The Performance of Air motors. A complete breakdown

While many people understand the durability and versatility of air motors, there still seems to be some question around how well they really perform. What kind of power output do they provide? What about torque? Speed? Braking? Air consumption and efficiency? Understandably, consumers have more than just a few questions when it comes to an air motor’s performance.   

Because of its unique design, the output of the air motor can be modified to produce a wide range of torque. This is one of the many reasons the air motor is so versatile in its application.  

In this article, we’ll dive into every performance question surrounding the air motor. We will also delve into the precise source of the air motor’s performance, explaining why it operates with such efficiency.  

Air Motor Performance and torque 

The air motor’s performance is determined by the air pressure at the inlet. This is what is referred to as “inlet pressure.” If powered by a constant inlet pressure, the performance of the air motor is linear when defined by a torque/speed relationship. This allows the air motor to operate efficiently over the entire torque curve, from free speed (idling speed) to standstill without any harm to the motor.  

Starting torque of an air motor 

The starting torque is the torque generated by a motor when a blocked shaft is exposed to full air pressure. It’s worth noting that vane air motors generate varying levels of starting torque in this context.. Because of the differences in position and number of vanes in the motor, starting torque will vary widely from application to application.  

Every air motor includes a minimum starting torque value, which can be considered the guaranteed value during startup. The variation in starting torque predominantly relies on the air motor type and should be evaluated accordingly. The torque variation is greater for reversible motors when compared to non-reversible motors.  

Stall torque of an air motor  

The stall torque refers to the torque an air motor generates at the instant it halts after being braked to a stop. To put it differently, stall torque is the torque produced when the motor comes to a complete standstill. Although it’s not typically a variable detailed in tabulated data, calculating an air motor’s stall torque is a straightforward process.

A fair estimate of the stall torque of a motor can be found by multiplying the maximum power torque output by two. This means that for an air motor with a maximum power torque of 10 Nm, the stall torque would approximately equal 20 Nm.  

How does stall torque relate to braking? 

Stall torque has a direct relationship with the speed at which the brakes are applied to the motor. Slow braking speeds will produce lower stall torque; faster braking speeds will produce higher stall torque. The stall torque produced is largely dependent on the fact that the mass from the rotor increases the torque.  

Assessing the power of the air motor  

To put it as simply as possible, the power produced by an air motor can be calculated by multiplying torque and speed. The power output on air motors falls on a characteristic parabola curve or an upside down U shape. This means that maximum power output occurs at 50% of the free speed. In this sweet spot on the power curve, the torque produced is often referred to as “torque at the maximum output.”  

The working point for an air motor application  

Before an air motor can be effectively put to use in any new application, the working point must be found. The working point will vary will each application but can normally be found where the desired operating speed for the motor meets the torque required at that same point.  

The air consumption of an air motor  

As can be expected, the air consumption of an air motor increases as the motor speed increases. This means that the highest rate of air consumption is at free speed. However, even when the air motor is in a standstill condition, it still consumes air. In such a state, the rate of air consumed will be determined on the internal leakage of the specific motor, and will vary once again from application to application.  

How is air consumption measured?  

The air consumption of an air motor is measured according to the standard methods used for all pneumatic equipment. It is measured not with the actual volume that compressed air occupies in the motor, but instead as the volume it would occupy if allowed to expand to atmospheric pressure.  

Conclusion  

In comparison to electric motors, air motors have quite a few standout performance features. The most notable feature is that they can operate over the complete torque curve – from free speed to standstill. Their durable construction of the air motor allows for consistent performance throughout the torque curve without harming the motor.  

Furthermore, because the performance of an air motor is entirely depended on the inlet pressure, the output of power can be easily modified. Most machines achieve this by regulating the air supply with throttling techniques or some type of pressure regulation.  

There is no denying it’s versatile application and notable performance features. The air motor can be utilized in a wide range of industrial applications. If you’re looking for more information on our air motor’s performance features, feel free to reach out to us anytime.