Rotating Magnetic Field's and Inductors.

[tinman]

Tinman,

Yes, I was referring to the FG driven tests.  Do you know for certain to which polarity you are synch'ed (i.e., which polarity and position at turn on)?

Having looked at your waveforms a bit more, the rotor inertia/magnet interaction with the drive coil appears to increase the effective inductance of the coil.  Coil current rises more slowly due to the effective inductance increase, hence less input current.

I am somewhat reminded of an Orbo...

PW

If the magnets were increasing the effective inductance of the coil,why dose this increase not happen when the magnet(either pole) on the rotor is stationary in front of the coil?.

I think the rotor magnets are inducing an EMF across the coil,and it is this EMF that is the cause of the reduce P/in,as the battery now dose not have to supply that bit of energy to create that EMF that already exist. If we look at the scope shot,we can see that induced EMF from the rotor magnets has the correct polarity to that of what the battery will supply during switch on.

I will have to see if i can get this new coil to sink with the pulsed inductor,and i think i have a way to make the job easy

I am guessing that i am synch'ed with the center of the two magnets,as they are alternating fields-N S N S N S N S


Brad

[tinman]

If the magnets were increasing the effective inductance of the coil,why dose this increase not happen when the magnet(either pole) on the rotor is stationary in front of the coil?.

I think the rotor magnets are inducing an EMF across the coil,and it is this EMF that is the cause of the reduce P/in,as the battery now dose not have to supply that bit of energy to create that EMF that already exist. If we look at the scope shot,we can see that induced EMF from the rotor magnets has the correct polarity to that of what the battery will supply during switch on.

I will have to see if i can get this new coil to sink with the pulsed inductor,and i think i have a way to make the job easy

I am guessing that i am synch'ed with the center of the two magnets,as they are alternating fields-N S N S N S N S


Brad

Thinking about that some more--that will not work out,as the field from the coil will want to pull on the rotor magnets in the opposite direction 50% of the time.
UMmm-will have to do this strobe setup,so as i can see what is going on here.
Im now thinking that in order for the rotor to spin at all,it must be synch'ed to every second set of magnets 

Brad

[picowatt]

If the magnets were increasing the effective inductance of the coil,why dose this increase not happen when the magnet(either pole) on the rotor is stationary in front of the coil?.

My guess would be rotor inertia...

In a rather mechanical analog of an inductor, energy is being stored and recovered via rotor inertia.  Work is being done to accelerate the rotor, with a portion of that recovered.  There does, however, have to be a net gain of rotor energy or the system would come to a stop, so only a portion of what is stored is being recovered.  A better understanding might be had if you were to produce an accurate timing diagram detailing rotor accel and decel and rotor/magnet position versus coil on time.  A degree wheel, a couple optocouplers, a divide by 90 and a 4046 PLL come to mind...   

I think the rotor magnets are inducing an EMF across the coil,and it is this EMF that is the cause of the reduce P/in,as the battery now dose not have to supply that bit of energy to create that EMF that already exist. If we look at the scope shot,we can see that induced EMF from the rotor magnets has the correct polarity to that of what the battery will supply during switch on.

I considered this, as you mentioned it before.  But when is the work being done to accelerate the rotor?  I assume you sync up with the help of mister hand, but unless the rotor slows over time, it must be accelerated by the coil.

Although the portion of the cycle where the sine wave is visible is unloaded and only producing a voltage in the coil, it seems logical to assume that the rotor must be slowing during that time due to the loading of circuit leakage, eddy current production, bearing friction and windage.

So, either the rotor accelerates during the coil on time with some energy recovered during flyback, or, some energy is recovered during the coil on time and the rotor is being accelerated during flyback.   

I will have to see if i can get this new coil to sink with the pulsed inductor,and i think i have a way to make the job easy

I am guessing that i am synch'ed with the center of the two magnets,as they are alternating fields-N S N S N S N S

Brad

I'd rather see some stroboscopic evidence of the rotor position and magnet polarity at turn on using the original setup.

(Added:  And, of course, what polarity your coil produces when turned on...)

PW

(edited second to last sentence...)

[picowatt]

Thinking about that some more--that will not work out,as the field from the coil will want to pull on the rotor magnets in the opposite direction 50% of the time.
UMmm-will have to do this strobe setup,so as i can see what is going on here.
Im now thinking that in order for the rotor to spin at all,it must be synch'ed to every second set of magnets 

Brad

I have been assuming that the coil is turned on every 90 degrees of rotation (every other magnet).  Do you know what the RPM versus trigger frequency is?

PW

[picowatt]

I think the rotor magnets are inducing an EMF across the coil,and it is this EMF that is the cause of the reduce P/in,as the battery now dose not have to supply that bit of energy to create that EMF that already exist. If we look at the scope shot,we can see that induced EMF from the rotor magnets has the correct polarity to that of what the battery will supply during switch on.

Tinman,

This may be true.  It could be that deceleration and energy recovery happens at/during coil turn on, with acceleration occurring during the flyback.  Either way, the rotor's inertia acts like a mechanical "inductor" magnetically coupled to the coil.

If you would strobe the rotor and check your coil's polarity, we should be able to come up with a few more answers.

PW