PTS Depression Controller

[Chad Speier]

I have been testings the new PTS Depression Controller for the last month. First, no issues. The unit is very easy to navigate and simple to hook up. The unit is used with a SCR and controlled by a POT. I can let Bruce explain things, but in a nutshell, you set the depression at your first lift increment and then run the valve down. The controller adjusts the depression!!!

Few pics.

[pablo]

Looks like you are controlling all the motors with the pot. Are you using just 1 SCR?? If so how many motors, 120 vac or 220 vac. in series.
What is amp rating of your SCR? Also have you checked the vacuum motors to see if they heatup at a low DP??
Bench looks good

[Chad Speier]

I have one 80amp SCR controlling 9) 240v Lighthouse motors. It doesn't get hot. I've used this bench daily since I built it in March. It's well documented on the old forum.

[pablo]

Yes I have seen your posts from the old forum. The HB Control tech told me the SCR's are all the same rating (90 amps), maybe more? That the size of the heat sink determines all the diff. Amp ratings.
I couldn't remember how many motors you were running but I thought that they were 240 VAC in series.
I also remember you saying that the heat from the SCR and heat sink was almost nothing.
I was just wondering if you were able to check the actual temp. of the motors when they are run at a lower speed, (lower DP). I was thinking that running all the motors at lower speed and with less of fan cooling effect might warm up the motor windings a bit. Just a thought.
I haven't decided if I'm going to control my motors (8 up to 12). I have 8 now in my bench.
Bruce was using the SCR to control just 2 motors and switching on more as needed for more DP.

[Chad Speier]

I have never even worried about the heat of the motors, I think it's a non-issue.

I just replaced my final 5) motors with new Lighthouse's. I can now pull 29" with my 2.500 hole on a 400cfm head. That same head with my 3.200 hole I can pull 40".

My motors are wired parallel.

[Tony]

Great to hear that you are happy with the results Chad.
Bruce was absolutely over the moon when he had the very first prototype up and running.

Pablo,
You definitely need to get an SCR power block big enough to do the job, then adequately cool it.

They are NOT all the same. The higher amperage rated units are much more beefy inside, even though they all look exactly the same on the outside.

Buy what you need. And for a heatsink, the rule of thumb, is that if you cannot place your finger on the heatsink and leave it there, it is far too hot. That might be roughly around 60C or 140F with all the controlled motors running absolutely flat out. But cooler than that is definitely better.

The more massive and over rated both the SCR power block (and heat sink) the more reliable it will be.

[pablo]

Tony,
Yeah, I get you on the heatsink/SCR. I was going to also use a small fan across the heat sink if it needed it. My cover on the bench over the wiring and relays is vented pretty good also.
I was just wondering if the vacuum motor windings heat up much at all when slowing them down to reduce DP. Probably not a big issue.
Also I'm getting some arcing/noise from mechanical relays when switched off. Wouldn't a RC circuit help with this. Vishay makes a simple RC snubber.

[Tony]

Anything that decreases motor power should not increase the motor temperature, even though the cooling airflow is less even with blocked flow.
After all, that is how normal vacuum cleaners are run, flat out with carpet usually blocking the airflow.

But Chinese made vacuum cleaner motors are rather cheap and nasty engineering, designed to a cost and to have a limited life span. So don't be too surprised if occasionally a motor spits the dummy.

You could try a series resistor/capacitor snubber network across the relay contacts, it certainly will not hurt.

Looking at it realistically, a higher amperage rated SCR power block may not cost very much more than a bunch of extra switches and relays. So why even bother switching motors manually ?

Just connect all the motors together up to Bruce's magic box, and let the PID control system do all the work.

[Brucepts]

I'm currently having a "PTS Next Generation" design 8 motor flowbench built by a local cabinet maker and plan on doing the wiring on this bench as a single controlled setup. This will allow me to actually do my own testing to answer some of these questions that arise.

My goal is to start selling complete PTS Flowbenches, separate parts (slider assembly) and possibly a kit that only requires the outside box construction. Working with the cabinet maker we are making changes to the design to allow for the "parts feature".

After I have the 8 motor bench done, he is going to build me a 12 motor bench so I can get that one tested in my shop and work any bugs out of it and refine that design.

Also currently working and on my bench right now is a 100" DM which will be offered in the near future.

Tony, would like to hear more about how to stop the arcing on my power relay contacts?

PS Sorry for the semi hijack on this thread . . .

[pablo]

Tony I already have the switches and contactor/relays setup and running my bench. Yes that was the plan to control all motors with the Bruces PTS motor controller. I agree it's the most sano way to go.
I'm just trying to get the wiring etc. laid out in my head. I have 8 motors now. So I'm figuring that I need at least a 80 amp rated HBcontrol SCR w/heat sink.
A conceptual/cartoon wiring diagram might help this old man here some. Block diagram etc.