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OverUnity Research > Motors > Miscellaneous Motors > Motor -Generator loop
2024-11-28, 13:47:57
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img  tinman
Re: Motor -Generator loop « Reply #25 on: 2013-06-11, 23:50:37 »
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Quote from: allcanadian on 2013-06-11, 19:12:27
@tinman
I would agree however four amps is not a "bit" four amps unloaded for that motor is absurd. As well there are things we can do to improve efficiency like using lapping compound to loosen tight bearings then washing them out and using a light synthetic oil so they run perfectly free. The brushes can be very loose and one half the width so they cover less than one half a segment. Then diodes, zener diodes, capacitors or NE2 neon's can be soldered across the commutator segments to solve the sparking issue completely. At this point timing is not dictated by brush sparking which is absurd, why not just solve the issue once and for all?.

I understand your point however a 50% decrease in an extremely large unloaded power draw is still excessive in my opinion. It is like saying that man threw a hand grenade at that person but thankfully it was only half a hand grenade so he was only one half dead.


AC
AC-did you watch my video's?.What you seguested is what i did. I washed out the bearings and put a couple of drops of machine oil in them. I also relieved the brush tention as much as i could. Using brushed that are 1/2 the width will only decrease output torque,as you have just reduced the on time by 50% for each rotor segment. Like i said before,an unloaded motor is not much good for anything,and a motor will always consume a set amount of power for a set amount of work being done.

I got my motor down to using under 6% of it's rated power at the rated voltage unloaded-feel free to show me how much you can get your brushed DC motor down from standard.
   
img  Allcanadian
Re: Motor -Generator loop « Reply #26 on: 2013-06-12, 01:40:57 »
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@tinman
Quote
AC-did you watch my video's?.What you seguested is what i did. I washed out the bearings and put a couple of drops of machine oil in them. I also relieved the brush tention as much as i could. Using brushed that are 1/2 the width will only decrease output torque,as you have just reduced the on time by 50% for each rotor segment. Like i said before,an unloaded motor is not much good for anything,and a motor will always consume a set amount of power for a set amount of work being done.

Yes I watched your video and I think you did one hell of a job in mating that generator to the motor O0. Basically what I'm saying is you have done everything right but I don't think you have taken it far enough. i'm trying to help and when I watched your video I knew within seconds that your bearings and your brushes are not where they could be. I know this because I have over 30 years of experience with these things. When the bearings are running free they make a tinny high pitched chatter yours do not they are dampened, when the brushes are free they make a very slight intermittent hissing noise and while you may have reduced the spring tension it is not near enough.

let me put it this way, turn the shaft with a slight amount of force and count how many revolutions your device makes. I will take a guess from what I could hear and say around three and one half revolutions max to dead stop. When I set up a motor like yours it will do 15 to 20 revolutions minimum. I guess the most relevant question is where do you think this idle current is being dissipated?.

AC


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Comprehend and Copy Nature... Viktor Schauberger

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img  tinman
Re: Motor -Generator loop « Reply #27 on: 2013-06-12, 11:01:50 »
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Quote from: allcanadian on 2013-06-12, 01:40:57
@tinman
Yes I watched your video and I think you did one hell of a job in mating that generator to the motor O0. Basically what I'm saying is you have done everything right but I don't think you have taken it far enough. i'm trying to help and when I watched your video I knew within seconds that your bearings and your brushes are not where they could be. I know this because I have over 30 years of experience with these things. When the bearings are running free they make a tinny high pitched chatter yours do not they are dampened, when the brushes are free they make a very slight intermittent hissing noise and while you may have reduced the spring tension it is not near enough.

let me put it this way, turn the shaft with a slight amount of force and count how many revolutions your device makes. I will take a guess from what I could hear and say around three and one half revolutions max to dead stop. When I set up a motor like yours it will do 15 to 20 revolutions minimum. I guess the most relevant question is where do you think this idle current is being dissipated?.

AC
The idle current is being dissipated in a few area's.First up in usage would be the armature windings them self,then we would also be dissipating some(very little) in the way of heat and friction in the brushes. A small amount would also be lost in bearing friction-but very little now.The current draw is a set amount with a brushed DC motor unloaded,and this amount is dependant on many thing's. The bearings are quite free,and will do for what we are looking to do with the motor. And as i stated before,there is no need to file down brushes,or have them that loose that we have arcing. It would be then pointlest to suppress that arcing with cap's and resistor's or neon's-as that is just another loss.Your brushes should always be firm enough that there is no arcing,and this will become apparent when the motor is placed under load-and then you will see that the filed down brushes wernt such a good idea.
I myself have been playing around with motors since i was 6 years old,so in 38 years you learn a thing or two at what makes them work better. But at the end of the day,it is the motor configuration that will determine how efficient you can make it.

