Depression control via motor speed?

[Jesse Lackman]

Ah, here is how you do it;



Input: 120 VAC, 50/60 Hz, Single Phase
Output: 120 VAC, 41.6 A, 5000W max
Travel Time: 19 Seconds

Cool.

[gofaster]

Jesse expressed some confusion about air watts. I did some checking on the subject a few months ago because I was having a problem understanding the differences between the many available vacmotors.
Here is a link to that thread:



Hope it helps

[84-1074663779]

[86rocco]

Well, I picked up my variac today, did a few very non-scientific tests with it using a shop vac. My first impression is that it seems to order a very nice level of control. Over the next few months, I'll build my bench, that'll be the real test. I'll keep you posted.

[Jesse Lackman]

Any ideas how to ship these to the US from Guam?



I'm getting some quotes, just for fun I'm sure.

[86rocco]

Shipping from Guam huh, could be pricey! The one I've got is 0-140 VAC, 3.0kva output, maximum 20 input amps, it's pretty big, it weighs 18 Kgs. I was lucky, I got mine off of eBay from someone local to me so I was able to pick it up. I plan to mount mine in the back of my bench and add an extension to the shaft so I can put the control on the front side.

[84-1133470038]

Back again ! I have had trouble accessing the Forum.

Terry is right about being able to automatically control test pressure with motor speed, and some negative feedback, it can be done.

What would be needed is a pressure transducer to measure test pressure, a PID controller and, a motor driven variac. The difficulty would be to tune the PID controller properly so it has good control dynamics over a wide operating flow range. It can be very easy to end up with something that is either very sluggish, or becomes unstable and hunts under certain conditions.

I have had some personal experience tuning PID (proportional, integral, derivative) feedback loops, and know it can sometimes be rather tricky. But it should be possible.