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Variable frequency drive control via Modbus, register read/write limit?
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V_King:
Hello,
I am after variable frequency drive, to control the electric motor RPM via RS485(Modbus).
There is a Bosch Rexroth EFC5610 VFD, which I really like, it has an in-build motor thermal protection, but in Modbus communication description it warns that the registers read/write limit is only 150000 times/register. I will be changing the frequency registers frequently and that worries me.
I had a look at other VFDs (Siemens V20, Schneider ATV12, Parker AC10) and none of their manuals mention the Modbus communication limits for read/write cycles per register.
A lot of the industrial electronics seem to have unwritten defaults and I wonder whether the 150k cycles mentioned by Bosch is default for majority of VFDs, or is it just the big drawback of the EFC5610 VFD?
Thanks
Kalin:
I have never hear of that with other drives and never run into a failure to write to memory with any drives I have used even the ones that use an eeprom for storing parameters. How often do you plan on writing to this value?
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V_King:
--- Quote from: Kalin on March 03, 2019, 05:35:30 pm ---... How often do you plan on writing to this value?
--- End quote ---
The motor is for a small test rig, to test parts. The test would use up to 10 different frequencies (not pre-set ones). The test could be run to to ten times an hour, 8 hours a day. So pretty much in theory, the registers would be shot within a year :(
I would have thought the read/write count would be much greater, considering todays interconnected controls in the industrial environment.
Kalin:
Would you consider another manufacturer or have you already purchased the drives? It might be a typo because that is not really an acceptable number for any application I can imagine for a VFD.
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V_King:
--- Quote from: Kalin on March 03, 2019, 08:56:58 pm ---Would you consider another manufacturer or have you already purchased the drives? It might be a typo because that is not really an acceptable number for any application I can imagine for a VFD.
--- End quote ---
I was not far from placing the order, luckily found the info in time. I just wanted to make sure it does not apply universally throughout VFDs before considering different manufacturer.
I do not think it is a typo, because the read/write limit is throughout a number of revisions I checked and they have warning in a number of manual sections.
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