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I am controlling the speed of my Altivar 61 or Altivar 71 drive with 4-20ma input. If this input signal were to fail for some reason, I need the drive to automatically switch to a secondary speed reference. How can I do this?
Altivar 61 / Altivar 71 series drives.
All models, All serial numbers.
The Loss of Follower function in the drive (LFF) only allows the motor to fall back to a fixed speed, or stop. It does not allow the drive to automatically switch to a secondary input.
We can configure the Altivar 61 or Altivar 71 series drives for this function under the following conditions:
1: There is at least 1 alarm group in the drive that is not being used. (The drive has 3 alarm groups which are unused in factory configuration)
2: There is at least 1 relay available. (The drive has 2 relays default, up to 2 more can be added by installing option cards VW3A3201 and/or VW3A3202. Up to 2 option cards can be installed on the drive but only one of each type).
3: There is at least 1 unused reference channel available (Reference channel 2, Reference channel 1B)
4: There is at least 1 unused logic input available on the drive.
If these conditions are met, we can make the following programming changes to the drive:
Under menu 1.5, select an unused Alarm Group and press Enter. Highlight parameter "AIX Ai 4-20" where X = the analog input for your 4-20ma input. Press Enter to place a check mark beside this. Scroll up and down to all other options under this alarm group and make sure that no other parameters have a check mark. We only want this alarm group to flag high if the 4-20ma input is lost.
Under menu 1.5, Select "RX configuration" where X = the number of an unused relay on the drive. (R1 is configured for fault indication from the factory) and assign this to "Alarm Group X" where X is the alarm group configured in the last step.
Install a jumper wire from +24 (0V terminal if the source/sink switch on the drive to the "C" terminal of the relay selected in the last step. Connect a jumper wire from the "A" terminal of this same relay to an unused logic input of the drive.
Select your unused reference channel on the drive and go to the menu location for this reference (Menu 1.6 for Reference 2 channel, Menu 1.7 for Reference 1B channel, either will work as long as it is not already being used).
Assign either "Reference 2 switching" or "Reference 1B switching", whichever you are using for this function, to the logic input that is now jumpered to the "C" terminal from the last step.
Assign either "Reference 2 channel" or "Reference 1B Channel", whichever you are using for this function, to the secondary speed reference you are using.
As an example:
I am bringing 4-20ma input in to AI2 terminal on my drive. If this signal is lost, I want my drive to automatically switch to a potentiometer speed reference I have wired into AI1 terminal. Under menu 1.6, I have Reference 1 channel set to AI2, my primary speed reference is this 4-20ma input on AI2 terminal.
Under menu 1.5, under Alarm Group 1, I place a check mark beside "AI2 Ai 4-20" and make sure that no other parameters have check marks beside them.
Also under menu 1.5, Under R2 configuration, I set R2 assignment to "Alarm Group 1".
I now place a jumper between +24 and R2C terminal, and another jumper between R2A and LI3 terminal.
Under menu 1.7, under sub-menu Reference Switching, I assign "Reference 1B Switching" to LI3 and Reference 1B Channel to AI1.
When my 4-20ma is lost on AI2, this sets alarm group 1 high. R2 then activates because it is triggered by this alarm group. When R2 activates, it connects +24 to LI3 terminal, pulling LI3 high. LI3 is assigned to Reference 1B switching to the drive is told to look at speed reference 1B. Reference 1B channel is AI1 where I have my potentiometer connected for speed control.
If the 4-20ma signal returns, the drive will automatically switch back to this speed reference as the alarm group is not longer set high, causing R2 to open, opening LI3 and causing the drive to switch back to its original speed reference, reference 1 channel, the 4-20ma signal on AI2.
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