Powerflex 525 control voltage 18 VAC

[heather.banks]

Hello All,
I am working with a powerflex 525 trying to get multiple speed references. I got it working on my bench and then I went out to the field only to find that the control voltage running the drive is 18 VAC. I can't seem to figure out where the 18 VAC is originating from. The drive start, stop, reverse, ect. is all controlled off of 18 VAC. I did not even think that it would work in this fashion. I was hoping someone could shed some light on this.

 

[alan_505]

I think the only way is to use relays driven by the 18vac and use the drives 24dc through the relay contacts.

 

[heather.banks]

So there are relays that pass the 18VAC we are using in the cabinet. The relay contacts on the drive measure 120 VAC. I don't see where we are going from 120 VAC to 18 VAC (it would be nice if we had electrical schematics for said machine). It almost seems like it has been wired wrong and something is shorting out and pulling down the voltage. In theory if we are using 18 VAC to start and stop the drive there should be some sort of device that changes that voltage right? Also terminals 11 and terminals 1 are still jumped together causing even more confusion. Terminal 11 is + 24 VDC correct? I really don't understand how these drives even start and stop properly.

 

[parky]

Two thoughts come to mind.
1. The 24v dc has bad capacitors so in effect you have rectified ac, a typical 24 v psu will give a reading of about that voltage, had one where a air blowing bottle line buildback was not working, the buildback was on a sensor plus timer, although monitoring the PLC the input showed true, the timer did not seem to time out, mesured the 24v DC supply & it was about 18 v in dc mode so thought it might need adjusting but could not as the adjustment pot was at full, I then noticed the Input card led's seem to be rather dim, checked with a scope & it was rectified AC i.e. pulsing at 100hz as the capacitors had completely dried out.
2. pickup of AC induced voltage, probably not as I would expect the DC side to be higher, but you never know.