My Power Controller

[Capt-Cudellez]

Also, I don't think that ebay link is quite the right controller. Note that although it claims single phase it also says 24-380v. Not possible from 240v single phase with this type of controller..

Jolly john's relay is fine, just because we get 240v as domestic supply doesn't mean this voltage can't be stepped up or down for industrial applications. It can switch a voltage anywhere in that range as long as its not exceeding the 25a limit.

[ant]

You can't step 240v up with a phase angle controller. You can only clip it down. It may well work in some way with 240v but one that is intended to go from 0-240v full range on the pot seems more appropriate.At least in my opinion.

That one is likely intended for loads that use two hots from three phase to power them. They are still often referred to as single phase although you would think they would be called two phase.

[Capt-Cudellez]

I wasn't saying the controller could step it up, I was meaning the voltage going into the controller could be higher or lower than 240v and it still works.

[ant]

Yes you may well be right. Each to their own. I'll use one intended for 240v if I use one. I am going to try an induction heater first.

The Russians seem to have done well with them for a few years now. My keg is magnetic but not as strongly as mild steel so I don't know if it will be efficient enough or take forever to heat up. Hard to tell from google translate exactly what the Russians use as boilers but some of them used with induction seem to be the right size so fingers crossed.

[Anavrin]

I've just had a look at these SSR's and there data sheet, the 25amp one will do fine, even a 3kw element only takes half that current at 240v

[ant]

380v, 240v or both?

[ant]

Thinking it through, if the 380v does run off two hots the 24v might just be as low as the two phases ever get as when one is at zero the other could be at 24v. So on true single phase it would still achieve zero not 24v.

In which case the higher voltage rating is a bonus not a hinderance. It was just the phases confusing me.

[Anavrin]

The 24v-380v is simply the working range, it only works on one phase and is to connected inline with the live phase.

Just a note on these type of SSR's they work by clipping the ac waveform, the output voltage will remain at 240v until the they pass half way, then they start to reduce the voltage.

As they are controlled by a variable resistor, if you could find the point and the resistance value of half way, you could add a fixed resistor in series with a lower value variable one, this way you could still half the power to your element without reducing the voltage.

If your only going to use it on your pot with a single element you can just ignore the above but if you use it on anything else that's more critical about the voltage requirements, my way ensures the mains supply voltage is always at 240v for example you could half the power to an airstill without effecting the fan speed.

[ant]

Oh. I understood it to specify the output not the input. Hence the 0-240v. There is no 380v true single phase anywhere in the world that I am aware of. It is the voltage you get between any two phases in three phase. Some devices, such as some motors, connect between phases instead of from phase to ground. It is still one line so called single phase instead of two phase.The average voltage never reaches zero. That is the idea behind multiphase; more power more of the time. Clever bloke Tesla.

The phase angle controllers do actually change the voltage output as Brian has noted with his voltmeter set up. The voltmeter is how he dials in the power.

I read this description of why the (average) voltage changes from the get go.

"Phase Angle control uses a low frequency switch to chop an AC sine wave. The firing angle of the switch is varied. The average voltage is proportional to the area under the sine wave. Thus, the average voltage is the integral from the firing angle to the zero crossing, the cosine of the firing angle."

With this nice anigif.



If you want full 240v at reduced power then a burst fire controller would be the way to go but they are difficult to monitor with any kind of meter.They are kinda like pulse width modulation for AC.

[packapoo]

I read threads such as this with interest, pondering if I could do better with my power control and look at what you guys pick up easily on e-bay/amazon.

BFC was what I was advised to go for years ago when I first got to putting mine together.
The Mike's at Amphora steered me the whole way thru.

BFC's seem to have slipped off the radar, but maybe they weren't too bad?

[Anavrin]

@Ant

Your almost there, the area under the sine wave represents the time during the half cycle that the power is available to the load, if you look at your sine wave in your picture, the hight of it represents the voltage, what you do by clipping the wave reduces the average power, but as you can see from the animation, after half way the hight drops, this is the point when the voltage start to drop.

So if you only ever clip upto half of the sine wave, the peak voltage will not drop.

Burst fire does indeed always stay at mains voltage, it simply cuts hole sine waves out, so for a 20% reduction in power it would cut 1 out of every 5 sine waves, it's probably more suitable than phase angle controller if your only ever going to use it on a resistive load like a heating element but due to the fact it chops chunks out of the AC sine wave it makes the measuring a little difficult.

[Anavrin]

This is the one I use

http://www.united-automation.com/avr-25 ... scia-dial/

[Almanac]

Wow! That thing costs four times what mine cost to build, including the sockets and switches

Given your obvious technical prowess (Anavrin and Ant) I'm beginning to wonder if my little homebuilt power controller is even adequate or safe

AM

[Anavrin]

Lol I used to have money, when I lived alone with a small mortgage, a 16ft long heavy duty workshop shed full of brewing gear and no kids! How times have changed...

Now have a huge mortgage, a house full of kids and no money anymore!!!

To top it off, my brew shed was too big to move, and the guy who bought my old house has chopped half of it up, painted it some gay colour and turned it into a summer house :-(

[Fil]

fyi here is my ssr based power controller all bits sourced from ebay for about £20-25 circa £12 for the ssr the heatsink pot controller and sticky back 0-100 dial face in a kit from a seller no longer selling so a link would be useless.

a bright led volt/amp meter indicates an amperage drop when the knob is turned down.

my ear tells me i can maintain a simmer in the t500 boiler with just over 2amps and at 100% the element draws 8.5amps

by cutting small copper tabs and securing them under the ssr/heatsink retaining screw heads and cutting slots in the corner screw columns in the box securing the ssr externally negates the need for an internal fan, the heatsink does not get far above body temp and maintains a warm to the touch temp.

the box was a 3phase isolation switch i just unscrewed and removed the isolator switch, and the sticky back dial covers the central switch hole.