input to the rotor winding/
At the output we have 46 W. Conversion efficiency 46/27=1.7 (46/31 = 1.48).

So, still more than one.
Sincerely.

Well I'm pleased you recognize your mistake. It is also a mistake to assume the single point efficiency shown in my test would apply elsewhere. The variac is sensitive (rating wise) to current and my test point was near the upper limit for the old variac. Other points which I ran yesterday at lower currents showed markedly higher efficiency. I've saved several meter snapshots. When I get a few minutes, I'll add some data here via edit.
bi
edit

IMG_20230405_124750962_copy_800x600.jpg

This was at the same load point but a bit sooner before the variac heated. I read 0.77A putting efficiency at 76%.

And another, at lighter load.
IMG_20230405_131032964_copy_800x600.jpg

Looks like 89%.

[Rakarskiy]

This is no longer trivial, the conversion efficiency in the conducted experiment (approximately, as before) is greater than unity. In addition, the experiment was conducted roughly, without finding the optimal mode. Also, at first I took this to be a confirmation of the academic topology of the generators, but over time I looked and found a confirmation of the correct process topology.

[bistander]

This is no longer trivial, the conversion efficiency in the conducted experiment (approximately, as before) is greater than unity. In addition, the experiment was conducted roughly, without finding the optimal mode. Also, at first I took this to be a confirmation of the academic topology of the generators, but over time I looked and found a confirmation of the correct process topology.

Rakarskiy,
you believe what you want. You are wrong.
bi

[spark2]

Hey Rakarskiy
nice work on your pdf liked it.
For voltage dividers we can use resistors, capacitors and even coils as a divider, nice job.
see here for those who want to learn and use the right formulas.

https://www.omnicalculator.com/physics/voltage-divider

[bistander]

Hey Rakarskiy
nice work on your pdf liked it.
For voltage dividers we can use resistors, capacitors and even coils as a divider, nice job.
see here for those who want to learn and use the right formulas.

https://www.omnicalculator.com/physics/voltage-divider

Hi spark2,
if you have comprehended the posts between rakarskiy and myself over the past 2 days, he admitted he was in error to use the voltage divider equation for the variac. You must use the appropriate model and equations which are those for an autotransformer. Or better yet, use actual measurements.The link I provided previously explains it well. See: https://www.electronics-tutorials.ws...ansformer.html
bi

[Turion]

From someone who has a REPLICA of my (generator) machine and has been doing testing. (Since he machined BOTH generators, I'd say it is a fairly close replica.)

----------------------------------------------
#12 .. This test I had (10) of my ferrite cores in the machine... no load and spun it up to 3200rpm. Slipped in the other (2) ferrite cores and took notes : Speed 3200rpm- unchanged .... Voltage @242-243vac. Pulled (2) ferrite cores , speed still @3200rpm...slipped in (2) steel wire cores (like I sent you all taped up in case they blew !) and RPM just nose dived. Couldn't take time to check as could be possible meltdown in progress. Checked voltage @ 385vac RPM ,best guess probably about 2000 by now. Just for giggles switched the single heat lamp on and no light. Pulled cores..total run time no more than 2 min. Very hot, could not continue. Immediate speed up to 3200rpm again. Dropped in (2) ferrite cores and no change. CONCLUSION : Who ever said that there is no cog at high speed is full of ****. (2) steel cores bogged mine down to slightly over half speed with no load. The ferrite, not so much, but I never pulled them ALL out and tested either.
-----------------------------------------------

https://youtu.be/J18E2KTugOY

This is just a video of the generator and the solenoid system to move cores in and out for testing purposes. With ferrite cores, the solenoids are not necessary, so he was going to remove them. Until he TESTED and found out what would happen with a core material that outputs REAL power. As he shared ABOVE. With the existing ferrite cores the machine can start with the cores already in place, but it is EASIER on the motor to do a "soft start" with NO cores in place. It would be IMPOSSIBLE to start the machine with 12 of the cores I am using in place. The motor would not turn the rotor at all, and would simply burn up. The reason for adding the solenoids in the FIRST PLACE was to see if bistander's "claim" that there is no cogging at speed was credible. If you want to use playdough cores, it might be, but if you want to use cores that put out maximum power from the generator coils, it is a load of CRAP.

When you are using core material that PRODUCES high magnetic flux, there is COGGING, even at HIGH SPEED. Magnetic neutralization, as I have described it, simply produces a magnetic reaction with the core at the correct instant in time that is the direct OPPOSITE of that which is caused by the rotor magnets and NEUTRALIZES the negative cogging effect the rotor magnets cause. Magnetic Neutralization. The cores I am using, because of their high iron content, cause cogging at high speed. But they also put out POWER, where ferrite does not. With ferrite cores, the output of the generator coil is FAR from acceptable, which is why I do NOT use them. These are the facts. Do whatever you want with them.

What we have learned is resulting in the build of yet ANOTHER machine, where the magnetic neutralization is isolated from the generating phase, and even better results are possible, but that's beside the point. What I have stated about COGGING and MAGNETIC NEUTRALIZATION is true. Believe it or DON'T.

[bistander]

From someone who has a REPLICA of my (generator) machine and has been doing testing. (Since he machined BOTH generators, I'd say it is a fairly close replica.)

