How many additional caps 12s foc 6374

General topics and discussions about the VESC and its development.
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How many additional caps 12s foc 6374

Postby ieatflys » 01 May 2017, 19:00

Hello there.... im building a mountainboard using the torqueboards vesc (x4) and implementing a 6374 motor at 190kv on 12s.....

My powerwires are undoubtfully going to be long and i have read in many places that i will need to add capacitors across the leads near the vesc to help make up for the battery cable length.

My question is.... is there a rule of thumb to follow for how many capacitors to add per length of battery wire? My battery will be going through a pcb a switch or two and then battery wire then be vesc... should i be counting my diy pcb as battery wires? Im assuming so.

If i may ask while i am here as well. My 190kv motors on 12s will come close the the erpm limit... what is the actual limit? And is there a way to set the erpm limit so i do not exceed it?

Thank you all much!

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Re: How many additional caps 12s foc 6374

Postby benjamin » 02 May 2017, 08:15

I have been running a few simulations to figure out how many capacitors are needed, and I think you should be fine with the default ones. If you want to calculate it yourself to be sure you can have a look at my video:

Links to my SVM simulator and ltspice models are in the description.

A problem I can see with your setup is that the VESC4 in general has some problems with FOC for some motors with too low inductance, and the 190kv turnigy motors are just at the limit. If you are careful with all the parameters you should be fine, but if you make mistakes with the motor parameters for FOC you can kill the DRV. I recommend using a lab power supply with less than 20V when measuring the FOC parameters and getting the motors running for the first time, and then use the parameters when moving to the battery. Otherwise you can run on BLDC or wait for the VESC6 to become available (which should be soon, the beta batch is about to ship) which is much more reliable on FOC and can handle high ERPMs easily.

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