PTS Flowbench Forum

Hello all I'm new here..just doing as much research as I can. I already have everything I need to build an ssr motor controller including the 240vac to 24vac transformer. My problem is that in all my searching I have only found suitable random fire ssr's in the 3-32vdc input range. Every 5-24vdc input ssr I can find is zero crossing. It seems that when applying only 24vdc to a 32vdc max gate that the motors will never see full 240vac. Is this correct? If so does anyone know of a manufacturer of 24vdc max gate random fire ssr's? Thank you in advance...

You need a Phase Angle Control Module

Brucepts wrote:You need a Phase Angle Control Module

I have the SSRMAN-1P. Maybe I don't understand the phase angle control well enough...does it step up voltage?

Hey Fatts, welcome to the forum.

Its good to research, but many before you have done the hard work. There's a few that sort of work but there's only one that has been researched, developed and built for flowbenches.

The PTS phase angle control solves all your questions and comes with a ten turn pot so its super easy to use and target depression.

Bruce has videos of it working, here's mine manually adjusting and targeting at 60". Takes less than a minute from a standing start

https://www.youtube.com/watch?v=3Y3eirooGpA

Jim

Fatts250 wrote:Maybe I don't understand the phase angle control well enough...does it step up voltage?

Other guys on here can explain it in more depth than me, but I've looked at quite a few set ups and this one kicks ass.
Adjustable solid state relay with a ten turn potentiometer. It just varies the power to your motors from the main power source. Little cool extras like soft start, already heat sink mounted. 2 wires from the pot, 2 wires from 24 volt transformer and 2 wires for main power in and out. Fit it up and away you go flowbenching.

Jim

I will try to explain with pictures and some, but Tony will probably chime in and correct my misgivings. The phase angle controller does exactly that it varies the power output of the non latching SSR by triggering where in the power cycle of the sine wave you have adjusted input trigger too thus controlling where the phase of the output signal/power begins.

Picture the SSRMAN module almost like carburetor on a small engine if we remove it and put fuel in the throat it will run but only at max speed, if we limit the air and fuel we limit the motor speed and output power.

Phase Angle, If you understand that AC (Alternating Current) works in manor where it changes polarity +- -+ +- -+ continually at your countries power frequency 50Hz or 60Hz in other word it changes polarity 50 to 60 times a second. This polarity change does not happen instantaneously it ramps up and ramps down 0 Volts to Peak Volts to 0 Volts and so on. This can be seen in the picture below in blue. Phase angle interrupts this process and begins/triggers the power to come on at some given point in the cycle as seen in the picture in black 50%. So if we now look at the sign wave of AC as a 0% to 100% to 0% to 100% cycle of power we can see that if we could so smartly turn the switch on so to pick up the power at 50% after peak and keep it to 50% before peak on the alternate phase we would limit the power out to 50%, this particular factor (when it knows to trigger) is why your phase angle controller control transformer MUST be wired in phase with the power source being controlled. Your tuning the POT is only telling the controller where in the phase we should start and stop.

I think what confuses people more is that often one thinks of electricity in the form of DC or even common plumbing thus they think "Oh I can just pinch the hose and limit the power flow!" but AC phase angle does not work like that it does not dump excess power to heat it only gives you what you ask for up to its limit.

The voltages that you are discussing on a random fire SSR if I am not mistaken are the range that is minimum to maximum of what working trigger voltage they will operate on I/E the switching voltage ON/Off not off to full power, if this SSR could do this why would we need the SSRMAN module. Yes I know there are some out there like this but they are cheep and used mostly for resistive loads.

Hope this helps.

Rick.

Rick thank you for the detailed explanation. I was under the impression that the rheostat varied voltage to the ssr gate. I have more learning to do

Hi Fatts, welcome to the Forum.

As Rick says, the input voltage to the SSR is a train of pulses that fire the SSR at the right instant in time.

This requires an electronic control circuit board (that contains a microprocessor) that goes between the potentiometer and the SSR. And this needs a 24v transformer for both power and to get timing information from the mains.

While you can hunt around and source all the individual parts to do this yourself, its much easier to just order what you need from Bruce.
You then know for sure you have the correct parts, and you may even save a few dollars that way.

What you will need:

A random fire SSR of suitably high current rating. (Bruce or e-bay)
A heat sink depending on current through SSR (Bruce, or a do it yourself flat sheet of 3mm aluminium)
For Australia, 240v to 24v 50Hz small transformer (best bought locally)
Electronic control circuit board (Bruce)
Ten turn potentiometer and suitably large knob (Bruce or e-bay)

Hi fatts Welcome...
Guy for a long time I studied about it, and came to the conclusion than mount the SSR over the controller and cheaper, but if in the future you want to automate your FB better to go with Bruce controller, any mistake can cause major damage.

There is a saying here in my country .. The Cheap can be expensive.

Hotz wrote:The Cheap can be expensive.

I think we can all agree on that one, especially if you've seen or used some Chinese auto parts

Jim