Confirming the Delayed Lenz Effect

[Farmhand]

I agree Milehigh, and I can actually do that experiment and I will. I know it will be different because I can see that happen when I change the timing, which means the coil is energized while away from the rotor magnet.  The current waveform changes dramatically which is why my current shot's look different at times, it's because of the timing of the pulses in relation to the magnet position.

For the test I can run the circuit with a fixed pulse width driving the rotor and scope the currents, then I can do either of two things. I can swing the timing right out of the way or I can stop the motor and remove the rotor and either take out the magnets and spin the rotor with another motor to get the timing or I can use a circuit I have to trigger the the CD4047 chip at the same frequency as the motor coils were firing when running, that way the coils will be switching the same with the same pulse width and but with no rotor magnets. If I make a 1 minute video clip I can show the waveform change in real time when I change the timing. Piece of cake. That was obvious when the experiments are done and notice is taken. 

When the motor is running faster at some times it has a lot less peak current through the coils than when running slower.

Rather than post more shots I'll make a 1 or 2 minute video clip to show it.

Cheers

Oh and for future reference my rotor weighs in at 435 grams which is almost 1 lb. Might be useful for an idea on the acceleration. I can now spin the rotor at 1600 rpm with 175 mA of current from the 12 volt battery.

P.S. Milehigh, thinking of the test made me wonder how the motor might run if I were to run the motor up to a certain speed/frequency then switch from the trigger signal to a steady frequency signal to keep it spinning at the same rate, make it "fully synchronous". hehehe Would be a fun test as well.

..

[Farmhand]

Here's a Video Clip of the magnet proximity (coils driving the rotor more) causing the coil current to reduce, the further away the magnet is when he coil is energized and therefore
the coils are driving the rotor less the "more" the current in the coils. The closer the magnet is to the coil core when the coil is energized the less current goes through the coils.

I think this is what you mean Milehigh ? In a way.

Pulse Timing and Coil Currents
http://www.youtube.com/watch?v=0whkutQ7mNQ

..

[synchro1]

@MileHigh,

Here's a quote from you to Tinselkoala after he reported a rise in input with no magnet spinning with his sine wave motor:


"I think the basic dynamics are that the higher frequency you go the higher power you have to pump into the coil."


How does your current theory explaining the opposite effect to Farmhand influence your past position?

[MileHigh]

Synchro1:

That's a great question.  The thing to keep in mind that in many cases the properties of a circuit are frequency dependent.  For example an ordinary capacitor will change how it responds in frequency.  A low and high frequencies a capacitor looks like a capacitor and passes the signal.  But at very high frequencies the capacitor will act like an inductor and block the very high frequency signal.

So you can imagine a scenario like the following:  If you run a typical pulse motor at low to medium frequency, you may see decreasing input power consumption as the speed increases because of the "voltage stealing" effect from power being exported to the rotor.  (That's what they mistakenly call "the witch" on you know which threads on EF.)  But as you run at higher frequencies the air friction starts to become very significant and then the power consumption will start to go up.  I'm not just sticking these two ideas together for convenience, this is a very real property that you see in many places.  Another example is a typical transformer.  At low to medium input frequencies the transformer will work properly.  But at very high input frequencies, the input capacitance of the transformer primary will effectively short out the input signal and the transformer output is near zero.  The minuscule input capacitance will prevent any current from flowing into the primary windings so the transformer can't work, only if the input signal is at a very very high frequency that you normally wouldn't use anyways.

Tech link about transformers and frequency responses:
http://www.vias.org/eltransformers/lee_electronic_transformers_06_09.html

Again, these are basic principles that would have to be investigated on a case-by-cases basis. 

MileHigh

[TinselKoala]

Also, don't forget that my magnet spinner is working on a 50 percent, symmetrical duty cycle and is properly a "synchronous" motor, a special case of pulse motors. No doubt proper pulse shaping as to width and amplitude could optimize the current/rpm relationship -- as Farmhand's results indicate.