Valve Control with VSD

Noted. And we have already communicated this to customer, but thank you for the confirmation.
 
boneless said:
Noted. And we have already communicated this to customer, but thank you for the confirmation.
Click to expand...

You're welcome.
Please note that all control application that I've seen use SAR drive with AUMA MATIC controls and wiring diagram as shown in attachment. Of course this is in case when no positioner is used and there is no current control signal, only 24 V DC commands.
 
from my own experience, if its "not fit for purpose" then you will waste time and money doing a compromise and it will forever haunt you and eventually you will change it out.


just do it right first time around.


i use this saying "i have time to do it right, but don't have time to do it again"
 
1) I believe some Auma valves have DC motors, and that is how they can adjust travel speed. The three-phase supply is rectified within the actuator. Verify this with your supplier.

2) I have controlled many many Auma valves with direct control using a reversing contactor. I use this in flow control applications all the time.

3) What will a VFD do for you? Set the travel speed at the actuator, and then use a reversing contactor to move.

BFV.JPG
 
Hi Tom,


I am pretty sure it is a 3 phase motor, just by looking at the supplied wiring diagrams, I may be wrong.


We will use two of these valves to control the temperature through a heat exchange. One valve for through flow, one for bypass, their opening is reversed. So 0% on 1, will give 100% on 2, to maintain a stable pressure drop.
From experience, the valve is adjusting a lot.



All in all, from the responses in this thread, I feel we are right to demand our customer to supply the correct valve. Anything else will very likely result in massive headaches and sub-optimal performance.
 
What you are describing doing is, in the worst case, to create a servo positioning control using a VFD. That is not as easy as it sounds with a feedback loop consisting of a pot like that. Most inexpensive VFDs are not really capable of positioning control at all, those that are will not be inexpensive and will want an encoder or resolver as the feedback.

About the best you could hope for is to emulate the "bang-bang" positioning that you would have with contactors, except do it electronically using the VFD's inherent soft starting (with full torque) and electronic reversing capabilities. If that's good enough, then it should not be too hard. I've done it with small cheap VFDs, the most difficult aspect is managing the expectations of the end user.
 
Hello again,


jraef, thank you, I think that answers the question for me. It is possible, but you shouldn't. It won't be any better than using contactors.



g, they are not too big, 400VAC/0.1kW.
 
boneless said:
Hello again,


jraef, thank you, I think that answers the question for me. It is possible, but you shouldn't. It won't be any better than using contactors.



g, they are not too big, 400VAC/0.1kW.
Click to expand...
They are, in my opinion, actually slightly better than doing it with contactors in that there is no torque surge when banged on with a contactor, so the valve lasts longer and there are no contacts to burn out and / or weld.
 
EICS said:
from my own experience, if its "not fit for purpose" then you will waste time and money doing a compromise and it will forever haunt you and eventually you will change it out.


just do it right first time around.


i use this saying "i have time to do it right, but don't have time to do it again"
Click to expand...

Best advice so far.
 
I totally agree, but sometimes our hands get tied. In this instance, we have a customer that orders the wrong parts, and can not or will not rectify. There is a huge language barrier as well.


I was just brainstorming some possibilities, because it is not unlikely that things are unchanged when I arrive onsite in 6 months to do commissioning. We have put the ball in their corner, and it has been quiet for weeks. We will see how this ends up :).


Thank you everyone for the valuable input.
 
boneless said:
Hi guys,


Yes I know the AUMA supplied positioners, they are great. My customer "forgot" to order them with the valves. So all we have is a valve, with a 3 phase motor, position feed back, and limit switches.



They do not seem to understand the issue, we have told them to return the units to AUMA and let them add whatever they need to make it suitable for our system.



So I am just brain storming possible solutions here, my idea for using a VSD is to be able to slowly jog the valve motor, in either direction, using the pot meter as feedback.

We have done this with contactor based motor reversing, but it has shown to be pretty hard on the system.


So, again, the thought just crossed my mind and I was wondering if any of you has done it this way before.


Thanks again!!!!
Click to expand...


You need to program 3 step control to PLC, soe PLCs have build in block for that.


Wire posiotion feed back to AI (either Volts or 4-20mA),


Then on program side compare if feedback from pot is outside of your 0..100% controlsignal or inside control hysteresis.


With compare result control 2 DQ outputs on CPU, which drive contactors.
You need probably to pulse outputs, so that valve won't drive too fast either.
Problem can be that valve actuator is designed only to full close / Full open control, not to continuos control if mA control is missing.
 

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