# dc brushless motor specs for generator

Hello i have done my research and have found varying information relating to the speed at which you must drive a motor to get a desired output and that it is dependent upon back EMF however i am very interested in how much torque i require to rotate the motor.

I have a model aircraft engine and wish to use pulleys or gears to get a good speed and torque to drive multiple brushless motors but i need to work out my ratios for the pulleys or gears (have not yet decided, probably pulleys) can anyone give me any insight.

I am looking for equations to be applied to any brushless motor to calculate the generation voltage, amperage and the required torque based upon any specifications of a motor.

How do I calculate the voltage, current and torque for a BLDC motor? Can I find this information in a datasheet?

• If you did any research, you would know that before posting a question here, you should include hard numbers, model numbers, and actual goals... Not just a vague "I want to do something with something". – R Drast Mar 7 '17 at 10:54
• The torque required to drive the generator depends on the load attached to it – user28910 Mar 7 '17 at 14:38

## 1 Answer

As a rough guide, you can expect a motor used as a generator to produce the voltage it required as a motor at the speed at which it operated as a motor. At full load, the torque required is comparable to the torque it produced at full load as a motor. You must consider that a brushless DC motor produces AC as a generator. You must also consider losses in the motor that are comparable to losses operating as a generator.

That guide is applicable to any motor, but some types of motors require external circuitry for use as generators just as a brushless DC motor requires external circuitry for use as a motor, but will generate AC without external circuitry. Some types of motors require internal modifications for use as generators.

• I did not include models and figures because I gave an application and a generic question asking for a method or theory on how you could obtain figures from any brushless motor. To be more specific are there equations to help calculate a motors voltage and current with the required torque Charles Cowie thank you for your help. – Chris James Mar 8 '17 at 19:34