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Historic Event Tonight?
RayB:
--- Quote from: Xiaou2 on January 15, 2010, 01:42:55 am --- As far as I have understood it.. Bemf is what causes ineffecient motors. Its also what
causes the current and voltages to reverse directions as it surges. The faster
the motor goes, the greater the bemf issue.
--- End quote ---
I've been reading up some more myself (don't ask me why) and BEMF is the natural "opposing force" effect that happens due to .. well, that's the laws of nature for ya (opposite reaction to every action type of thing).
So you're right, eliminating BEMF brings it more efficiency (as a motor), however.....
--- Quote from: Xiaou2 on January 15, 2010, 01:42:55 am --- This is vastly different than a typical generator, in that there is no harsh friction
and resistance to overcome... and yet, they still continue to gain energy.
You may also not realize, that they are using magnetic bearings too. This further
reduces friction loss, to almost nothing.
--- End quote ---
... now you're getting ahead of them. They have NOT demonstrated ANY power generation. They even said so themselves that they won't be demonstrating that until "later this month".
So so far all they can believably claim is getting closer to 100% efficiency. (Or maybe I should say closer to 99.99999% just to be within the laws of physics. ;-) ).
PS: Cheffo, how's your popcorn?
CheffoJeffo:
--- Quote from: RayB on January 15, 2010, 03:45:03 pm ---PS: Cheffo, how's your popcorn?
--- End quote ---
I'm out of popcorn, but the fridge is still well-stocked.
danny_galaga:
Sigh...
Here are the main reasons you actually WANT back EMF in a motor. First point to remember is that there is no such thing as a man made perpetual motion device. Remember this as i explain why you NEED back EMF.
By now everyone reading this thread will know that when a magnetic field passes through a conductor, an electrical current is produced. Conversely, if you run a current through a conductor, it can create an opposing force to a nearby magnetic field. Faraday loved this notion, because the functions are totally reversible, which strangely enough fitted in with his religious beliefs.
So, imagine we have a motor. We apply a current to its wound fields, they create an opposing force to the fixed fields. The details of construction are irrelevant. Say this motor is 12V, like the Steorn demo motors. The fields have quite a low resistance. So when you apply the voltage to the fields, there is a high current draw. Lets say the fields have 1 Ohm resistance. Voltage /current x resistance. You have 12 amps of current.
But hang on, lets go back. Remember that when a magnetic field passes through a conductor, an electrical current is produced. It doesn't matter that you have just applied current to create a motor. Do you not still have a conductor passing through a magnetic field? Yes, you do. Even as the device is functioning as a motor, it is generating a current. This is back electro motive force. So what of it? Well, naturally the back EMF is less than the applied voltage. But lets have a look at what happens (using ball park figures for demonstration purposes).
Situation 1) Voltage is applied to motor. At rest it is infinitely slow. V=12,R=1, A=12
Situation 2) Motor is now spinning at say 500 rpm. It is producing some back EMF. Say 1V. So now total voltage applied is 11V (12V-1V). So now V=11, R=1, A=11.
Situation 3) Motor is now spinning at 1000 rpm. Back EMF is now 2V. So now V=10,R=1,A=10
Situation 4) Obviously this is an infinitely variable scale. Lets just skip to 10,000 RPM. Back EMF is now say 11.5V (in real life nothing is linear, there is always some sort of curve) So now V=0.5,R=1,A=0.5
edit: i should point out that situations 1 to 4 normally happen in a split second. Very desirable in a lot of cases. For instance, at rest a car starter can draw up to say 500 AMPS. When it is spinning, with no load, maybe 20 AMPS. With a load, say 150 AMPS.
This is both what an electric motor does, and what we desire. Because there is no such thing as a man made perpetual motion machine. Why do we desire this? Because the current draw is directly proportion to the torque produced. Therefore, Our little electric motor has full torque at rest, and least torque at high RPM. This is exactly what is needed in most cases. For example, an electric car, an electric drill. A starter motor for a petrol engine.
A motor is a motor is a motor. They are there to fulfill real mechanical needs. Most of our needs for electrical motors demand torque. Not all mind you. ceiling fans have very little torque. They use induction motors, utilising the single phase a/c mains current instead of a commutator or speed controller. Because of this, they have very little torque, since there is only a narrow range of speeds the motor is designed to work in.
I would bet you a dollar that when they applied a load to that 'regular' motor in the video, they probably used say two fingers on the shaft. And i bet that for the 'perpetual motion machine' (lets call a spade a spade) they could have put a fingertip on top of the shaft for the same speed reduction. That's how little torque that thing probably has. Therefore it takes very little to keep it going. But what's the point of that? Take away the power and it will take longer to stop than a regular motor. Maybe even magnatudes longer. Have they invented the ultimate 'it takes a long time to stop' machine? No, my 200kg flywheel would trump it...
danny_galaga:
Lesson in basic induction part 2 (yes i know, there wasn't really a part 1)
There is a place for low torque devices that use the properties of electromagnetic induction. Lets do a simple thought experiment. Imagine you have a plastic cup on a shaft supported by bearings. inside the cup is a steel wheel that fits closely. It is also on a supported shaft. The steel wheel is mildly magnetic. If you spin the wheel, will its magnetic force make the plastic cup turn?
Now, suppose the cup is made of aluminium, not plastic. Will the magnetic force of the steel wheel make the aluminium cup turn? The amswer is yes!
How come? Aluminium isn't magnetic, any more than plastic. But, aluminium is a conductor. This is important. remember, if a magnetic field passes through a conductor, a current is produced. So a current is produced in the aluminium cup. This conductor however is not a wire, guiding the current anywhere. The current stays within the cup. You could say it is a dead short. Current is flowing however. What happens to a conductor when current flows through it? It becomes magnetic. Now both the steel wheel and the aluminium cup attract each other. The cup spins.
This is the basis for the humble speedometer. Or was until electronic ones started to appear in the 1990's.
That's the sort of use Steorns 'invention' can be put to. A speedometer has very little back EMF...
RayB:
Can't let this thread die off without a proper wrap-up. Well here it was, finally after much talk and delay, climactic "proof" of over-unity (more energy out than in)!!
Well... not really. That's what the dude says, but once again, no proof shown unless you want to take him at his word:
Part 1 - blah blah blah
Part 2 - blah blah 327% blah
No voltmeter showing a battery or capacitor being charged up with the "excess energy". No lights being powered... nothing but a squiggly line on an oscilloscope that the layperson has to take at his word is "excess energy".
The key to all this is at 8:30. They sell developer licenses for 419euros. Lets say they got even just 1000 hobbyists to buy licenses so they can play around with this. That's half a million USD. I could live pretty good off that. You? And lets not forget that the license comes with a Non Disclosure Agreement so licensoees can't publicly say it doesnt work.
I guess we'll have to wait and see (again) if their licensees break that agreement or not.
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