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Andrius

PLC(FX3U)-inverter(D700) Modbus too slow connection

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Helllo, I have same problem, PLC FX3U and inverter D700 (5 inverters connected by modbus(using Function block Fr700fx)). For me need to stop motor at same place, by encoder, start using Function block ModbusFr700FXControl, and stop inverters time 0.0s (pr08 in inverter) but some time it stops at time (example if by encoder have 317 position it stops 325, but in second time it must stop at 317 it stops in 365). Maybe communication too slow stop in time (parameters in inverter for communication : Pr332-192; Pr334-2; Pr340-2; Pr539-5...) Anyone have any thoughts or experience to do that at the very least stopping distance would be equal? please help!!

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50Hz, stop command from Communication, Iverter after stop signal use DC brake, and stop time 0.0s(pr08) . Today test run signal from PLC output, better, but in test, same times it stops not in same place(I have same correction, too stop drive I have tested it's 33.0mm stop distance of line), like for example normal stops at 317.86 ir 316.98 but several times it stops 310.23 it's too much.. Why this happens? Edited by Andrius

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Dear, > increase the baudrate..... > change the DC bake related parameter i.e,Pr.10,11&12. > Use of brake resistor is advantage in ur application. > Use creep speed > Use high speed compare instruction in PLC and stop the drive through interupt generated by high speed comparison ins.

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Sorry for the late reply! Modbus is not preferred if you want the motor to stop on the same spot each time. This is very problematic when using 5 inverters, because the master (PLC) have to poll each inverter and the round-trip time will not be equal each time.... Use hard wires for start/stop.

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