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  1. D

    **Important** reality check on motor, voltage, current etc.

    I have one last idea I keep forgetting to offer. If the Cycle Analyst had an input for throttle voltage, throttle position would be a good indicator of the value of D in the PWM control. Since the Cycle Analyst knows Ibatt it could determine a good approximation of Iphase. If the Iphase were...
  2. D

    **Important** reality check on motor, voltage, current etc.

    I should say PWM can be used to limit Iphase. When it is used in that way it can no longer control speed. It can control one or the other NOT both. If we want to make D such that DVbatt-Vbemf = const Iphase limit for Iphase greater than I phase limit. (DVbatt –KVConst * Speed)/R =...
  3. D

    **Important** reality check on motor, voltage, current etc.

    Eric I'm thinking this should be my last note in this thread. I don't want to bicker with you. The reason we use PWM is to control speed. That is a well understood concept. If it also could control Iphase, that would be a nice freebe. Unfortunately it cant by itself. The value of Vbemf...
  4. D

    **Important** reality check on motor, voltage, current etc.

    Eric I think Luke's point was that while the technique presently used limits Ibatt, it has no control over Iphase. I phase is mainly determined by Vbemf. Ibatt limiting really doesn't solve the high motor current problem. As Luke has been saying it is Iphase that matters. The only way to...
  5. D

    **Important** reality check on motor, voltage, current etc.

    I think I’m on the right page now and I figured a measure of what I phase will be as a function of Ibatt limit, the limited battery current. If I’m correct then when Vbatt = 100 volts and Rp = 0.1 ohms and we set Ibatt limit to 50 amps, the phase current at low or no speed will be...
  6. D

    **Important** reality check on motor, voltage, current etc.

    Luke, Tiberius I agree the Current Limit situation is different. And more importantly, I need to work on remembering that we are talking a specific instance here. There, I think Tiberius' words that Iphase = Power In /Vemf at that time make things clear. I don't think it is because Vphase...
  7. D

    **Important** reality check on motor, voltage, current etc.

    I know I don't explain things in a way that many of you find understandable. Let's look at data. Set your bike up with the wheel off the ground Using CA or whatever measure/record the battery current at full throttle Repeat the process but with 1/2 throttle. Look at the ratio of Ibatt(half...
  8. D

    **Important** reality check on motor, voltage, current etc.

    Your quote says just what we need to correct. It says phase current increases. It does NOT. Phase current is divided down. But because battery current is divided down more, phase current becomes a multiple of battery current. This misunderstanding or misstatement by Luke is just what I...
  9. D

    **Important** reality check on motor, voltage, current etc.

    Guys I'm totally happy saying current multiplication happens in PWM. I would just like everyone to be clear that is a multiple of a much REDUCED current so that the Iphase is equal to Ibatt original *D where D is a fraction less than one. I was concerned that the multiplication made people...
  10. D

    **Important** reality check on motor, voltage, current etc.

    Eric I agree. Phase current is important. I'm just concerned that all this talk about "current multiplication" can cause people to miss the point that Iphase goes done when PWM is used. If the issue is totally aboout measuring Ibatt to infer an Iphase then, FOR SURE we need to consider...
  11. D

    **Important** reality check on motor, voltage, current etc.

    Eric My point is the question"Should the ratio of Iphase to I batt be what we are talking about"? We might as well talk about the ratio of Vphase to Vbatt. Then we would call it Voltage division. The "current multiplication' only matters to the wires connecting things to the controller...
  12. D

    **Important** reality check on motor, voltage, current etc.

    Maybe "Power Division" would be a good term. Before PWM Power Batt out = Batt Voltage * Batt Current Original Power motor = same After PWM simple case D =1/2 In this case we'll look at Power motor since it is determining things. Power Motor = Batt Voltage/2 * Batt Current Original /2...
  13. D

    **Important** reality check on motor, voltage, current etc.

    Luke I don't have a one word description. But what people should understand is that when you start PWM the phase current becomes a fraction of it's former value and since the battery current is intermittent it is divided by the same factor again. So if you look at the causal path, not the...
  14. D

    **Important** reality check on motor, voltage, current etc.

    Eric I'm an EE too. I don't think I've developed a lot of new understandings of concepts. But I do have an enlarged appreciation for the value a Glossary could have in situations like this. I think terminology was right up there with the biggest problems in this discussion. I guess new...
  15. D

    **Important** reality check on motor, voltage, current etc.

    Eric I guess the BIG Question is when will someone make a control with feedback so that Current is a function of Throttle. I would think the big gun motor guys would happily pay. I have no horse in this race. My little system gets me around on my errands with an acceptable level of...
  16. D

    **Important** reality check on motor, voltage, current etc.

    Eric I totally agree. Any feed back system making Iphase a function of F(throttle) is all we need. I have read so much about "Current Limiting" I assumed you were still riding that horse. I had to look back to see that on Page 18, July 12 you suggested a classic PI system based on...
  17. D

    **Important** reality check on motor, voltage, current etc.

    In think I could make my thought clearer. Without worrying how we got there: If D = F(throttle) + Vbemf/Vbatt Then Iphase and Torque are proportional to F(throttle)*Vbatt Simply: DV = D*Vbatt = F(throttle)Vbatt + Vbemf Driving Voltage = DV – Vbemf Driving Voltage...
  18. D

    **Important** reality check on motor, voltage, current etc.

    Eric If the feed back loop is effecting current, limiting, the throttle is NOT controlling Iphase. With a feedback loop throttle and speed determine Iphase. With my approach Throttle defines current. As an example for low speed, I phase will equal Iphase(safe) as set in the feedback...
  19. D

    **Important** reality check on motor, voltage, current etc.

    Eric I appreciate your comments. There are a couple of points I should clarify. The concept of F(speed zero) was only put in, as a place holder, because I sensed that D needed to be a nonlinear function of speed in order to control current. In fact, F(speed zero) will always be 1. Notice...
  20. D

    **Important** reality check on motor, voltage, current etc.

    I think this is worth reading if you get a chance. Lets make D = F(throttle) * F(speed) F(throttle) just equals 0 - 1 like always F(speed) = F(speed zero) + (actual speed*KV )/F(throttle)*(Vbatt aim speed*KV ). F(speed) = F(speed zero) + 1/F(throttle)*actual speed /aim speed F(speed zero)...
  21. D

    **Important** reality check on motor, voltage, current etc.

    Eric I think it may be contagious.. I think below you wrote Iphase approximately equals Ibatt/D. ;-) Don
  22. D

    **Important** reality check on motor, voltage, current etc.

    zapat Now, does using motor speed, as measured by the Halls, to help set the PWM duty cycle make sense? Making D a function of present speed relative to aim speed (Vbemf/Vbatt) as a multiplier on throttle position would set D to a safe level without measuring or trying to estimate Iphase...
  23. D

    **Important** reality check on motor, voltage, current etc.

    Zapat I'm not going to use the words > or <. I think you'll agree with my statements as the appear if you refresh the page. Don
  24. D

    **Important** reality check on motor, voltage, current etc.

    Zapat In case you are reading real time I needed to correct my explanation of my earlier correction. I edited just after posting to make greater into less in the first sentence. The edit doesn't show. Just the correct statement shows. I guess it is dyslexia. I'm bothered by the backward...
  25. D

    **Important** reality check on motor, voltage, current etc.

    Guys I think you missed that I corrected that statement to say Ibatt less than Iphase. I did that right after I read my post. I think what bothers me is that Iphase defines Ibatt, not the other way around. The low value of Vmotor = D*Vbatt says Iphase will be small and Ibatt will be...
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