ABB DCS 400 Analog input issues

I have a DCS 400 drive that is acting goofy. There is an eratic bouncing voltage in the neighborhood of +/- 1.5V on both AIN1 and AIN2, even with nothing hooked up to the inputs. I am trying to control it with an AB 1746 NIO4V analog card, with the card hooked up I get the same voltage fluctuations when outputting 0V on the card. Needless to say this doesn't work very good. When looking at the drive display it confirms what I am measuring with a meter, AIn1 actual is bouncing around up to 15% with nothing hooked up.

Any ideas what might be wrong? Bad power supply, faulty opto isolators on the drive, something else?

I hate to have to tell you this but the DCS400 has been an embarrassment for ABB from the day it was first released. "Acting goofy" about sums it up.

My recommendation, seriously, is to dump it and replace it with a good drive. Fixing the current problem with the Analog Inputs will only open the door to further problems. In addition, that drive is likely approaching 10 years old so it is pretty well "used up" anyway.

As much as I like ABB, for DC I tend to use Bardac. The product is bulletproof and the tech support is superior to any one else I've worked with.

DickDV said:

I hate to have to tell you this but the DCS400 has been an embarrassment for ABB from the day it was first released. "Acting goofy" about sums it up.

My recommendation, seriously, is to dump it and replace it with a good drive. Fixing the current problem with the Analog Inputs will only open the door to further problems. In addition, that drive is likely approaching 10 years old so it is pretty well "used up" anyway.

As much as I like ABB, for DC I tend to use Bardac. The product is bulletproof and the tech support is superior to any one else I've worked with.

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Thank you for the honest opinion, I was hoping you would respond. We inherited this drive from a sister plant about 3 years ago and to be honest I haven't been real impressed since we got it although this is a new problem. It is a very low performance application so believe it or not even with this problem it still works, just not very well. I have used many ABB AC drives in the past and have been very impressed with them.

My counterpart wants to install an isolator on the input to just see what happens, I think if that doesn't do it then out it comes. It's a 250HP drive though so it's not an off the cuff decision.

Our plant standardized on Eurotherm/SSD/Parker many years ago so that is what it will be replaced with. The drives have been very reliable, are very flexible as far as programming, and their service is good. We probably have 50 or so DC drives and well over 150 AC drives from them and are quite happy.

Thanks again.