Thread: Perpetual Motion

Is this just marketing hype for 'dynamic braking' where the DC motor is used as a generator when braking or when going down hill ?
This concept has been around ever since the DC motor was invented and is used on trains, trams, Prius cars and even cigarette machines (if they still exist) !
Perpetual motion (ha ha), not in my (or anyone elses) lifetime. Though Joh was pretty taken with the hydrogen car that ran on water, so I guess in Qld anythings possible !

Deano

My favourite perpetual motion device:

[ame="http://en.wikipedia.org/wiki/Buttered_cat_paradox"]Buttered cat paradox - Wikipedia, the free encyclopedia[/ame]

Originally Posted by DeanoH

Is this just marketing hype for 'dynamic braking' where the DC motor is used as a generator when braking or when going down hill ?
This concept has been around ever since the DC motor was invented and is used on trains, trams, Prius cars and even cigarette machines (if they still exist) !
Perpetual motion (ha ha), not in my (or anyone elses) lifetime. Though Joh was pretty taken with the hydrogen car that ran on water, so I guess in Qld anythings possible !

Deano

its a more advanced form of regen braking I've heard stories of it a few years ago but they had it marketed something long the lines of capturing the back EMF from when the poles go over center in their fields I wrote it off then as a perpetual motion idea but someone showed me some trickery on a solenoid with a blocking diode (changing the diode out for some other bits) the first firing of the solenoid worked as per normal and every subsequent shot was a measurable amount stronger (one off, the first shot produced say 10 units of effort and all subsequent shots produced 11)


hypothetically
If that bit of trickery has been put into use into a multi winding motor what hes offering makes sense and is not perpetual motion just reusing the waste energy.

It all sounds like BS to me Dave.
What you're saying about solenoid/relay coils is correct. One of the 'tricks of the trade' in pre solid state electronics when relays etc were king was to reverse bias a diode across a winding. When the magnetic field collapsed in the winding the resultant current was in the opposite direction to the original current flow which re-energised the magnetic circuit (via the diode), but in the opposite direction. The end result was that the relay/solenoid stayed operated longer. Effectively the device became 'slow release'. Very useful in electronic design.
This example shows how to capture the energy from a collapsing magnetic field (used in creating the field in the first place) and to use it to hold the device operated after the original voltage has been disconnected. This principle of using voltage from a collapsing magnetic field is exactly how a cars ignition coil works. But note, power was used to create this magnetic field in the first place so there is no net gain.
As for the electric motor analogy, the magnetic field needs to be there all the time for the motor to work. It is not switched on and off like a solenoid/relay so it isn't the same scenario.
Capturing the energy from a collapsing magnetic field and re-using it is good design but no big deal.
It may be possible to create a more efficient magnetic circuit but there's no such thing as a free lunch, that is of course until the marketing people get hold of it.

Deano

as I understand the principal behind the concept..

from the solenoid replacing the solenoid's diode with some other dohickery lets you capture the back spike from the solenoid then throw it in with the next application of power. No, your not getting something for nothing, you're just wasting a little less.

with an electric motor as the individual poles of the motor come past their corresponding fields you get the same effect in a brushed motor you dont notice it because the armatures windings arent connected to anything. (Im not sure if you could even try to pull this off with a brushless motor. ) I'd have thought that with a second set of off "power" brushes you'd be able to pull out the off spike juice and then somehow feed that back in.. again you'd have to put the energy in in the first place to get everything turning and you'd never get all the power back from losses but you might be able get something.. of course, the effert involved in setting it up (read complexity and expense) would probably not come close to what you might get back out and any effeciency gain would probably also be less than setting up for brushless.

Originally Posted by Blknight.aus

......replacing the solenoid's diode with some other dohickery lets you capture the back spike from the solenoid then throw it in with the next application of power. No, your not getting something for nothing, you're just wasting a little less...................

Can't argue with the concept.
When you consider the main power requirement to operate a relay/solenoid is its actual operation as oposed to holding it operated; if you could capture the energy from a devices collapsing field in say a capacitor and then use the discharge pulse energy from this capacitor to 'boost' a solenoids re-operation then there would be a considerable saving in energy used and hence the dimensioning of its power supply.
Only thing is I can't think of a scenario where there are banks of solenoids continually operating/releasing where this concept could be used.

Originally Posted by Blknight.aus

.....................with an electric motor as the individual poles of the motor come past their corresponding fields you get the same effect in a brushed motor you dont notice it because the armatures windings arent connected to anything. (Im not sure if you could even try to pull this off with a brushless motor. ) I'd have thought that with a second set of off "power" brushes you'd be able to pull out the off spike juice and then somehow feed that back in..............

Multiple windings on the rotor all magnetically coupled with each other. When one winding passes the brushes its field collapses causing the other windings to become pre-energised before the application of power through the brushes, effectively kick starting the next winding(s) to be energised. ie. effective use of the energy stored in the collapsing magnetic field. Or I think so anyway. Putting a load on the winding(s) with collapsing fields in order to store the collapsing magnetic field energy as an electrical charge in say a capacitor would be the same as 'dynamic braking' and would be taking power from the system. Again, I think. It's 40 years since I did the theorey for all this but the underlying principles haven't changed, just the materials and applications.

I've no doubt this blokes got an efficient setup, and with todays cheap electronics and quality materials it should be. I guess he has to separate his product from the herd and snake oil is the tried and proven way.

Deano