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Old 11-09-2015, 10:52 AM   #2313 (permalink)
MPaulHolmes
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Location: Maricopa, AZ (sort of. Actually outside of town)
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Michael's Electric Beetle - '71 Volkswagen Superbeetle 500000
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Quote:
Originally Posted by thingstodo View Post
I see pack amps, indirect. Is that accurate enough for doing an efficiency calculation? Or should I have a shunt and rig up a display of some sort?
It was accurate when I used a 100mV = 100amp shunt connected to the DC bus, so I wouldn't bother with doing that.

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Vd and Vq - do we need to do a vector sum or is it just the real power that is being measured? I think just the current doing work is measured ... it's been a while so I need to look up some stuff!
Ya, I get used to using the terms, and I forget what the heck they are. haaha. My understanding is, Vd is the voltage responsible for the stator field generation, so I think Vd*Id would be the instantaneous reactive power, and Vq*Iq + Vd*Id would be the true (or apparent) power being used by the system, so I guess the power factor would be Vq*Iq/(Vq*Iq + Vd*Id). Hey, I bet power factor would be a nice variable to see too.


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Can you do electrical RPM and mechanical rpm? That would show slip under various loads (and the slip DOES change). When you reach peak torque, the slip reaches a critical point, then the motor loses synchronization and stalls (don't ask me how I know). This would be good for the racers to determine how far they can push the motor, and what their absolute maximum torque out is!
This is one of the many reasons why you are straight out of Fort Awesome. You bet we can do electrical and mechanical RPM. I just didn't know it would be so useful!

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DC Volts and amps on the DC motor side would help - V and I in, V and I out. I'm struggling with the Cougar to determine how many MOSFETs failed and which ones.
Unfortunately I don't have DC voltage as a possible measurement We can look at the 3 phases of V and the 3 phases of I on the output side. We could then do an instantaneous Vphase1*Iphase1 + Vphase2*Iphase2 + Vphase3*Iphase3 to get the instantaneous power out?

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The next video should be better (not as much background noise). I think I figured out (with the help of many tutorial videos) how to use Google Hangouts live to have 2 cameras and use a noise cancelling bluetooth headset so I can talk above the howl of the motors. So far, the main camera will be like the present videos. The second camera will be pointed at meters and displays. It should be synchronized so I don't need to spend time merging things together after taking the video. All I should need to do is remove the extra-boring stuff, or the parts when I have to look for tools, chase the cat away, etc
That is awesome. I would very much like to know how to do it too when you figure it out.

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I may run out of multi-meters So - Paul - which information is most useful to you?
Gosh, I think there are a bunch of interesting tests I would like to see. First I think it would be good to see that Id really is following IdReference, and Iq is following IqReference on your motor. Then, because we used the "autotune" PI feature, I would feel good about it. I'm not sure of what the new RTD format is, but this data can be streamed right to a text file, and then pasted into Excel. That would allow updates at maybe 1KHz rather than just 10Hz, not that 1KHz would be required. You wouldn't see it live as it happens, but could go back and see what the last minute looked like on a graph.
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