# Mechanics and Electrical parameters

Do you have information about the electrical parameters of the motor (inductance, resistance,etc) and mechanical parameters(rotor inertia, friction of the motor,etc)? for the motor 37D

Hello.

The inductance of our 37D Metal Gearmotors is about 2.3 mH.

You can estimate a motorâ€™s electrical resistance by dividing its rated voltage (12 V for the 37D motors) by the stall current (5.5 A for the 37D motors). So for the 37D motors, that gives you a value of about 2.2 Î©.

We have not characterized the rotor inertia for our motors yet, but you could approximate something for that by determining the moment of inertia for the output shaft. The shaft is made of stainless steel and its dimensions can be found in the dimension diagram (which can be found on any 37D motorâ€™s product page under the resources tab). By the way, I would expect the rotor inertia to become negligible once anything of substantial inertia is attached to your motor or once your motor is loaded in a real application.

You can determine a motorâ€™s viscous friction constant by dividing the no-load current by the no-load speed and then multiplying by the motor torque constant. The motor torque constant is the inverse of the inverse of the slope of the current-versus-torque line in the performance graphs.

-Patrick

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