10 Safety Functions - Edwards STP-L301 Series Instruction Manual

10 Safety Functions

10.1 Power Failure
<Operation at a Power Failure>
When the power voltage drops below 170 V (in case of 200 V specification) or below 85 V (in
case of 100 V specification) due to power failure, the normal operation of the magnetic
bearing is maintained using the regenerative energy of the rotating rotor (backup operation
during a power failure).
1) When the rotational speed is 25,000 rpm or more at a power failure:
I. 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 "POWER FAILURE". Also, an alarm signal is
output from I/O TB1 ALARM OUT terminals (10)-(9) and (10)-(11).
When the number of rotations goes down to 20,000 rpm, the backlight of the LCD
extinguishes and the alarm signal output is reset.
When the number of rotations goes down to approximately. 17,000 rpm, the rotor
lands on the touch down bearing and stops. The "FAILURE" LED extinguishes
and the LCD is turned off.
II. The STP control unit does not detect a power failure of less than 2 seconds,
continuing rotating the STP pump.
2) When the rotational speed is 17,000 rpm or more and less than 25,000 rpm at a power
failure:
The STP control unit detects a power failure of approximately 0.02 to 0.14 seconds and
the STP pump decelerates.
At this time, the "POWER" LED extinguishes and the "FAILURE" LED
illuminates. The LCD displays "POWER FAILURE". Also, an alarm signal is
output from I/O TB1 ALARM OUT terminals (10)-(9) and (10)-(11).
However, when the number of rotations is less than 20,000 rpm at the occurrence
of a power failure, no alarm signal is output.
When the number of rotations goes down to 20,000 rpm, the backlight of the LCD
extinguishes and the alarm signal output is reset.
When the number of rotations goes down to approximately 17,000 rpm, the rotor
lands on the touch down bearing and stops. The "FAILURE" LED extinguishes
and the LCD is turned off.
◇ A power failure is detected faster the less the rotational speed at the power failure.
3) When the rotational speed is less than approximately 17,000 rpm at a power failure:
The STP control unit does not detect the power failure; the rotor lands on the touch
down bearing and stops.
STP-L301/L451 Series Instruction Manual
10-1