I will say that this setup with this old motor and very old generator has supprised me quite a bit in regards to how efficient the two are together-in the way of P/in and P/out. I was thinking maybe around 55 to 60%,but as you will see in time,we have smashed that figure out of the ball park. It makes me wonder now how close we could actually get with an efficient motor and generator?.
   
img  ion
Re: Motor -Generator loop « Reply #28 on: 2013-06-12, 16:30:33 »
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It's turtles all the way down
Brush pressure is a function of required horsepower. Like any good electrical connection, it must be tight to eliminate arcing when high currents are being drawn.

You can loosen the brush pressure to improve idle current draw, but this will not be good once you restore the motor to it's rated capacity, and arcing will probably increase under heavy loads.

A lot of this stuff was worked out up to 100 years ago. Any good engineering level textbook on electro-dynamic machinery will cover brush pressure requirements.

Dynamotor theory and construction fairly well covers the subject.

If I thought there was merit in the motor/generator combo, I would opt for a brushless design. This would have more of a chance of being a self runner. It would need maglev bearings, the whole thing run in a vacuum with superconductive or other extremely low resistance windings.  Even so, I have my doubts if it could seriously approach unity.

But of what use would such a device be if it cannot deliver usable shaft horsepower and is easily overcome by the slightest friction or other loss?
« Last Edit: 2013-06-13, 12:51:49 by ION »


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img  Peterae
Re: Motor -Generator loop « Reply #29 on: 2013-06-13, 15:19:18 »

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Buy me some coffee
Don't worry EM i will bake you a file cake, or would you prefer some magnets for your motor  ;D
   
img  tinman
Re: Motor -Generator loop « Reply #30 on: 2013-06-14, 00:12:48 »
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Well i guess all the seriousness has gone from this thread ,so enough from me.

TinMan
   
img  EMdevices
Re: Motor -Generator loop « Reply #31 on: 2013-06-14, 04:01:11 »
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Sorry Tinman, just trying to lighten up the mood once in a while, don't be offended, your working on a fun project. :)

My suggestion for further efficiency improvement would be to lower the windage losses, which depend on velocity, so operate at a lower voltage, 12 instead of 24 and maybe also widen the air gap between the rotor and stator if you can.

Have you measured the brush contact resistance?  its proportional to tension, so if you remove the tension too much this resistance will be too high and your motor wont be so great under a heavy load when the current is high.

EM
   
img  GibbsHelmholtz
Re: Motor -Generator loop « Reply #32 on: 2013-06-14, 21:53:49 »
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Transformer obey conservation of energy.  I spent time trying to find the difference between motor and transformer.  Motor seems to obey conservation of charge since VxI related to backEMF x torque.  Most of the input energy is being supply to overcome BEMF, but like resonance, we can always add it at the time where BEMF is low. 
   
img  tinman
Re: Motor -Generator loop « Reply #33 on: 2013-06-15, 02:31:07 »
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Quote from: GibbsHelmholtz on 2013-06-14, 21:53:49
Transformer obey conservation of energy.  I spent time trying to find the difference between motor and transformer.  Motor seems to obey conservation of charge since VxI related to backEMF x torque.  Most of the input energy is being supply to overcome BEMF, but like resonance, we can always add it at the time where BEMF is low. 
Hi GibbsHelmholtz
It is actually the opposite that is true.The BackEMF is what reduces input current,not causes it. When an electric motor first start's,there is a large current draw-this is because there is little backEMF. As the motor speeds up,the current draw will go down because the backEMF increases with speed. The faster the motor spins,the more back EMF we get,and the less current we draw. BackEMF increases the apparent resistance in the winding's(or coils)and so our current draw drop's with the increased resistance. So the more backEMF we have,the greater the resistance,and the less current we draw.
If we supply a motor with 12 volt's,and we have !lets say! 8 volts backEMF,then the power across the coil will be 4 volts at a given current,not 12 volts at a given current. So the greater the backEMF,the lower the voltage across the coil at that given current.
   
img  GibbsHelmholtz
Re: Motor -Generator loop « Reply #34 on: 2013-06-15, 03:13:37 »
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Hi Tinman,

Yes, if we have 12V and the BEMF is 8volts.  The input is 4volts currrent x 12V while the actually energy the motor is recieve is 4V current.  We can compare input to out put by taking 12V x current vs BEMF x current as output.  In steady state condition assuming no friction, current supply = output current or torque in = torque out.  The only different is voltage supply vs BEMF output.  If BEMF is greater, output is more.  I thought per half we add current at zero crossing and extract current at peak.  My only concern is current at vary flux. 

   
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