Danfoss VLT FC 280 Operating Manual page 66

VLT® Midi Drive FC 280
Operating Guide
The correctness of drive's iParameter must be ensured by user via commissioning test.
Table 32: Non-editable F-parameters
Parameter Value
F check iPar 0 = NoCheck
F CRC length 0 = 3 or 4 bytes CRC
F block ID 1 = F iPar CRC within F parameter block
F Par version 1 = V2 Mode
F SIL 8 = SIL3
It depends on PROFIsafe version: V2.4, 3 bytes CRC; V2.6, 4 bytes CRC.
1
6.5.2.3 PROFIsafe Watchdog Time
Use the F-parameter watchdog time (F WD time) to determine a watchdog time for the communication between F-host and F-de-
vice.
The minimum watchdog time has 4 parts:
• DAT = Device Acknowledgment Time. The F-device receives a frame, processes it, and prepares a new frame to send.
• Bus = the transfer time of the frame from the AC drive to F-host.
• HAT = Host Acknowledgment Time. F-host receives a frame, processes it, and generates a new frame.
• Bus = the transfer time of the frame from F-host to the AC drive.
DAT Bus
Illustration 37: PROFIsafe Watchdog Time
Sometimes, it is difficult to determine the bus transfer time that is used to calculate the watchdog time. For more information on
the cycle times, see the user manuals of the specific fieldbus.
The F WD time can be calculated via the following formula:
F WD Time = DAT + HAT + 2 × BT
Table 33: Description of the Parts of the Watchdog Time
Symbol Name
DAT Device Acknowledgment Time
HAT Host Acknowledgment Time
BT Bus Cycle Time
The F-parameter F WD time must have a value that is slightly greater than the sum of DAT, HAT, and 2 times the bus transfer time. It
is recommended not to exceed the calculated value by more than 30%. Setting a shorter watchdog time does not have an effect on
the safety of a system, but it can cause a fault and make the AC drive trip. For example, if HAT is 4 ms and the PROFINET cycle time is
4 ms, F WD time should be set to:
F WD Time = DAT + HAT + 2 × BT × 1.3 = 70 ms + 4 ms + 2 × 4 ms × 1.3 = 110 ms
66 | Danfoss A/S © 2022.02
N O T I C E
(1)
F WD Time (minimum)
HAT
Unit Description
Manufacturer-specific iPar check.
CRC2 signature length.
Parameter block type identification.
Version no. of F parameters.
Employed SIL level of F-device.
Bus
Description
70 ms for the complete AC drive system.
Application-specific.
The bus cycle time.
AQ381425076031en-000101 / 130R1223
Safety Functions