Ulvac UTM3400 Series, Instruction Manual

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SECTION 9 TROUBLESHOOTING
72
9
9.4
Power Failures
When a power interruption occurs, the motor inside the turbo molecular pump immediately
begins regenerative braking. The magnetic bearing will use this generated electricity to keep
functioning and the rotor inside the turbo molecular pump will continue being levitated. The
rotation will slow down due to the regenerative braking and eventually the rotor will be supported
by the touchdown bearing. Table 9-2 shows the number of revolutions and period of time that will
elapse before being supported by the touchdown bearing, when the power fails at the rated
speed.
Table 9-2
Time and Rotational Speed During a Power Interruption Before being Supported
by Touchdown Bearing
(Note 1) The time is typical for regenerative braking from the rated speed.
Actual time will vary depending on vacuum conditions inside the pump and the rotational
speed when the power fails.
Pump model
Rotational speed before support
by touchdown bearing Period of time before support
by touchdown bearing (Note 1)
UTM3400 Series 7500 rpm 9 minutes or less