Storing Cookies (See : http://ec.europa.eu/ipg/basics/legal/cookies/index_en.htm ) help us to bring you our services at overunity.com . If you use this website and our services you declare yourself okay with using cookies .More Infos here:
https://overunity.com/5553/privacy-policy/
If you do not agree with storing cookies, please LEAVE this website now. From the 25th of May 2018, every existing user has to accept the GDPR agreement at first login. If a user is unwilling to accept the GDPR, he should email us and request to erase his account. Many thanks for your understanding

User Menu

Custom Search

Author Topic: Reactive power - Reactive Generator research from GotoLuc - discussion thread  (Read 362093 times)

gotoluc

  • elite_member
  • Hero Member
  • ******
  • Posts: 3096
Hi poynt or anyone who know the poynt way of AC scope power calculations.

Please tell me what the power used from the source (grid) in watts from the scope shots below. Both are the same just one has 15 samples instead of 3.

The CSR is 0.1 Ohm 5% with both probe grounds on one grid side of CSR, channel 2 on circuit side of CSR and channel 1 on other grid side and is 100x probe with scope menu at 100x. Chanel 2 probe is set at 1x and scope menu is set at 10x with Inverted selected.

Thank you for your time.

Luc

gotoluc

  • elite_member
  • Hero Member
  • ******
  • Posts: 3096
I've been following this thread with interest for a while but I haven't felt that I had anything to contribute. Just lurking and learning; I'm dealing with reactive power issues in my wireless power / induction heating systems and trying to learn what I've missed.

I dug into my motor box and came up with a pair of interesting little motors that might enable me to do some experimentation. See the image below. These are antique Delco DC shunt motors. They are constructed just like modern DC "can" motors: wound armature, commutator, brushes, but in place of the magnets in the can motor, these have field coils. The two coils are connected in series and brought out to a pair of wires. The brushes are brought out in another pair of wires. There's no cap or other circuitry, so wiring options are unlimited and easy to implement. It has been some time since I've run these motors, but this is what I remember: The motors run well with separate DC supplies to the field coils and the armature, and there is an interesting relationship between output torque and the voltages one supplies to the two parts of the motor. The motors will also run from a single supply, IIRC, with the field coils in series with the armature brushes. Or maybe in parallel or both, I can't recall at the moment.

Since "mo-gens" are kind of a "hot" topic at the moment, I was thinking about mounting the pair on a board, coupled shaft-to-shaft, with one as "prime mover" and the other as generator. Any suggestions as to hookups, capacitor placement, rectification, etc. so I can start experimenting for myself?

Very interesting motors you have there TK

the only thing is, you mentioned they are DC... not a problem for prime mover and maybe better then using an AC motor as far as power calculations go. The problem would be the gen side. I think the circuit needs AC since the basic ingredient is a series capacitor and I don't know how you could get the circuit to work with DC?

Maybe have a look at the pdf Hob has shared for a circuit you can test.

Link: https://sites.google.com/site/nilrehob/home/documents

Also, if you don't mind have a look at my post above and tell me what you come up with.

Thanks

Luc

tinman

  • Hero Member
  • *****
  • Posts: 5365
A good brief review of an AC generator.

http://www.auroragenerators.com/resources/articles/how-stuff-works/29-generator-fundamentals
http://armymunitions.tpub.com/Mm07047/Mm070470067.htm
Brad,

Not shown, but the caps in these generators you and Luc are using are for filtering a rectified AC (produced from a residual magnetic field) in order to produce a crude DC field coil supply?
\
Hi Darren

These one's work a little different than that. These one's have 2 PM's on the rotor that excite the exciter field. The two rotor coil's have a diode on each,so as to produce a south field on one half of the rotor,and a north field on the other. By changing the cap value,we can raise or lower the RPM to get our 240 volt output. If we keep the same RPM,we can raise or lower the voltage output by changing the cap value. For example,i change the cap with a 200uf cap(just to see what happened),and the gen would produce 230 volts at 21htz-around 1260RPM.

In regards to load's on the output.
I found that a 70 ohm load was about as high as i could go befor the prime mover started to require more power. So it seems the heaver the load,the less power required by the prime mover. If i remove the load from the MOT output,my generator bog's down that much that the prime mover cant drive it. Seems to be reverse to what you think it would be.

Some figures so far.
P/in with all gen outputs open is 52 watts.
P/in with exciter circuit and inductive circuit hooked up is 55 watt's.
exciter circuit is consuming 4.1 watt's
55 watts minus 4.1 watts=50.9 watt's.
So some how we have 1.1 watts of !accounted for power! higher than we do with the generator open?.
This ofcourse is only the case if the watt meter and both DMM's are 100% accurate.My DMM's would be very close at this frequency,but im not sure how the watt meter is reacting with the PWM.

tinman

  • Hero Member
  • *****
  • Posts: 5365
.99,

The brushless cap regulated units Luc and Tinman are using are not covered in that doc.  The caps in their units actually regulate the voltage by resonating with and varying the phase angles of the exciter windings as load conditions vary.  Some units resonate the exciter at the fundamental, many newer units do so at the third harmonic.

