Reactive power - Reactive Generator research from GotoLuc - discussion thread

[gotoluc]

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]

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]

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]

.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]

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