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Contributor

Re: CDVR voltage setpoint keeps changing..

MikeL, as you said, the synchroniser is connected to the rise and lower terminals. see picture of connection drawing.

I guess we need a unit that gives out an analog singnal ranging from 0 to +/-10VDC, is that correct?

but what if the voltage the synchroniser is trying to match is more or less than 10% of the generator voltage?

IMG_20170925_113401.jpg

 

 

Contributor

Re: CDVR voltage setpoint keeps changing..

I understand now, thank you. Tomorrow I will provide you with more information about the synchroniser and how it is wired to the CDVR. 

Super Contributor

Re: CDVR voltage setpoint keeps changing..

The auxiliary input provides a temporary bias to the voltage setpoint, once the auxiliary input goes back to 0 VDC, the original setpoint is used. When you use the RAISE/LOWER inputs, you actually change the setpoint, and it retains that setting even after the units shuts off and strats back up again.

 

Most newer synchronizers have the option to use raise/lower contacts or an analog output, can usually be either a voltage or current.  Plus or minus 10VDC on the aux input should change the voltage 10% (if the Voltage Adjustment Band on the Setpoint tab of the CDVR software is set for 10%, usually the default), so if you apply a positive 1VDC to the aux input, the voltage should raise 1% of the setpoint.

 

If you provide more info on your synchronizer I may be able to tell you if it can provide a suitable signal for the aux input.

 

MikeL

Contributor

Re: CDVR voltage setpoint keeps changing..

I am not currently at work but I will check how the synchroniser connected to the CDVR tomorrow. If it's connected to P9-4 and P9-5 like you said, how can it be changed to P12-3 and P12-6. what kind of input do these terminals take? in the manual it says +/- 10DCV but how would that change the generator output voltage?

Super Contributor

Re: CDVR voltage setpoint keeps changing..

So how do you have the synchronizer interconnected to the CDVR?  Since you appeart to be changing the setpoint I'm assuming you have raise and lower contacts from the synchronizer that are wired into P9-4 (LOWER) and P9-5 (RAISE) with the common on P9-6, is this correct?

 

What kind of synchronizer are you using? Does it have an analog output? What kind? 

 

MikeL.

Contributor

Re: CDVR voltage setpoint keeps changing..

Yes I have the manual

Super Contributor

Re: CDVR voltage setpoint keeps changing..

Do you have a CDVR manual?  Would be helpful and I can point you to the areas in the book I am trying to explain

 

MikeL.

Contributor

Re: CDVR voltage setpoint keeps changing..

Hello MikeL, thanks for replying.

can you explain further with more details please, I still don't have a lot of experience  with CDVR.

THANK YOU.

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Super Contributor

Re: CDVR voltage setpoint keeps changing..

How is your synchronizer voltage adjust wired to your CDVR?

 

If you are using the Raise/Lower inputs then you are changing the speed reference setpoint, and it stays where it gets left. You should be using the +/- 10 VDC input to bias the CDVR for synchronizing or paralleling (if using active VAR Control), when this signal returns to zero volts the voltage setpoint remains where it was set.

 

MikeL

Contributor

CDVR voltage setpoint keeps changing..

Hello guys.

I have got 4 1MW generators as standby supply of an oil refinery. AVR is CDVR which modified through CDVR software. There are setup to work parallel and synchronise with the main grid. When the main grid fails, the generators automatically start and take the load, and when the main grid is live again, a manual change is required and the generators synchronise with the grid first before changing the load to the main grid and they then shut off. 

Well the problem is, the grid voltage is very unstable and ranges from 400 to 440v throughout the year depending on the season. Rated voltage is 415v. The AVR setpoint is set on 415v initially but when the generators try to synchronise with the grid and change the output voltage either up or down, the setpoint changes too and it remains on the new value. For example if there was a power failure and the generators start up at 415v (initially set) and after sometimes the main power grid is back but with a voltage of 430v the generators will change the output voltage along with the setpoint to 430v and then shut off. Now the next time the gird fails, the generators start up with a voltage of 430v because the AVR setpoint is changed.

how do I prevent that from happening? Or the software is designed like this?. I want the generator to synchronise with the grid whatever the voltage was, but I also want the AVR setpoint to be fixed so the next time there's a power failure, the generators voltage would be 415v.