I believe the cap regulated units draw a bit more from the prime mover under no load than required for a given output voltage because the exciter phase must be prepared for application of reactive loads, particularly for motor starting.  Severe loading or certain highly reactive loads applied to a cap regulated unit can cause the exciter phase angles to exceed a maximum and cause the exciter current to collapse with subsequent collapse of the field output . 

The reduction of this no load exciter "excess" is what I suspect is related to the reduction in prime mover loading observed with certain reactive loads applied.  Most reactive loads are inductive, so the gens are set under no load conditions to more ideally operate when inductively loaded. 

Please note that I am in no way an expert on induction motors or generators.  But there is a glimmer of an explanation in the above somewhere.

It would be interesting if the experimenters could find the schematics for their respective gen models.

PW.     
PW-you hit the nail on the head.
In my test so far,no resistive  load will reduce the P/in required to drive the generator. Only an inductive load(so far) has this effect of reducing the P/in required to drive the generator.
I am yet to try a capacitive only load on the output. As the exciter circuit is just a tank circuit,i could place a cap of a certain value on the gen output,and then make that a second tank circuit.If i can offset the phase angle between the two tank's,then we may get some interesting results.

gotoluc

  • elite_member
  • Hero Member
  • ******
  • Posts: 3096
Hi everyone,

I uploaded a video which is unlisted. I did this not to confuse other researcher from other sites and so on since this video is related to the discussion going on here.

So here is a test a la TinMan of my best score yet

Link to video: http://www.youtube.com/watch?v=CyoT9I3_93w&feature=youtu.be

I may also have another interesting thing in the works and will share when I confirm the ideal values for maximum output.

Stay tuned

Luc

poynt99

  • TPU-Elite
  • Hero Member
  • *******
  • Posts: 3582
Hi poynt or anyone who know the poynt way of AC scope power calculations.

Please tell me what the power used from the source (grid) in watts from the scope shots below. Both are the same just one has 15 samples instead of 3.

The CSR is 0.1 Ohm 5% with both probe grounds on one grid side of CSR, channel 2 on circuit side of CSR and channel 1 on other grid side and is 100x probe with scope menu at 100x. Chanel 2 probe is set at 1x and scope menu is set at 10x with Inverted selected.

Thank you for your time.

Luc

Luc,

I would say that the second shot with more cycles is the better bet. Note, you need about 10 cycles of the MATH trace, not the voltage or current traces to get an accurate power computation.

I am finding that the GRID power measurement does not seem reliable in my setup at least. I am using a 10uF cap, and 10 Ohm resistor. Depending on which CSR I use, I get a different GRID power.

For example, with the 0.1 Ohm CSR, I get a GRID power of about +3.8W (your probe config. and not inverted btw). With my non-inductive 0.25 Ohm CSR, I get a GRID power of about +2.5W. The power in the 10 Ohm measures to about 1.5W using a DMM, and compared against a DC control it is close at about 1.3W. So the DMM voltage (4.3VAC) over the resistor value is close, but probably coming out a little high (3.6VAC is more correct).

My wave forms look quite close to what you posted above.

Unfortunately thus far with my setup I can not get the negative MEAN GRID power you have with a couple of your tests. Technically it is supposed to be positive anyway (since I have not inverted CH2), but I was hoping to be able to get close to your -3.15W.

More work ahead to see if I can figure out why it is behaving more or less the way it is supposed to, LOL. btw, you may have noticed that I still have 1W or so unaccounted for. I was able to measure about 0.6W being dissipated in the 10uF cap, but still short.

btw, I tried your little trick of using a x1 voltage probe as a "current probe" while setting up the channel to measure current directly with the proper scaling. Seems to work ok. ;) Sorry for giving you a hard time about that.

gotoluc

  • elite_member
  • Hero Member
  • ******
  • Posts: 3096
Luc,

I would say that the second shot with more cycles is the better bet. Note, you need about 10 cycles of the MATH trace, not the voltage or current traces to get an accurate power computation.

I am finding that the GRID power measurement does not seem reliable in my setup at least. I am using a 10uF cap, and 10 Ohm resistor. Depending on which CSR I use, I get a different GRID power.

For example, with the 0.1 Ohm CSR, I get a GRID power of about +3.8W (your probe config. and not inverted btw). With my non-inductive 0.25 Ohm CSR, I get a GRID power of about +2.5W. The power in the 10 Ohm measures to about 1.5W using a DMM, and compared against a DC control it is close at about 1.3W. So the DMM voltage (4.3VAC) over the resistor value is close, but probably coming out a little high (3.6VAC is more correct).

My wave forms look quite close to what you posted above.

Unfortunately thus far with my setup I can not get the negative MEAN GRID power you have with a couple of your tests. Technically it is supposed to be positive anyway (since I have not inverted CH2), but I was hoping to be able to get close to your -3.15W.

