Serious HES derivative project proposal

[bistander]

And in this video, a three-phase current supplied from a frequency converter, unfiltered from higher harmonics.
See the difference...
https://youtu.be/jww9Hyhh9G0
p.s. Very bad camera. The good camera in my phone broke.  It would be much better.

Hi kolbacict,
I see the difference. Good job. Another beer for you.
bi

[citfta]

Hi guys,


Regarding using a VFD powered by DC we need to see what the actual signal looks like.  Here is a video I did and posted in my thread about a moving virtual magnetic field.


https://rumble.com/v1hh4ux-driving-an-alternator-with-rc-speed-controller.html


If you watch that video you will see that my RC speed controller worked great to drive an alternator as a motor.  BUT the pseudo sine wave is actually generated by PWM modulation and did not work well for induction.  So depending on whether or not the output is actually a sine wave a VDF may or may not be a good idea.


Great work guys.  I am following along but will only comment if I feel I have something useful to add.


Carroll

[bistander]

Hi guys,


Regarding using a VFD powered by DC we need to see what the actual signal looks like.  Here is a video I did and posted in my thread about a moving virtual magnetic field.


https://rumble.com/v1hh4ux-driving-an-alternator-with-rc-speed-controller.html


If you watch that video you will see that my RC speed controller worked great to drive an alternator as a motor.  BUT the pseudo sine wave is actually generated by PWM modulation and did not work well for induction.  So depending on whether or not the output is actually a sine wave a VDF may or may not be a good idea.


Great work guys.  I am following along but will only comment if I feel I have something useful to add.


Carroll

Hi citfta,
Nice demo. Thanks. Of course VFDs use PWM to synthesize sinusoidal waveforms. The voltage will always appear as pulses. But the current is considerably smoother, especially if filters are used or the coils are of high enough inductance. kolbacict's videos show the effects of filters.

The other distinction noted is the RC motor driver has no buss capacitor, that I am aware. The larger VFDs have considerable capacitance directly on or adjacent to the switch bridge. That could be a factor.

What signal was displaying on the scope?
And when you say it didn't work well for induction, what do you mean, or what did you measure to arrive at that conclusion? As in running the former alternator as an induction motor, perhaps?
bi

[citfta]

Hello Bi,


The signal on the scope was the signal going to one of the 3 legs of the y connected alternator.  As you could see it worked pretty well as a motor.  But when I stopped the rotor to try and draw current from the slip rings as I had done earlier the output from the slip rings was pretty low.  So I concluded that was not a good signal for inducing power into the locked rotor from a virtual rotating magnetic field.


Take care,
Carroll

[bistander]

Hello Bi,


The signal on the scope was the signal going to one of the 3 legs of the y connected alternator.  As you could see it worked pretty well as a motor.  But when I stopped the rotor to try and draw current from the slip rings as I had done earlier the output from the slip rings was pretty low.  So I concluded that was not a good signal for inducing power into the locked rotor from a virtual rotating magnetic field.


Take care,
Carroll

Thanks for quick reply. I don't think I'd expect induction into the concentric field coil of a Lundell rotor, even if you used a true sinusoidal 3-phase. Kind of a different animal.
Can you reference or link back to what you did previously?
bi