# VFD Issue: ABB ACH550



## erics37 (May 7, 2009)

Can you run it in Local mode from the keypad?


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## mollydog (Jan 9, 2009)

*Variable frequency drives*

Wow....... You are saying that there is Alternating current out-putting where direct current should be?

Two went down and all parameters are saying all is well ?

without being there maybe a PLC (programming problem)
two together, rule out PCB cards.

Can you give us more info, like how are they connected, there is power to both, what motors they serve and how they are turned on? Like from the PLC or some other device.

Don't rule out a limit switch some where. Jim


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## sparkywannabee (Jan 29, 2013)

Have you checked some random parameters against your parameter list to make sure a surge of some kind did not wipe parameter file clean.


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## John Valdes (May 17, 2007)

Zana said:


> So, peculiar case I have today. Had two ACH500s 'go down' at the same time. Thing is, the VFDs aren't reporting any sort of faults but just seem to be sitting there waiting for something. We had Siemens come by and check their BAS system, but of course the drives are still being blamed.
> 
> During some testing, I noticed the control cards seem to be outputting 5 VAC to the customer connections, even the one obviously labeled '24 VDC'. Anyone know what could cause this issue? The VFDs are powering on normally (no faults), so the circuit cards are getting the required voltage to turn on properly, but AC coming out of an obvious DC output is never a good thing.
> 
> The VFDs are ignoring the commands sent from the Siemen's control panel and won't power up the motors they're connected to.


Like Eric suggested. Will they run in local mode? If so, the drives are sitting there waiting for a command.

What command does the Siemens controller send to the drives?
Find out what type of command it is and make sure it is present when the Siemens controller is telling them to start.

Go to your parameters and see what operational mode this drive is set up for.
No fault and idle drives tell me the drive is waiting for you or the Siemens controller.


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## oliquir (Jan 13, 2011)

pretty sure they sent wrong voltage into the abb pcb and now pcb are gone.
try them in local mode, if it works, try them in remote but disconnect all wiring from siemens control panel and measure if 24vdc is now ok


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## JRaef (Mar 23, 2009)

Generally, "control boards" in a drive do not PRODUCE power, they are looking for changes to take place in a circuit, i.e. contact closures and resistance changes for inputs, or the CONTROL of external power from somewhere else, as is the case on outputs. SOMETIMES the drives will have a SMALL amount of output power available, say for driving an analog output for example. But you should NEVER try to use that to drive anything else, it will not have sufficient power to do something like, for example, turn on a DC relay coil. So if someone failed to read the manual WARNING them not to try to do that, you may have blown the power supply board. If you are lucky, maybe it just went into current limit to protect itself and has not fried.

So go back and THOROUGHLY read the manual and understand what it is you are looking at, and what the limitations are, then compare that to the BAS wiring that Siemens did. You might find that they got lazy and rather than put in their own 24VDC power supply, they tried to tap off of the on-board power supply, which cannot handle the load they are trying to draw from it.

By the way, this is a VERY common problem with HVAC guys.


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## JRaef (Mar 23, 2009)

A quick look at the manual shows that terminal 7 on the control card is a 24VDC supply, but is limited to 200mA maximum, basically enough to drive a couple of pilot light bulbs. There is another 24VDC supply at terminal 10 for use with the digital input devices, i.e. contact closures. That is limited to 10mA!

Also, if you are reading an AC signal on the DC input wiring, that may indicate that nobody took the requirement for shielding the input conductors seriously, and/or some are run in parallel with AC conductors instead of crossing them at right angles, so you are getting induced voltages on the inputs and confusing the heck out of the VFD, if not damaging it.


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