More work ahead to see if I can figure out why it is behaving more or less the way it is supposed to, LOL. btw, you may have noticed that I still have 1W or so unaccounted for. I was able to measure about 0.6W being dissipated in the 10uF cap, but still short.

btw, I tried your little trick of using a x1 voltage probe as a "current probe" while setting up the channel to measure current directly with the proper scaling. Seems to work ok. ;) Sorry for giving you a hard time about that.

Okay, thanks for the update!

but I'm getting a little confused... why are you measuring without channel 2 Inversion when you said without doing that I'm getting the wrong readings?

And can you please tell me what the power is on the scope shots I provided above with channel 2 Inverted since I no longer know how to read a scope.

Thanks for your time

Luc

poynt99

  • TPU-Elite
  • Hero Member
  • *******
  • Posts: 3582
Okay, thanks for the update!

but I'm getting a little confused... why are you measuring without channel 2 Inversion when you said without doing that I'm getting the wrong readings?
The first task is to try to replicate your results the way YOU produced them. So I am trying the measurements the same way you are doing them. If and when I get the same or similar results (i.e. a negative MEAN GRID power), then I can move on.

Quote
And can you please tell me what the power is on the scope shots I provided you with above with channel 2 Inverted since I no longer know how to read a scope.
What do you mean you no longer know how to read it. It is the MEAN value as before. I see +194mW.

gotoluc

  • elite_member
  • Hero Member
  • ******
  • Posts: 3096
Unfortunately thus far with my setup I can not get the negative MEAN GRID power you have with a couple of your tests. Technically it is supposed to be positive anyway (since I have not inverted CH2), but I was hoping to be able to get close to your -3.15W.

If you Isolate your scope from grid then use 240vac and you should get a negative means

Luc

poynt99

  • TPU-Elite
  • Hero Member
  • *******
  • Posts: 3582
If you Isolate your scope from grid then use 240vac and you should get a negative means

Luc

I guess I can try that, but you were getting it on a single phase. And I did isolate the gnd on my scope. Do you mean transformer isolation as well?

gotoluc

  • elite_member
  • Hero Member
  • ******
  • Posts: 3096
The first task is to try to replicate your results the way YOU produced them. So I am trying the measurements the same way you are doing them. If and when I get the same or similar results (i.e. a negative MEAN GRID power), then I can move on.

Okay, I understand. I posted above how to get there but you'll need a 100x probe to display the 240v


What do you mean you no longer know how to read it. It is the MEAN value as before. I see +194mW.

Okay, so you're sure by using the Inverted probe that the power I'm using from the grid is 194mW. If so, we have a big problem now!  because the load has 8 watts more than the input.

What to do now?

Luc

gotoluc

  • elite_member
  • Hero Member
  • ******
  • Posts: 3096
I guess I can try that, but you were getting it on a single phase. And I did isolate the gnd on my scope. Do you mean transformer isolation as well?

I have a 1 to 1 Isolation transformer on my scope. You'll need that for sure since the scope grounds will be connected to the other hot side of your 120v main.

Luc

gotoluc

  • elite_member
  • Hero Member
  • ******
  • Posts: 3096
I guess I can try that, but you were getting it on a single phase. And I did isolate the gnd on my scope. Do you mean transformer isolation as well?

You can also try 15uf or 20uf and see what you get on 120v alone.

Luc

poynt99

  • TPU-Elite
  • Hero Member
  • *******
  • Posts: 3582
Okay, I understand. I posted above how to get there but you'll need a 100x probe to display the 240v
Not a problem, in fact I have a high voltage differential probe that I can use for that.

Quote
Okay, so you're sure by using the Inverted probe that the power I'm using from the grid is 194mW. If so we have a big problem because the load has 8 watts more than the input.

What to do now?

Luc
I am pretty sure the scope is correctly computing what you are giving it. I don't know however how exactly you have things set up inside the scope. Is the scope getting a clean measurement, and are there any issues with grounding? (rhetorical questions). Transformer isolation may be in order here, as I see a small voltage across the CSR even when the HOT is disconnected.

You measured the load with your DMM correct? It worries me a bit because of what I saw and the fact that the wave form it is reading is far from sinusoidal, and far from pure 60Hz.

Also, as I said at the present moment I am not very confident in the GRID power measurement itself.

Where to go from here? When things seem too good to be true in terms of power measurements, they usually are. Which means we should be finding a way to double check our findings. My feeling is that you might have a large reactance somewhere that is skewing the power measurement. You are getting almost zero Grid power, yet you are dissipating significant power in your load.

I don't know Luc. Send me your parts, and I'll send you mine?

poynt99

  • TPU-Elite
  • Hero Member
  • *******
  • Posts: 3582
I'll have to bring in the isolation transformer from work. Do you also have the gnd isolated? I ask because even isolation transformers can carry the earth ground across.