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What is a common motor efficiency? I'm at 72%

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ever.summer
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What is a common motor efficiency? I'm at 72%

So the motor company sends a video showing the motors they sent can do 5680 rpm at 28.8V, but a Flipsky 6.6+ VESC is only getting 4090 rpm at 29V in FOC mode...

I believe one of two scenarios are at play here:

1) the motor company has faulty measurement equipment and the motor isn't doing 5680 rpm

2) my VESC is only 72% efficient

Lets assume #1 is not the case, then is 71% efficiency common? Is there anything I can do beyond the awesome super easy motor setup that Benjamin made with his new VESC setup mobile app?

(BTW the video that the motor company sent has a clearly higher frequency sound, so I am assuming they are getting a higher RPM)

thewho
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Efficiency doesn't effect unloaded rpm. Did they maybe send you a motor with different kv? 

ever.summer
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That was my first thought - but the motor company sent a video of the same motor doing much higher RPM. I also thought, maybe their testing equipment is faulty but I can hear a higher frequency spinning sound in their video so I am assuming it is a higher RPM.

Is there something else that could be capping my highest RPM?

thewho
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Do you maybe have your erpm setting too low? (motor settings > general > rpm)

ever.summer
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ok so I got new motors from the company and the KV and speed tested perfectly. They won't admit it, but they definitely wound those first two incorrectly! Given my system, their first sample was 150KV and the correct sample is 200 KV (actually tested to 210KV but hey I'm not complaining)

Roger Wolff
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Building a motor with a LOW Kv is hard, making it higher is easy. Of course if you WANT to reach 15000 RPM and your motor has a KV of 10, then that's not ideal. 

 

As said before, the KV is completely separate from "efficiency". The KV determines the maximum RPM you'll  get at a certain voltage. It also determines the torque you'll  get from one amp of current. Lower KV -> higher torque.