# Motor power, Amperage and Voltage

Hey all!

I was wondering, what is the relationship between the voltage and amperage supplied to a motor and the motor’s speed? Is the speed dependent upon power, which is the product of the two?

Thanks a lot de geso!

no load at a certian voltage = high rpm and low amperage (the rpm of different types of motors vary of course)
high load at certian voltage = low rpm and high amperage

voltage multiplied by amperage = power

so to get a motor to run at higher rpm add more voltage or current to the motor

however how much voltage and current you can inject into a motor is limited by the specifications of the motor, motor controller, and of course the battery itself

for example if a motor runs at 100 rpm at 5V and draws 0.1A
but under the loads you will be placing on the motor it pulls 3A at 5V
you need to have a motor controller that can continuosly draw a little more than 3A of current, so say a 5A rated motor controller, in the case that the motor stalls and pulls say 4.5A

to run the motor at higher rpms you would have to get a higher voltage battery and a higher rated motor controller since the load on the motor will go up and draws more current which your electronics have to be able to take. All motors are also rated for maximum voltages and amperages, its important not to exceed those or you can easily risk burning out or overheating the motors.

You were also asking about the CIM motor on the official forum. All data is on the product page.
http://www.vexrobotics.com/217-2000.html

Stall current (which is what you care about most) is 133A. Free speed current is 2.7A. With a typical load it will need about 27A.

Hi Ika Musume,

AURA’s educational video from last year covers the basics of Motor Torque, Speed, and Current - the video is based around the 393 motor but the principles should be the same for the CIM motor.

Jack