Search found 161 matches

by donob08
Jul 24 2010 2:02pm
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 display...
by donob08
Jul 21 2010 8:21am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 = Iphase limi...
by donob08
Jul 20 2010 9:09pm
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 is of equal i...
by donob08
Jul 19 2010 9:25pm
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 cut Iphase ...
by donob08
Jul 19 2010 4:50pm
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 223....
by donob08
Jul 15 2010 8:57am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 is getting...
by donob08
Jul 15 2010 7:39am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Let's do an experiment

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 throttle)...
by donob08
Jul 15 2010 6:31am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 think we need...
by donob08
Jul 14 2010 4:39pm
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 think the...
by donob08
Jul 14 2010 1:03pm
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 "Current mult...
by donob08
Jul 14 2010 12:35pm
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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. Everything e...
by donob08
Jul 14 2010 9:47am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 Current Batt ou...
by donob08
Jul 14 2010 8:03am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 result, PW...
by donob08
Jul 13 2010 6:53pm
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 understanding...
by donob08
Jul 13 2010 4:37pm
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 sweat. My interes...
by donob08
Jul 13 2010 3:11pm
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 current sensing. I...
by donob08
Jul 13 2010 10:49am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

A shorteer hopefully clearer presentation

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 =F(throttle)Vbatt + Vbemf ââ...
by donob08
Jul 13 2010 9:39am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 loop for all pos...
by donob08
Jul 13 2010 8:39am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 it doesn't ...
by donob08
Jul 12 2010 3:46am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Some news worth sharing

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) is just a ...
by donob08
Jul 11 2010 1:42pm
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

Eric I think it may be contagious.. I think below you wrote Iphase approximately equals Ibatt/D. ;-) Don Using motor speed to regulate duty cycle would require knowledge of the motors Kv constant (which will be different for different motors). It's generally easier to estimate phase current using Ib...
by donob08
Jul 11 2010 11:37am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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. The best w...
by donob08
Jul 11 2010 11:17am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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
by donob08
Jul 11 2010 10:59am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 "cause effec...
by donob08
Jul 11 2010 10:37am
Forum: E-Bike Technical
Topic: **Important** reality check on motor, voltage, current etc.
Replies: 360
Views: 30972

Re: **Important** reality check on motor, voltage, current e

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 smaller than tha...