8 MAINTENANCE
The SCU-801 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.
8.1 Safety functions
8.1.1 Power failure
When the power voltage drops below 160 V in 200 V specification or drops below 80 V in 100 V
specification 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 vary according to the model of STP
pump used, refer to Table 29.
1. When the rotational speed is at backup rotational speed or more at a power failure:
The SCU-801 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 "Mains Failure". An alarm signal is output from REMOTE X7 pins (14)-(33) and
(15)-(33). When the rotational speed reaches the backup rotational speed, the rotor lands on the
touch down bearing and stops. The "FAILURE" LED extinguishes and the LCD is turned off. The
alarm signal output is reset.
The SCU-801 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-801 does not detect the power failure. The rotor lands on the touch down bearing and
stops.
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