![]() Outrunner-type motors are designed differently than the small electric motors you see in most devices. Playing around with the above equations, Power input, power output, RPM for a given prop, or device speed for given current, and many other calculations can be made. Once the propeller is choosen, motor working parameters can be back-calculated.Įquations above, also allow for finding the best approach to a motor, from known Rt and propeller. Of course, the “perfect” propeller is almost impossible to be found, but a very good approach can be achieved. Please note that required torque must include any torque in the arrangement. Regarding to battery life, max efficiency is a better option.įrom Propeller series curves and/or software ….Ĭhoose propeller (with limited diameter, play with Area and Pitch):Ģ-] Propeller required torque at RPMmax. But for such a ROV, its not needed.Īre we going to work at Max power output, or at max motor efficiency ? Required propeller thrust power: Pp= Rt x Vmax (Watts)ĭevice acceleration could also be imposed by thrust and Rt comparison. Torque: Motor is able to turn the prop at required RPM. Intallation requirements, physical constraints (maximum allowed prop diameter, …. ![]() Total device drag is known: Rt (Total resistance). MOTOR MAXIMUM EFFICIENCY: (Better mechanical output to electrical work ratio)Ī device is wanted to be moved through water by means of a propeller arrangement. Η= (V- I Rm)(I - Io)/(V I): V and I= working voltage and current. Η= Mechanical power out/electrical work in ![]() Kq= 30/(pi Kv): Kq= Torque constant.(units = N m) ![]()
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