Fault Relay concept in ABB VFDs

[Histor]

Hi,
In ABB ACH580 VFD drive we have output relay RO3 which I'm using for fault signal.
The relay got contact 25, 26 and 27 terminals. 25 and 26 are NC. 25 and 27 are NO.

I'm using fault(-1) option means inverted fault and they recommend to use NO terminal which is 25 and 27.

Im confused.

My understanding is that I have connected my external fault relay in 25 and 27 NO. The relay is energized normally when I power the VFD. So my NO become closed. And my external relay energized as well. When trip happens internally the internal relay trips and 25 and 27 become open (NO) again. My external relay de-energize.

Correct me if wrong

 

[che12345]

Histor (Electrical)(OP)3 Sep 24 02:18

' ABB ACH580 VFD drive we have output relay which I'm using for fault signal... I'm using fault(-1) option means inverted fault .. My understanding is that..'
I have the following suggestion for your consideration. Please check and verify whether in order.
1. The ABB manual states "default i/o connection, but does NOT elaborate on "Fault (-1) means inverted fault". This is the root cause.
2. I tried to look at it as following:
a) VFD off, contact (25-27) = Close. Please Check !,
b) VFD on, healthy, contact (25-27) = Open,
c) VFD on, faulty, contact (25-27) = Close,
d) VFD on, fault reset, contact (25-27) = Open,
Note: 1. When switching on the power, healthy condition, Contact (25-27) change over from Close to Open,
2. This means that switching off a healthy VFD, contact (25-27)= Close. This is going to indicate "Fault"? Check !
Che Kuan Yau (Singapore)

 

[jraef]

It's been years since I have programmed an ABB drive, but I believe you have that correct. In the "inverted" operating state (-1), the NO contact would be held closed when "normal" and drop out (open) when there is the fault that you programed it to.

As I recall though, when the drive is POWERED DOWN, and until it FINISHES powering up, that relay ALSO drops out. I recall this because it was something I hadn't considered when using it that way, so my SCADA system was getting a fault at least twice per day when they powered down, which in some cases when there were utility issues or safety shutdowns, filled the fault code buffer (that was a long time ago when that buffer only held the last 4 faults).Might not be a problem, but it's something to think about.


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