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Methods of modifying the motor performance

Throttling and pressure regulation are two methods to modify the performance of an air motor - throttling and/or pressure regulation. The conditions for the application decide which method is preferable.


Throttling air motor

A throttle is usually fitted into the motor’s inlet, although it can also be fitted into the exhaust.

The benefit of throttling the inlet is that air consumption is reduced, whereas throttling the exhaust air maintains a slightly higher starting torque.

When it is desirable to maintain a high starting torque but reduce running speed – throttling is the best method of modifying the motor’s output.

Pressure regulation

Pressure regulation air motor

When using a pressure regulator it is always fitted into the inlet of the motor. The use of pressure regulation is ideal when control of the stall torque is required and a high starting torque unimportant.

Motor performance with other air pressure

All performance graphs of Atlas Copco air motors are given for an inlet pressure of 6.3 bars. For other air pressures the performance curves must be recalculated.

To calculate performance data the motor data at 6.3 bar has to be multiplied by the correction factor shown in table below.

Another way to find out how to pressure regulate or throttle motors is to use the Air Motors Selection Program.

Correction Factors
Air Pressure   Output Speed Torque Air Consumption
BAR PSI        
7 101 1.13 1.01 1.09 1.11
6 87 0.94 0.99 0.95 0.96
5 73 0.71 0.93 0.79 0.77
4 58 0.51 0.85 0.63 0.61
3 44 0.33 0.73 0.48 0.44