Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Automatic transfer switch help me!!!

Status
Not open for further replies.

Pretto

New Member
does anybody know where I can find any schematic about an Automatic transfer switch? or some information that can help me? because I am trying at a long time to build one, but I don't have any idea, I would like to do something using a pic microcontroller.

it would be something as in the diagram below..

Regards
Elson
 

Attachments

  • static transfer switch.gif
    static transfer switch.gif
    4.5 KB · Views: 2,197
Pretto said:
does anybody know where I can find any schematic about an Automatic transfer switch? or some information that can help me? because I am trying at a long time to build one, but I don't have any idea, I would like to do something using a pic microcontroller.

it would be something as in the diagram below..

Regards
Elson

You need to specify the speed of the switch and current capability. Most industrial level transfer switches can do it within a 1/4 of a cycle during an interruption. The speed factor will greatly affect the complexity of the switches etc. When interrupting a large current, huge spikes can be generated which wreak havoc on logic and the SCRs or other switching devices.
 
I don't have any info on the circuit of the transfer switch but I'm sure it will be very complex.

I did tested many and they all have several circuit boards the size of A4 paper connected together with ribbon cables. So I believe the schematic diagram would be running into many pages long.

This is how I tested them. I connected an UV oscillograph(an recorder that draw traces using UV light on UV sensitive paper roll) to the transfer switch output, started it running and then I switch off the normal source so the switch transfer to the alternative source. Waited a bit and switch the normal source back on and watch the transfer switch did the transfer yet again.

There should not be any discontinuity in the output sine waveform, like nothing had happened, not even a spike. Otherwise, why use such a switch when a simple relay will do the job. The transfer switch was part of an inverter rated at 110V and 200A full load.
 
Last edited:
Okay, so we're talking serious current here. I've seen UPS systems like you've mentioned, but they operate slightly differently. They take AC mains and convert to DC to charge batteries, and also take that DC and invert back to AC for the output. If the AC mains fail, then the batteries take over, and you see no interruption at all in the output, because it isn't really switching between the two, it just ceases to charge the DC batteries, but the DC voltage is still there, and the inverter works as normal. Such a schematic would be quite complicated, I'll take a look around.
 
Analog said:
If the AC mains fail, then the batteries take over, and you see no interruption at all in the output, because it isn't really switching between the two, it just ceases to charge the DC batteries, but the DC voltage is still there, and the inverter works as normal. Such a schematic would be quite complicated, I'll take a look around.

Big inverter don't work like that. The output is actually from the AC input feed while the DC side is not taking any significant current or no current at all. Otherwise the inverter loss will be too much as it will be running 24-7.

The vital part of the circuit is to startup the inverter quickly when AC fail which definitely going to take some time and how to maintain the output voltage waveform without sagging. There are a lot of tricks involved to achieve just that.
 
eblc1388 said:
Big inverter don't work like that. The output is actually from the AC input feed while the DC side is not taking any significant current or no current at all. Otherwise the inverter loss will be too much as it will be running 24-7.

The vital part of the circuit is to startup the inverter quickly when AC fail which definitely going to take some time and how to maintain the output voltage waveform without sagging. There are a lot of tricks involved to achieve just that.

I disagree. I installed a Liebert 3phase 300KVA UPS, and that's exactly how it worked.
 
Analog said:
I disagree. I installed a xxxxxxx 3phase 300KVA UPS, and that's exactly how it worked.

My comment has nothing to do with a particular brand of UPS but to online-UPS in general.

So in normal use, AC has to be rectified and then inverted back to AC again. Therefore two conversions are involved. I see that some UPS manufacturers now claim an overall UPS efficiency to be over 90% but then again with a load at 240KW, a 10% loss would be 24KW which is quite high to me if I am the one to pay for it.

I have no idea whether offline/standby UPS exists in this power range.
 
Last edited:
I've not really read up on this but here's my theory on how big UPSs work.

The inverter is continiously running but off load so it doesn't draw much current and it's also in phase with the AC supply. When the power fails the inverter just takes the load but is disconnected from the mains to stop it from trying to power everything else on the same phase. When the mains power is restored it's simply connected to the mains again. The only difficult part is detecting whether the inverter is powering the load or the mains is, but this can be achieved using a current sensing transformer/resistor.
 
there are 3 poles, 1 neutral i'd assume.

I seriously wouldnt suggest you building your own automatic switch, the relay part is easy, but the contact part is not. arc flash can go up to 30,000 degrees and it can vaperize copper bars. and when you can not keep them inphase your engine will shaft.
 
automatic transfer switch

does anybody know where I can find any schematic about an Automatic transfer switch? or some information that can help me? because I am trying at a long time to build one, but I don't have any idea, I would like to do something using a pic microcontroller.

it would be something as in the diagram below..

Regards
Elson


hi,

did u find any schematics for automatic transfer switch, can u share it with me

thanx
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top