Hey, for my bachelor thesis i am developing a control system for medical autoclaves. glorified pressure cookers.

the control unit runs off of 24v DC where as the actuators, (valves and pumps) run off of 24v AC!

currently i am using a transformer to get the 24v AC and a AC to DC converter for the 24v DC.

what i would love is both of those in one, meaning one AC input and two channel outputs providing AC and DC. has anyone ever seen something like this? all i find on google are loads of converters,

thanks a bunch!
- Sonzai

 

Since you already require AC, which the transformer supplies, I don't see the object of making a supply with an AC output.
What would that gain you?

 

I would second that apart from the fact that I suspect what you actually mean is that you want a power supply module so that it is all neat and well defined.

Firstly I would respectfully suggest that you actually do not want your actuators fed from the same supply as your control circuit at least not without adiquate protection...

If you get a fault it will most likely be a pump or valve and if that occured you wouldnt want the control system browning out.
Of course if thew AC supply can easily handle your maximum fault current, whilst the protection trips, which is way above the actual rating of a fuse or breaker, then you are golden but that would require a very big, comparitivly speaking, supply.

My aproach when working with critical stuff is to seperaqte control and drive voltages and for that reason I would actually recomend two seperate supplies or at the very least a battery backed DC supply if the SAC must be common.

Once designed the entire PSU module, multiple rails and primary protection, would get its own enclosure with some form of keyed connector ideally.

You might even considder a power module that incopperastes the output switching, if there are only a few items to deal with, that way everything would plug into the supply, including control signals from your PLC/logic circuit, that would command the PSU to switch particular outputs...

Just musing.... Have you looked at the SIL requirement?
I would imagine that hot stuff in a big box at high pressure is going to require some careful thought RE interlocking and fail safe measures and all that will almost cirtainly impact your PSU requirements.

Al

 

Put your transformer and converter in a box and label the input and outputs.
Now you have both of those in one

 

thanks for all the replies, some more info about everything,

they used to have an old PLC Mitsubishi system, i replaced it with a Beckhoff system. it is a wastewater autoclave using super heated water.

previously they used a transformer to supply the 24v AC to the actuators and used a converter for the control system. basically two separate power sources.

what i wanted, to save space, was taking the input from the mains, feed it into a power supply unit, that has a transformer and a converter built in. so that i could provide the ac and dc supply voltages with one module. the safety requirements are met for the system and if something breaks, there are measures in place to prevent further harm to other components. i could just slap both into a nice box, but id like to mount it all on the DIN-rails and keep it nice and small

attached are photos of the previous and new system. first image (3650) has the 24v dc at the top right and 24v ac transformer on the bottom left. second image (4610) has the new control system and the 24v ac on a table infront of the box and the 24v dc to the left of the control system.

 

I dont think you will get the footprint down by feeding low voltage AC into a PSU to get low volltage DC if only because the currents on the input will be higher and the voltage will be lower which would need a bugger bridge and much bigger caps so the supply its self will be larger.

You are also loosing a layer of safety because your beckhoff will be exposed to more voltage fluctuation that it would with the origionmal configuration.

Honestly I would go with what you have, all be it in a single enclosure as opposed to the table based solution just kidding.

Al

 

I dont think you will get the footprint down by feeding low voltage AC into a PSU to get low volltage DC if only because the currents on the input will be higher and the voltage will be lower which would need a bugger bridge and much bigger caps so the supply its self will be larger.

You are also loosing a layer of safety because your beckhoff will be exposed to more voltage fluctuation that it would with the origionmal configuration.

Honestly I would go with what you have, all be it in a single enclosure as opposed to the table based solution just kidding.

Al

yeah i guess ill just stick to what i have! sucks i cant cut down on some more space