Maximum input current

Hi,

Does someone know what is the maximum input current i can feed the ODrive with if it has two motors connected?

Thank you very much!

Er, the ODrive needs to be “fed” with a voltage between 10-50V. It will then draw as much current power as it needs, to move the two motors according to whatever commands you give it. The higher your supply voltage, the less current you need to deliver the same power.

Unless the motors are spinning at full speed and producing full torque at the same time (which is very rare in a servo application - you only see this in a traction application), ODrive will draw significantly less current than it supplies to the motors. For example, if the motors are stationary but sustaining 30A, the ODrive might draw between 1-3A from the supply, depending on the resistance of the motors.
To work out the “stall power”, simply multiply the square of the current in the motor by the resistance of the motor (i.e. P=I^2 R). Then to get an estimate of the supply current, divide that power by your supply voltage i.e. I=P/V
Of course, if the motor is spinning fast, the power draw will be higher because you are producing mechanical power. Multiply the torque in N.m by the speed in radians/sec to get the mechanical power in Watts, add that to the electrical power you just calculated, and multiply the total by 1.1 (because ODrive is about 90% efficient). Again, input current I=P/V

That said, I would be uncomfortable using the ODrive at more than about 50A DC-bus current, unless I had active cooling, because of the thickness of the copper tracks on the board. But most applications will not get anywhere near that.

What is your application?

Thanks for your fast reply, Towen.

I’m using the driver in order to control two eX8108 105 KV Brushless Motors (https://shop.iflight-rc.com/index.php?route=product/product&product_id=959).
I wanted to know what would be the maximum current that i could “feed” the Odrive in order to obtain the motor’s maximum torque.
Being that said, my doubt is: which is the maximum current i can feed the oDrive (from a power source) without damaging it and getting full torque?

That motor has a max current of 24A, well within ODrive’s capabilities. It has a resistance of 0.186 Ohms, so at stall (max torque, zero speed), it will take 107 Watts. That means from a 48V supply ODrive will draw about 2.3 amps, or from a 24V supply it will draw 4.5A. Double that for two motors.

The ODrive itself is a current regulator. It controls the current in the motor, so as long as you set the motor.config.max_current to 24, you will not damage the motor. (provided you can keep the motor cool)

There is no upper limit on the current rating of your power source, only the voltage. For example, you can connect ODrive directly to a battery, which has a very high maximum current in the thousands of amps, as long as its voltage is less than 56V, or less than 24V if you have the 24V version.
I would advise to use a fuse with any battery, though. If you have two 750W motors and a 48V battery, then a 30A fuse should be sufficient.

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Thank you very much Owen, your answer has been very helpful!

Jan Calduch :slight_smile: