Once you know what speed and torque is needed for your application,the next step is to calculate the power required. When you know the required power, you can select an air motor which has the necessary power range.
Power is equal to the torque (in Nm) multiplied by the speed (in rotations per minute) divided by the constant 9.55 to obtain the power (in watts). To power up the motor therefore, you need both speed and torque working together, because if there is no torque, or no speed, then you won’t get any power.
Essentially, once the power starts, the torque increases, proportionally decreasing the speed until the power reaches a maximum level. Optimum power is reached at a torque for which the speed is at half the free speed (that is, half maximum speed), after which point the power starts to decrease because it is losing more in speed than it is gaining in torque. Therefore, you will always have an optimum working point where your motor is operating at maximum power where your motor is operating at maximum power.
To identify the right power range motor for the job, simply plot the working point on the torque/speed curve as shown in the diagram. If this point is below the torque/speed curve, the motor has the capacity to do the job. If the point is above the curve, however, the motor will not be able to do what you ask of it.
So, you have chosen a motor with a power range capable of doing the job required. To get the motor to work at the precise working point, as plotted on your graph, you can adjust the air flow or air pressure. If the speed is less critical for your operation, adjust the air flow to reduce the speed. If the torque is less critical, adjust the air pressure.
It is important to carry out these initial steps to calculate the power required and your optimum working point as this information will help to ensure you select the right power range motor for the job.
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