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#14
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Re: Failed attempt to explain JAG linearity
Quote:
120Hz Victor v_emf = 12 - i_free*R/duty......................varies with 1/duty 15kHz Jag v_emf = 12*duty - i_free*R .....................varies with duty The 2kHz Victor is very close to the Jag. I wrote a LABVIEW simulation (see attch hbridge.vi) of a one sided Hbridge and the curves (see attch thumbnail) verify what we are seeing. As Al says, this is independent of coast or brake mode however, with the JAG, the "off" ckt is essentially the brake mode since the diode is always conducting..the only difference is for the voltage drop across the diode. This is why I did not see any non spike Vemf in the JAG waveform ..only duty cycle variations. Feel free to run the program and vary the inductance to see its effects. I used a nominal 120uh which is close to what people have measured in the past. I think the max posted was 230uh. I wonder what all this is worth? Since I have not seen this mentioned in any of the Hbridge tutorials maybe I'll publish a paper. Lets see...what should I call it. How about "Special Theory of Nonlinearity: An Inconvient Truth of Low Hz Hbridges". Maybe the good folks in Stockholm are reading ChiefDelphi threads Well, it might be worth a minor entry to Wikipedia under Hbridge theory or under alternative ways to spend time when Friday night TV is on. Erick...put those beers on ice...assuming Al doesn't send me back to the showers again. RIP thread ; Last edited by vamfun : 16-05-2009 at 20:25. Reason: Added jpg for those that dont have LABVIEW |
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