----------------------------------------------
#12 .. This test I had (10) of my ferrite cores in the machine... no load and spun it up to 3200rpm. Slipped in the other (2) ferrite cores and took notes : Speed 3200rpm- unchanged .... Voltage @242-243vac. Pulled (2) ferrite cores , speed still @3200rpm...slipped in (2) steel wire cores (like I sent you all taped up in case they blew !) and RPM just nose dived. Couldn't take time to check as could be possible meltdown in progress. Checked voltage @ 385vac RPM ,best guess probably about 2000 by now. Just for giggles switched the single heat lamp on and no light. Pulled cores..total run time no more than 2 min. Very hot, could not continue. Immediate speed up to 3200rpm again. Dropped in (2) ferrite cores and no change. CONCLUSION : Who ever said that there is no cog at high speed is full of ****. (2) steel cores bogged mine down to slightly over half speed with no load. The ferrite, not so much, but I never pulled them ALL out and tested either.
-----------------------------------------------

https://youtu.be/J18E2KTugOY

This is just a video of the generator and the solenoid system to move cores in and out for testing purposes. With ferrite cores, the solenoids are not necessary, so he was going to remove them. Until he TESTED and found out what would happen with a core material that outputs REAL power. As he shared ABOVE. With the existing ferrite cores the machine can start with the cores already in place, but it is EASIER on the motor to do a "soft start" with NO cores in place. It would be IMPOSSIBLE to start the machine with 12 of the cores I am using in place. The motor would not turn the rotor at all, and would simply burn up. The reason for adding the solenoids in the FIRST PLACE was to see if bistander's "claim" that there is no cogging at speed was credible. If you want to use playdough cores, it might be, but if you want to use cores that put out maximum power from the generator coils, it is a load of CRAP.

When you are using core material that PRODUCES high magnetic flux, there is COGGING, even at HIGH SPEED. Magnetic neutralization, as I have described it, simply produces a magnetic reaction with the core at the correct instant in time that is the direct OPPOSITE of that which is caused by the rotor magnets and NEUTRALIZES the negative cogging effect the rotor magnets cause. Magnetic Neutralization. The cores I am using, because of their high iron content, cause cogging at high speed. But they also put out POWER, where ferrite does not. With ferrite cores, the output of the generator coil is FAR from acceptable, which is why I do NOT use them. These are the facts. Do whatever you want with them.

What we have learned is resulting in the build of yet ANOTHER machine, where the magnetic neutralization is isolated from the generating phase, and even better results are possible, but that's beside the point. What I have stated about COGGING and MAGNETIC NEUTRALIZATION is true. Believe it or DON'T.

Hi turion,

It is not cogging that is happening at speeds like that, but core loss. It is acting like a magnetic brake, combination of eddy current and hysteresis converting energy to heat. That is taking torque loading the drive motor.

If you actually read and understood my comments about cogging and speed, you'd realize that I didn't say "no cogging at speed", but rather the effects of cogging diminished as speed increased due to the counter effects of the rotor's momentum, such that at reasonably high RPM, cogging becomes unnoticed.

On the other hand, core loss increases nearly exponentially with increase in RPM.

The core loss with iron cores proved higher than that of ferrites, no surprise. Also note there was higher induction.

Nothing there contradicts anything I've said.

You still go on about your magnetic neutralization, which is just anti-cogging scheme. Your buddy did a nice job with that test fixture. Can he use it to measure the difference in drive motor power at rated speed, no coils (or at least coils open circuit), just cores, with and without your magnetic neutralization, everything else being equal?

Has anything confirmed your claim of 2kW out/300w in?

Thanks for the update.
bi

[citfta]

Dave,

if you want to prove or disprove what bi has posted you can try the following experiment. Instead of an iron core you can use solid copper or aluminum. We know neither of those causes cogging. So if either of them cause the rotor to slow down and current consumption to go up then you will know that eddy currents and hysteresis is actually the cause.

Carroll

[bistander]

Dave,

if you want to prove or disprove what bi has posted you can try the following experiment. Instead of an iron core you can use solid copper or aluminum. We know neither of those causes cogging. So if either of them cause the rotor to slow down and current consumption to go up then you will know that eddy currents and hysteresis is actually the cause.

Carroll

Hi citfta,
Glad you join the discussion. And your proposed test is fine by me, but don't expect any hysteresis loss in a non-ferrous metal. Eddy currents should increase substantially over iron due to higher conductivity of Cu or Al for the same changing magnetic flux. However being non-ferrous, there may be, probably would be, much less flux, or lower flux density in the core.

Another method to demonstrate core loss vs cogging is to compare salient cores (like he has now) vs a flat smooth stator face (flat iron plate). The smooth plate would present no cogging, just a consistent braking torque.

Cogging: A term used to describe non-uniform angular velocity. It refers to rotation occurring in jerks or increments rather than smooth motion.

https://acim.nidec.com/motors/usmoto...ry-Terminology

bi

[OrionLightShip]

Cogging? That is not your problem here. You have three issues you should work toward fixing here.

1. HEAT ----- iron core heating from eddy currents can be reduced by using iron powder cores. Normal generators use laminated silicon (high resistance) steel cores of the correct thickness to work at 60 Hz. Aircraft dynamos operate at 400 Hz and thus require thinner laminations. Of course you would have to make your own cores using the least amount of binder and a hydraulic press. I suggest dry powder binders such as microcrystalline cellulose to avoid the wet mess. Otherwise, what is point of having a 2 minute generator?

2. HIGH INDUCTION ------ Not really a problem, but with more power generated comes higher opposing magnetic force due to Lenz. To counteract you need only use a bigger prime mover to reach the rpm you want, or employ your magnetic neutralization technique.

3. POWER MEASUREMENT ----- Volts and Amps mean nothing. You need REAL Power measured. Water calorimetry is the cheap and most accurate method but there are other means.

Cogging? Of course there is cogging at any speed. Magnets like iron. Who cares....the cogging force at speed is nothing compared to the generated force.

Just my unsolicited opinion of course.

Orion