Overrunning Clutch Selection Guide
OVERRUNNING: DUAL DRIVE AND TWO SPEED DRIVE
High-Speed Overruning and Low-Speed Engagement: (Overruning speed = 700 RPM and up) (Engaging speed = up to 200 RPM)
Smoke ventilation and gas mixing fans operate in high temperature environments. In order to prevent excessive thermal transfer from distorting the fan shaft, an auxiliary drive system is used to keep the fans rotating slowly when the main motor shuts down. Using a Cam Clutch at the auxiliary motor eliminates the need for manual clutch operation. Thermal expansion in the fan shaft must be absorbed through an expandable coupling. During main motor operation, the Cam Clutch rotates as a normal bearing, so service life is greatly extended. Please reference Figure 26 .
Fan Drive Systems
Fan
Bearing
Auxiliary Motor
Cam Clutch
Coupling
Figure 26: High-Speed/Low Engagement Energy Saving Application
This example shows a Cam Clutch installed in the auxiliary drive system of a steam turbine. The auxiliary drive system powers the turbine at low speed through the engaged Cam Clutch until steam pressure accelerates the turbine, releasing the Cam Clutch. Then the cam automatically disengages and runs as a high-speed ball bearing, because there is no mechanical contact in the clutch. Please reference Figure 27 .
Turbine Auxiliary Drive Systems
Cam Clutch Turbine
Coupling
Coupling
Auxiliary Motor (geared type)
Dynamo
Typical Series
Advantage
Can withstand extended continuous running
Cam Clutch Box
Minimal lubrication maintenance required
Figure 27: High-Speed/Low Engagement Energy Saving Application
The cam is the inner race overrunning type that lifts off Grease is sealed in, so lubrication maintenance is not required
BR-HT, BREU
MZ, MZEU
26
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