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5.1.13 System Safety
Every composite flywheel is inspected, spin balanced and tested to 110% over-speed in accordance
with NEMA guidelines. A patented dual-wall safety system ensures that in the unlikely event a fly-
wheel were to separate during operation, the inner housing would retain the carbon fiber. As the car-
bon fiber separates, it will expand and transfer its torque to the inner housing. The inner housing is
then allowed to rotate inside the outer housing. The cooling fluid in the outer housing, which sur-
rounds the inner housing acts as a dynamic brake. The stored energy is released in a controlled man-
ner as the flywheel / inner housing comes to a rest. The outer housing holds the entire safety system
and acts as a reservoir for the cooling fluid
The Liebert FS has been previously tested under the following fault conditions with no adverse safety
effects:
• Motor-generator AC short circuit
• DC short circuit
• Power Conversion Module failure
• Magnetic Levitation System failure
• Composite rotor failure
• Motor Rotor Failure
• Loss of Vacuum
Figure 43 Cutaway flywheel module
5.1.14 Cabinet
The Liebert FS is a compact design housed in a free-standing cabinet with a NEMA 1 construction
rating or IEC equivalent. No space is required between the back or sides of the cabinet and any walls.
The front clearance of 36" per the National Electrical Code is required. The Liebert FS accommodates
top (standard) and side entry cables. The Liebert FS can be rolled into place and go through standard
doors.
Outer Housing
Rotating Group
Inner Housing
Coolant