5 SAFETY FUNCTIONS
The STP pump 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 in the STP Control Unit Instruction Manual (C), contact Service office.
5.1 Safety functions
5.1.1 Power failure
When the power voltage drops 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 "TECHNICAL DATA" in the STP Pump Instruction Manual (B).
1. When the rotational speed is at backup rotational speed or more at a power failure:
• The STP control unit 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" or "POWER FAILURE" (SCU-350). An alarm signal is output
from REMOTE X7 pins (14)-(33) and (15)-(33). (SCU-350 series: I/O TB1 ALARM OUT
terminals [9]-[10] and [11]-[10]). 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 STP control unit 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 STP control unit does not detect the power failure. The rotor lands on the touch down
bearing and stops. Refer to "TECHNICAL DATA" in the STP Pump Instruction Manual (B).
5.1.2 Operation after a power recovery
The magnetic bearing operation, LED and LCD messages are recovered after a power recovery.
The "FAILURE" LED extinguishes.
Press the "START" switch to reaccelerate the STP pump.
Note: Establish a procedure so that the power can be supplied to the STP control unit immediately
after a power recovery.
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