# How to select power source for robot actuator with known torque requirement

I am building a robotic actuator that will be backdrivable, this robot will have pretty low RPM. I will be using brushless DC motors. I am trying to figure out requirements for the power source. I have the motor data sheet, but we would like to run the motors at higher voltages to get more juice out of them. I know the required torque the motors would need to produce. Below is the derivation I used to find the required current and power. When I plug in all the known values, I get numbers that seem inaccurate. For instance, if I say req'd torque = 2.5 N-m, Kv = 473, max RPM = 50, I get current = 123 A and req'd power = 1.6 Watts.

I would really just like to know if I am going about this correctly as far as the calculation of the req'd values. I am also wondering if power required for stall torque would be equal to power required for no-load max RPM? *The 1.25 is a safety factor recommended on one of the links below. Also Ia = current of the armature. I assumed this was the same as req'd current but I am not sure.

Here are two links I used for my derivation:

https://en.wikipedia.org/wiki/Motor_constants

https://things-in-motion.blogspot.com/2018/12/how-to-select-right-power-source-for.html

This is the data sheet: • It is impossible to give an answer as there is no clear question. First hat you have to enter in your equations are units, then check if they match. You won't go far with simply inserting numbers without units. – Marko Buršič Sep 17 at 21:37
• To clarify my question: "I would really just like to know if I am going about this correctly as far as the calculation of the req'd values. In other words is the above derivation an accurate way to obtain required power for a brushless motor with known values of: Kv, RPM, and torque? I am also wondering if power required for stall torque would be equal to power required for no-load max RPM?" – Ryan C Sep 18 at 1:55