new aussie member with a few Q's

[106-1194218389]

If I was to tap into the very bottom of the chamber below the test orifice, the chamber the vacuum source is in would that show me the total depression the motors were pulling? It would be like the test pressure tap but on the opposite end. Shouldn't that then give me the total depression the source is having to pull? Do you guys think that would work?

John

[Tony]

Yes it would.

[FPV_GTp]

Hi

What speed_controllers are you using for the vacuum motor ?

Do you have a website link for a any particlur band of speed controller 240Volts ?

cheers

[106-1194218389]

There was a thread on this forum that discussed that, power controllers. I will see if I can find it. The ones they were showing were out of Germany and I thin they were Kemo brand - they were nice

John

[Tony]

Just make sure that whatever you use is designed for motor speed control, light dimmers are NOT suitable.

Read the specifications very carefully.
If it mentions incandescent lamps, or non inductive loads it is NOT suitable.

If it says suitable for inductive loads or motor speed control, that is what you want to see.
And it will definitely say that somewhere in the advertising small print.

The difference is rather difficult to explain simply, but it has to do with motors producing their own high voltages, and sparking at the commutator. The el-cheapo light dimmers either go completely nuts, don't control properly, or blow up fairly quickly. Or all three !!

[larrycavan]

Welcome to the forum

[FPV_GTp]

[bruce]

The plans ease about 95% of the design challenges, orifice style would be my choice now that I built one

I'm trying to find a way to ease the pain of the economy on everyone that is interested in building a bench. One dilemma is, I've sold plans at the current price so dropping the price would not be fair to those people. I'm toying with the idea of offering a discount on other products I sell specifically a discount on the new PTS Digital Manometer when it comes on the market. I think this might ease the pain some and make the plans more attractive to those on the edge but just not sure? The discount would also apply to people who already purchased a set of plans. The digital manometer is already going to be a deal over any of the other commercial products already on the market, thanks to forum support in it's design.

[FPV_GTp]

[bruce]

I did not take it as whining. Your post merely offered me the opportunity to propose what I have been thinking over for the past few weeks. I just have not come up with a good solution

[jsa]

[Tony]

Hi John, I am from sunny Melbourne.

Yes, finding a blower motor speed control sure isn't always as easy as it appears.

The simplest off the shelf solution is a variable frequency drive, with inbuilt PID controller, exactly as you suggest. These start out at around a thousand dollars, so it is certainly not a low cost solution, but it is what I am using with my large induction motor.

A big variac is entirely practical for manual motor speed control, and it has the advantage of being indestructible. Anything electronic will self destruct when a motor fails, as they invariably do. Killing a twenty dollar Chinese router speed control module is one thing. Blowing up a good thousand dollar VFD is something else. So a variac has the big virtue of surviving motor catastrophes.

I cannot find anything suitable here in Australia either, in the way of a simple low cost motor speed control module with isolated voltage control input. There is also the problem of 120/240 volts and 50/60 Hz, so buying things in from overseas should be treated with great caution.

Whatever is used for mains phase control must use back to back SCRs and not a Triac, which is what most of the low cost lamp dimmers use.

The whole thing is fraught with difficulty, especially in oZ.

My own bench uses a single large industrial centrifugal blower, powered by a three phase induction motor and VFD.

Vacuum cleaner motors are simpler, but finding a way to control their speed electrically may not be that easy in some countries.

[106-1194218389]

This was posted one time and I thought it would be an ideal speed controller. The only place I could find this though was out of Germany and shipping was costly. I could not find any in stock here in the USA. If anybody knows of any here let me know please.

John

[jsa]

[Tony]

The Kemo module is ideal, and it also has an additional isolation module you can buy that goes with it, which means the motor speed control will be via a proportional dc voltage completely mains isolated. Sadly both modules ain't exactly cheap.

Yes I realize a variac is only suitable for vacuum cleaner motors, but that is what we are discussing here. Personally I hate vacuum cleaner motors, which is why I run a single 10 Hp induction motor. More air for less amps, and vastly less noise.

The Aussie dollar will likely now stay down for many months, and will probably drop even lower.
The global financial, and stock market crash that is unfolding right now, I have been anticipating for a very long time.
If you own gold or silver bullion, or gold/silver mining shares you will prosper, otherwise it is going to be a grim nail biting period leading to total ruin for most investors.