Electromagnetic clutches are used in a wide variety of applications. Ogura General Purpose clutches are typically mounted on engine shafts and used on outdoor power equipment. When designers look to specify an electromagnetic clutch on a new application, they should consult with Ogura based on our application experience. We can review the application details in order to guide you to the best result.

One of the first questions we will ask is, "What is the clutch turning?" The reason is that inertia of the rotating device is very important. Very high reflected inertia to the clutch means very high engagement energy. We will also ask about RPM at the clutch because engagement energy is proportional to the inertia multiplied by speed squared.

When a large mass is being turned, the engagement energy at the clutch is relatively high. If the energy is above the acceptable limit, there is possibility that the clutch can slip. All clutches slip momentarily upon engagement, but any prolonged slipping will generate excess heat that the clutch cannot dissipate. Localized slipping and heat can cause galling of the clutch friction surfaces. This can lead to premature failure. One way to reduce the engagement energy of a large inertia application, is to lower the speed. If engagement occurs at 800 RPM instead of 2400 RPM, the engagement energy is reduced by 88.9%. Some equipment manufacturers can advise or put controlled limits on the speed at which the electromagnetic clutch can engage, in order to improve reliability and longevity of the equipment.

The engagement of an electromagnetic clutch is quite quick. This means that all energy needs to be absorbed by the friction surfaces in a very short amount of time. One way to spread the energy over a longer time period is to use a soft start controller on the equipment. Although the engagement time is quick, let's say 1.0 to 1.2 seconds, it is still 4 or 5 times slower than natural engagement times. The clutch still wears around the same rate, but the shock load to the system is generally improved.

Gas or diesel engines produce torque spikes, so it is not possible to just specify clutch torque based on the average torque that the engine provides. In other words, the clutch needs to handle worst case or highest torque spikes. It is not uncommon to specify a clutch that is rated for 3x the nominal torque of an engine.

When making the selection of an electromagnetic clutch for a new application with high inertia load , it is possible to simply make sure that the clutch is more "powerful" than the engine. In other words, if the clutch can handle the highest torque spike of the engine, it will prevent destructive slipping and simply stall the engine. It is then better to stall the engine as opposed to slipping a cultch and potentially causing unwanted downtime and repairs.

Ogura's GT and MA series of General Purpose clutches range in torque from around 110 lb-ft to 400 lb-ft for engines ranging from 5 HP to 40 HP. Bore sizes for most models correlate to popular engine shaft sizes of 1" to 1.7/16" but custom designs can be made for the right quantity. Most mobile application clutches have 12V coils but other voltages such as 24V can be available for certain sizes and quantities. Soft start controllers are available for these clutches.

Benefits of using an Ogura General Purpose clutch:

• Long life
• Safety
• Built for outdoor operation
• Fuel and energy savings
• Remote starting option
• Many years of proven success
• For use with operator presence controls
• Available with a soft start controller
• Custom designs available based on minimum order quantities
• Reduced engine load on cold weather starts
• Increased operational life of driven equipment
• Simple installation

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