The torque generated by the motor, and its speed of rotation, are dependent on each other.
This is a basic characteristic of the motor ; it is a linear relationship and is used to calculate the no-load speed and the start-up torque of the motor

The curve for the output power of the motor is deduced from the graph of torque versus speed. The torque vs. speed and output power curves depend on the supply voltage to the motor.
The supply voltage to the motor assumes continuous running of the motor at an ambient temperature of 20 C degree in nominal operational conditions.
It is possible to supply the motor with a different voltage (normally between -50% and + 100% of the recommended supply voltage).If a lower voltage is used compared to the recommended supply the motor will be less powerful.If a higher voltage is used, the motor will have a higher output power but will run hotter (intermittent operation is recommended).
For variations in supply voltage between approximately - 25% to + 50%,the new torque vs. speed graph will remain parallel to the previous one.Its start-up torque and no-load speed will vary by the same percentage (n%) as the variation in supply voltage. The maximum output power is multiplied by (1 +η%)2.
Example : For a 20% increase in supply voltage
Start-up torque increases by 20% ( x 1.2)
No-load speed increases by 20% ( x 1.2)
Output power increases by 44% ( x 1.44)