Thane Heins Perepiteia.

[polarbreeze]

Thane has spoken more than once about induction motors having the property of requiring less and less power as they accelerate, so I don't think this is new.

Indeed he has, and he presents it as some kind of mystery that requires an unusual explanation. However, it's no mystery at all: it's absolutely standard behavior for an induction motor, as shown inÃ,  http://polk-burnett.apogee.net/pd/dmcs.asp . Hence my statement about "it's just a brake after all" - sorry, it may have sounded dismissive I guess but I simply mean that this issue is now resolved, which is a good step forward. BUT there is still an important issue remaining: the observation (by Thane/Luc and possibly others, although nobody else has said so yet) that there are differences in behaviour when different shaft materials are used (eg brass vs steel). This remains an open issue and I think (as do others including Aether) that this should now be the focus of attention.

PB

[bitbeam]

Hi All,

Forgive my cluelessness but does the tentative efficiency of 114% on Luc's latest test mean OU? 

Cheers,
Aaron

[polarbreeze]

Hi All,

Forgive my cluelessness but does the tentative efficiency of 114% on Luc's latest test mean OU?Ã, 

Cheers,
Aaron

It would BUT the operative word is "tentative". Luc's calculations do not take account of power factor (ie phase difference between current and voltage), which will have a huge impact, and his measure of input current has an uncertainty of about 25%. Until those major measurement issues are resolved, the efficiency is unknown.

PB

[bitbeam]

Hi PB,

Thanks for the info! These are exciting days! 

Aaron

[hoptoad]

However, it's no mystery at all: it's absolutely standard behavior for an induction motor, as shown in  http://polk-burnett.apogee.net/pd/dmcs.asp . Hence my statement about "it's just a brake after all" - sorry, it may have sounded dismissive I guess but I simply mean that this issue is now resolved, which is a good step forward. BUT there is still an important issue remaining: the observation (by Thane/Luc and possibly others, although nobody else has said so yet) that there are differences in behaviour when different shaft materials are used (eg brass vs steel). This remains an open issue and I think (as do others including Aether) that this should now be the focus of attention.
PB

It's standard behaviour for all motors. As the rotor of any motor increases rpm, it acts like a generator and produces its own magnetomotive force which induces a counter (back) emf in the drive windings. The final drive winding current is a vector of the source current minus the counter emf current.

I'll wager two pond lillies, that the "effect" is evident regardless of shaft materials, as it is related to the interaction of the external magnets and external coils, which are in a semi-open magnetic configuration in Vinces model. If Vinces rotor were non magnetic, and the coil is mounted on a non magnetic base, the effect will still occur, even though it would be a completely open magnetic system.

If the effect isn't evident with an induction motor, I'll still wager it will occur with a Universal motor, or a DC motor as a driver (which I've already documented in experiments. see link below)

http://www.totallyamped.net/adams        (page 10)

That's two pond lillies ........ anybody for a wager ? ...... KneeDeep

Cheers all.