Edwards SCU-350 Series

SCU-350 Series Control Unit for Turbomolecular Pump
MT-21E-201-E
Page 75
6
MAINTENANCE
6 MAINTENANCE
The SCU-350 is provided with safety functions for various abnormalities/errors. If an abnormality/error
is found when using the STP pump, check it and take measures in accordance with the following
procedures. If you cannot trace it or if the STP pump does not function normally after the
troubleshooting, fill in the necessary information in the "Return Declaration" and fax it to Service office.
6.1 Safety functions
6.1.1 Power failure
When the power voltage drops below 80 V due to a power failure or another fault, the normal
operation of the magnetic bearing is maintained at the high rotational speed using the regenerative
energy of the rotating rotor (backup operation during a power failure).
The lowest rotational speed to which the magnetic bearing can operate at a power failure is called a
backup rotational speed. The lowest backup rotational speeds is approximately 15,000 rpm
1. When the rotational speed is at backup rotational speed or more at a power failure:
The SCU-350 detects any power failure of 2 seconds or more and the STP pump decelerates.
At this time, the "POWER" LED extinguishes and the "FAILURE" LED illuminates.
The LCD displays "POWER FAILURE". An alarm signal is output from I/O TB1 ALARM OUT
terminals (10)-(9) and (10)-(11). When the rotational speed reaches 20,000 rpm, the rotor lands
on the touch down bearing and stops. The "FAILURE" LED extinguishes and the LCD is turned
off.
The SCU-350 does not detect a power failure of less than 2 seconds and the STP pump will
continue to rotate.
2. When the rotational speed is less than backup rotational speed at a power failure:
The SCU-350 does not detect the power failure. The rotor lands on the touch down bearing and
stops.