Figure 9: Speed-Torque line at different input voltage

By plotting the maximum continuous torque requirement over the speed-torque lines for various voltages, it can be visually understood that to maintain constant torque, the voltage must increase as speed increases. Maintaining constant torque is also equivalent to maintaining constant acceleration, and having constant acceleration can be very desirable in many motor control algorithms.

Figure 10 below also shows that if a constant torque of 20 mNm is required, there is a “dead-zone” from 0 to 7.2 V where the motor will not move and will be at a stall torque condition. The motor should not be run in this range because running it at its stall operating condition for any length of time can damage the motor. This dead-zone information should also be shared with your teammates working on the motor controller, and they should be sure to go from directly from zero input to the edge of your dead-zone (7.2 V) when they turn it “on.”⁹ Typically, it is desirable to keep this dead-zone small, not only because it broadens your voltage operating range but also because large input jumps to a motor can wear the motor faster. This is particularly important if you plan on switching motor directions frequently.