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BLDC Motor Power limitation

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tecnico.solarboat
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Joined: 2018-06-28 14:43
Posts: 19
BLDC Motor Power limitation

Hello,

I´m using a VESC 75/300 to try to control a 3kW BLDC motor from CPMotion. The issue is that I can´t pull more than 2.6kW (peak) and I don´t understand why.

Motor specifications:

  • 48V
  • Voltage range 36V– 56V
  • 62.5A
  • nominal power 3kW
  • Peak power 5kW
  • Holding torque 6.66Nm
  • Peak torque14Nm
  • rated RPM 4300

Battery specifications:

  • 16.8Ah LiPo cells
  • 2-cell blocks in parallel and final configuration of 12 blocks in series
  • Maximum continuous discharge current 10C
  • Nominal voltage 44.4V
  • Minimum voltage 36V
  • Maximum voltage 50.4V
  • Power 1.5kWh

Motor datasheet: https://drive.google.com/file/d/1D8k6FQcWqnnuryVvoHNn4jWFncbsx65B/view?usp=sharing

Cheers,

Gonçalo 

TechAUmNu
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Last seen: 6 days 9 hours ago
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Joined: 2017-09-22 01:27
Posts: 574

What are your current settings at in VESC Tool? If you used the auto motor setup wizard then it will have picked an appropriate current limit for your motor.

A picture / screenshot of the real time current graph always helps us understand what is happening.

tecnico.solarboat
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Last seen: 10 months 2 weeks ago
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Joined: 2018-06-28 14:43
Posts: 19

Hi,

 

Sorry for the lack of context on the first post. We are actually building a racing solar boat and we are using the VESC 75/300 for our motor.

The problem we faced was during our races this summer, and unfortunately we don't have a test bench setup to test the motors and get the live data on the vesc tool.

But we are now working on that.

 

We can send the VESC configuration file, but after doing the auto-setup wizard it picked up a current limit of 135A.

 

Meanwhile we can tell all the info we got while racing this summer:

We actually managed to get peaks of 4kW but for very short periods (1s), the 2.6kW were actually the continuous max.

Also the maximum RPM was always around 3600rpm, but without load we get up to 4500rpm (which is also not the maximum of the motor).

The VESC was far from its max temperature limit and so was the motor.

Unfortunately, we didn't have access to the duty cycle and we don't know if it was maxed out.

 

We thought that with this information someone could have an idea of what the problem could be. Maybe the battery voltage is too low?

 

This month we are actually going to test the boat again and save as all the data of the controller and the motor.

We will also try 2 different propellers to change the load profile and compare the data with each propeller.

 

Thanks in advance,

Gonçalo Costa - Técnico Solar Boat

benjamin
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Joined: 2016-12-26 15:20
Posts: 487

It would be useful if you can do some logging with the VESC Tool app and post the log:

I have improved it quite a bit since the video, and you don't need to use an external app such as GPS Keeper any more.

tecnico.solarboat
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Last seen: 10 months 2 weeks ago
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Joined: 2018-06-28 14:43
Posts: 19

Thank you for helping us. When we test the motors and the boat again, we will log that info.

I hope it will be useful.

 

Best regards,

Gonçalo Costa