YASKAWA Varispeed E7 Instruction Manual And Parameter Description page 227

PI Feedback Loss Detection
When performing PI control, be sure to use the PI feedback loss detection function. Otherwise if the PI feed-
back gets lost, the Inverter output frequency may accelerate to the maximum output frequency.
When b5-12 is set to 1 and the PI feedback value falls below the PI feedback loss detection level (b5-13) for a
time longer than the PI feedback loss detection time (b5-14), a Fbl alarm (Feedback loss) will be displayed at
the operator and inverter operation is continued.
When the same happens and b5-12 is set to 2 a Fbl fault will be displayed on the digital operator and the
inverter operation will be stopped. The motor coasts to stop and the fault contact is operated.
The time chart for PI feedback loss detection is shown below.
PI Sleep Function
The PI sleep function can be used in two different modes which depends on the setting of b5-21.
If b5-21 is set to 0, the frequency reference/PI target value is taken as an input value for the sleep function. If
b2-21 is set to 1, the output frequency before the softstarter (SFS input, C1-
function input value.
If this value falls below the sleep level b5-15 for a longer time than the sleep operation delay time b5-16, the
inverter output will be stopped. If the value comes back to a value higher than b5-15 for a time longer than
b5-16, the inverter will resume operation.
Internal run command
External run command
The functionality of the Sleep function is also available with deactivated PI controller.
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PI feedback value
Loss detection
level
(b5-13)
Loss detection time
(b5-14)
Fig 6.50 PI Feedback Loss Detection Time Chart
PI output/SFS input
Sleep operation
level b5-15
Sleep operation
delay time
Operation
Operating
Fig 6.51 PI Sleep Time Chart
No Fbl
detection
Fbl detection
Loss detection time'
(b5-14)
Sleep operation
delay time
Stopped
Run command has been input
Operation status output
Time
, C2- ) is taken as sleep