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 Fluctuating Motor speed 
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Joined: Fri Jan 08, 2010 3:35 pm
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Location: Pennsylvania
damunk wrote:
I wonder what motors 'commercial air flow bench" use?


Pretty much the same as we are using in the DIY bench or even cheaper quality.

You would actually be surprised/shocked seeing the inside of a Commercial Flowbench

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Bruce

Who . . . me? I stayed at a Holiday in Express . . .

Charter Member of the "Society of Open-End Wrench Users"


Mon Aug 28, 2017 9:09 pm
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Joined: Fri Aug 26, 2016 7:08 pm
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Anybody got pics of the SF machines. Would like to see them.


Tue Aug 29, 2017 11:36 am
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Joined: Sat Oct 03, 2015 1:38 pm
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Good grief, Those UPS machines are expensive. Especially if you need three of them to spread the load across separate power sockets to prevent overloading.


However I think I have another way of solving this problem :)

Pick a voltage (i.e 235V) and take the measurement when the voltage is at 235V. :) Simples ?

So now if all three motors are running I need some sort of voltage reading device to add all the voltages together and divide by 3 to get the average figure and to be able to DISPLAY THIS VOLTAGE READING.

Now if you take the manometer reading every time the voltage is at 235V then job sorted. What do you think?


Tue Aug 29, 2017 5:03 pm
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Joined: Wed Mar 03, 2010 3:40 pm
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Location: Melbourne, Australia
There is another insidious problem you may not have thought of.
Motor winding temperature.

As the copper windings heat up (or cool down) their resistance changes significantly, and so does the motor current. There is a complex mixture of motor voltage, cooling air volume through the motors, and motor rpm that is almost constantly changing. If you feed a fixed voltage to your flow bench, it can take quite a long time for absolutely stable flow to be established.

You will notice that when you set test pressure manually, it will always slowly creep. You cannot set it, walk away from the bench and come back ten minutes later and expect to see the exact same test pressure, it always wanders. If the mains voltage is also constantly changing, it will be an exercise in frustration.

A fixed constant motor supply voltage is not as useful as you might suppose.

A fixed and constant bench test pressure is what you should be aiming to have.

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Tue Aug 29, 2017 5:53 pm
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Dear God. Already spent and design the box but now a redesign required because this is a major flaw.


Tue Aug 29, 2017 6:00 pm
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Joined: Sat Oct 03, 2015 1:38 pm
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http://www.flowbenchtech.com/motorcontrol.html

If this is what your talking about then can it allow 3 motors to connect to it as I understand this unit can control the motor speed?


My three motors must run on separate power sockets on the walls to prevent overload.


Tue Aug 29, 2017 6:15 pm
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Joined: Wed Mar 03, 2010 3:40 pm
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Location: Melbourne, Australia
Yes, that is it.

If your three power points are all running off the same phase, which seems likely, you can use one power control module to run as many motors as you have, and speed control all of them together. This is the best and most convenient way, as you then have seamless speed control from zero to flat out.

Just tell Bruce what your total combined motor current is, and he can supply what you need to do that at a price you will not better anywhere else.
One of Bruce's power control module could potentially control up to a hundred amps if you need it, so current capacity is never a problem.

Put the three power controllers you already have up for sale on e-bay.

That is the first step. You can use that with a ten turn manual motor speed control knob to get you started at minimal cost.

The next step up from that is to fit the automatic pressure controller. This measures the bench test pressure via an air line and automatically adjusts motor speed to keep bench pressure constant at whatever you set the pressure control knob to. The idea here is to disconnect the control potentiometer that controls the power module, and connect the automatic controller in its place.

That cannot be done with the three controllers you already have unfortunately. The controller Bruce supplies has a microprocessor and a fully isolated input voltage. The potentiometers in your existing controllers will be connected directly to one side of the mains, and the wiring inside the controller is all "alive" so cannot be extended for external control.

The constant pressure controller also works as you make flow measurements at different valve lifts. The motor speed self adjusts at every lift increment to hold the test pressure constant. It not only vastly speeds up testing, your final figures will be more repeatable because there is a minimal change in test pressure from reading to reading. Once you have used this, you will never ever go back to manually adjusting test pressure. Its that good !

This is now a very well proven system used by a great many members of this Forum.

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Tue Aug 29, 2017 6:44 pm
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There are a reported 20,000 fires in the home each year in the UK. Fires that claim the lives of between 60 to 70 people, and a further quarter of a million injured.

That's why I want to spread the load. :)

Attachment:
motors.jpg



My understanding is the three motors connect to PTS SSR Motor Control. But where does the PTS SSR Motor Control connect to? only one power socket? UK double socket can handle 20AMP but have to use both socket. A UK single socket rated for 13AMP so means have to use atleast two sockets.

On the ametek 119996-00 motor it says 240V 5 AMP.


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Tue Aug 29, 2017 7:11 pm
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Joined: Wed Mar 03, 2010 3:40 pm
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Location: Melbourne, Australia
I am in Australia, so have very little knowledge of the UK wiring system.
What kind of plug would a 30 amp single phase welder have in the UK ?

In Australia we have a three pin 32 amp plug/socket available.
http://www.electriciansupplies.com.au/shop/index.php?main_page=product_info&cPath=566_20_135&products_id=2712

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Tue Aug 29, 2017 8:16 pm
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Joined: Fri Aug 26, 2016 7:08 pm
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Do they have power conditioners for 220-240v. They are available for 110v but I dont remember how big of a load they will carry. We used them in a recording studio.


Wed Aug 30, 2017 9:50 pm
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