motor controller option?

[bruce]

I think you will find two "camps" on motor control . . . those that think they need it and those who know they do not. I personally have no clue if I need it or not

I've talked to various levels of flowbench users and find that most do not want it and want to know and see when the static pressure changes. The ones doing individual port development work do not need it (they want to see the static change when they are port probing) and the ones just measuring CFM for customer heads would like it to speed up production to increase profit margin.

Is it a possible future project? Yes, it could be we just have to find all the bits and pieces that make it possible as Tony suggested above. It's not a front burner project though I'll say that much as I feel the demand is quite low. I may be wrong in this assumption?

If we do develop something it will work with the existing base of PTS DM's already out in the field so nobody will need to send it back to the "factory" for any upgrades.

One problem I have in new product development is the initial cash outlay, I have kept the prices of all my products at a level the average person can afford so I do not have a large profit margin to dump into new product development. Probably a poor business model on my part but that's the way I'm running PTS.

Right now Rick is in a somewhat major upgrade to FlowSoft Basic and we want to get Larry back online with his excellent FlowSoft Excel product to compliment the existing PTS DM customer base.

[Tony]

Right now if someone wanted automatic test pressure correction desperately enough, there is one (almost) off the shelf solution.

The better quality variable frequency drives now all have the required closed loop control features already there in software. It is just a case of selecting the required parameters from a pull down menu when programming the unit initially to set it up to do what you want.

In other words, they already have an internal PI or PID software controller, and all you need do is fit an external pressure transducer to measure test pressure, and a control potentiometer to the VFD.
It will then correct motor speed to hold the voltage from the pressure transducer to whatever voltage the external potentiometer is set to.

This is a fairly common requirement for commercial VFDs used in industry, to hold "something" constant by correcting the motor rpm up and down as required.

The only real problems I can anticipate are that a particular VFD may not get along too happily with some particular brush type vacuum motors. There may be no problems at all, no way of really knowing for sure until you actually try it.

But it will certainly work very well indeed with a three phase induction motor for which a VFD is really designed, and a single large air blower.

If you already have the speed control potentiometer, VFD, and blower hooked up to your bench, the only extra needed for fully automatic test pressure control, would be a second dc input voltage to the VFD corresponding to test pressure, and enable the internal closed loop controller that may already be there.