YASKAWA GA800 Technical Reference page 747

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PID Feedback Loss Detection
The PID feedback loss detection function detects broken sensors and defective wiring between the drive and sensors.
Use the PID feedback loss detection function when you use PID control. If the feedback signal is too low, the motor
can suddenly accelerate to the maximum output frequency. This function prevents such risks to the load.
The drive uses two methods to detect feedback loss:
• PID Feedback Loss [FbL]
Set these parameters for the PID feedback loss detection function.
The drive detects feedback loss when the feedback value is less than the value in b5-13 for longer than the time in
b5-14.
– b5-12 [Feedback Loss Detection Select]
– b5-13 [PID Feedback Loss Detection Lvl]
– b5-14 [PID Feedback Loss Detection Time]
• Excessive PID Feedback [FbH]
Set these parameters to set how the drive detects a feedback level that is too high.
The drive detects too much PID feedback when the feedback value is more than the value in b5-36 for longer than
the time in b5-37.
– b5-12 [Feedback Loss Detection Select]
– b5-36 [PID High Feedback Detection Lvl]
– b5-37 [PID High Feedback Detection Time]
Figure 12.36 shows the operation principle when the feedback value is too low, and the drive detects feedback loss.
The operation is the same when the drive detects too much feedback.
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PID Sleep
PID sleep stops drive operation when the PID output or the frequency reference is less than b5-15 [PID Sleep
Function Start Level]. This function shuts off drive output after the motor decelerates to the set frequency.
The drive will automatically restart the motor when the PID output or the frequency reference is more than the b5-15
value for the time set in b5-16 [PID Sleep Delay Time].
Figure 12.37 shows the PID Sleep function.
YASKAWA SIEPC71061737D GA800 Drive Technical Reference
Figure 12.36 Time Chart for PID Feedback Loss Detection Time
Figure 12.37 PID Sleep Time Chart
12.3 b: Application
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