Archive: Jan 2014

The How and Why of the Centrifugal Clutch

As leaders in the design and manufacture of custom centrifugal clutches, we’re often in contact with people who want to know how they work, and what their advantages are. Simply put, their advantages are many—but here we aim to explain why and how.

The main purpose of the centrifugal clutch is to start loads efficiently and save energy. In essence, this type of clutch connects the prime mover (the motor, engine, turbine, etc.) to the load to be accelerated in a way that, in start-up mode, the prime mover starts without any load imposed on it. As the motor speed increases, it develops near-maximum torque before the clutch is radically activated to connect the load and accelerate it smoothly to rated speed—with no slippage and 100% efficiency.

When using the right centrifugal clutch, shock loading of the power train is eliminated, making for smooth acceleration and providing overload protection to both the motor and the machinery. Consider this: The demand of the average motor at start-up is significantly greater than when running at rated speed and load. Without a clutch, this high inrush current can last several seconds at least, but with a centrifugal clutch, this is only a fraction of a second, resulting in maximum torque with minimum current draw. The clutch does the slipping and dissipates the heat, and the added advantage is eliminating expensive starting apparatus.

So what should you consider when selecting a centrifugal clutch?

First you must take into account the effect of the load or mass to be accelerated; i.e., a high-inertia load will require a longer acceleration period, so the clutch must have sufficient mass to dissipate heat generated. When there is a frequent starting cycle, heat can be problematic and overheating can occur, but allowing the clutch to cool off can return it to its rated efficiency.

The centrifugal clutch should be selected so that the load is applied where maximum torque is developed by the motor; the clutch can be adjusted for capacity by varying weight of the operating mechanism in the clutch, which can increase the capacity of the clutch and achieve a wide range.

While no one particular clutch is suitable for all conditions, working with the right experts can help guide you to the right size/capacity for your application. In the end, the centrifugal clutch will save energy and start loads efficiently, eliminate the need for starting equipment, allow use of a smaller motor, and provide smooth acceleration.