Powcon the legend

[Matthew Gunter]

So, having got the 300 back up and running, the boss said to one of the guys ‘whip up a trolley to put it on’

Behold, the tower of powcon...

 

[RCP]

Thanks to this old thread, I was able to repair my old Powcon 300SM. Matthew Gunter's picture of his failed capacitors is exactly the same failure mine had. I replaced the three 0.6 microfarad Rifa capacitors and was about to replace the 0.068 microfarad capacitor in the lower left of his picture, but my original one(which on mine is also a Rifa) has a 1000V rating written on it and I could only find a 250VAC replacement in the same size. The original wasn't bulged or cracked and with the different voltage rating I was hesitant to replace that one. Now that I'm looking at that photo again, perhaps if I went to a larger(physical size) capacitor I could find a replacement with a higher voltage rating. It looks like in Matthew Gunter's picture that one of the legs on his TRW 0.068 microfarad capacitor is actually installed in a different hole than what mine is so a longer in size capacitor should work for mine too.

If I had to guess this assembly is considered a full wave bridge rectifier? Anyway, thanks for the information and the picture provided in this thead; my welder works again.

 

[eddie49]

Hello, and welcome to the Forum !
Yes, that board is a full-wave bridge rectifier for a 3-phase supply, with 6 diodes CR1 to CR6. Inverters, even today, always start off by rectifying the AC mains input, then smoothing it with some capacitors. The resulting DC Bus, which depending on input voltage can be anywhere from 300 to 600v DC, is then fed to the "chopper" circuit to be converted to high frequency AC. Modern inverters use MOSFET or IGBT transistors to do this, and run at a frequency of 20 to 100 KHz. At the time the Powcon was designed, power transistors could not handle such high voltages, so they used SCRs ( thyristors ). The switching frequency is much lower - about 5 KHz - which is why you can
hear them.

Those capacitors are used for filtering and spike suppression. They help to stop noise going back up the supply line. Some notes on the specifications for that type of capacitor in Post #14:
https://www.mig-welding.co.uk/forum/threads/tradesarc-131i-no-weld.97737/#post-1479974

I have recently bought a Powcon 300ST. I still have to set the jumpers for operation on single phase.

 

[RCP]

Hello, and welcome to the Forum !
Yes, that board is a full-wave bridge rectifier for a 3-phase supply, with 6 diodes CR1 to CR6. Inverters, even today, always start off by rectifying the AC mains input, then smoothing it with some capacitors. The resulting DC Bus, which depending on input voltage can be anywhere from 300 to 600v DC, is then fed to the "chopper" circuit to be converted to high frequency AC. Modern inverters use MOSFET or IGBT transistors to do this, and run at a frequency of 20 to 100 KHz. At the time the Powcon was designed, power transistors could not handle such high voltages, so they used SCRs ( thyristors ). The switching frequency is much lower - about 5 KHz - which is why you can
hear them.

Those capacitors are used for filtering and spike suppression. They help to stop noise going back up the supply line. Some notes on the specifications for that type of capacitor in Post #14:
https://www.mig-welding.co.uk/forum/threads/tradesarc-131i-no-weld.97737/#post-1479974

I have recently bought a Powcon 300ST. I still have to set the jumpers for operation on single phase.

Thanks for the welcome and reply! I don't know a whole lot about electronics, but I learn more as I go I guess. I was surprised that I was actually able to do a decent job soldering the new capacitors in the circuit board. Perhaps I've finally figured out soldering.

My Powcon was originally set to three phase when I bought mine a few years ago too. I set it up to run on single phase and have been using it mostly for stick welding. I do have an old Hobart 2210 wire feeder that came with the welder for Mig and I also have a bottle of CO2/Argon gas for it, but haven't really dialed in the settings completely for that yet. I was trying different settings with it set up for Mig when all of that capacitor smoke came pouring out the back of it the other day!

Anyway, thanks for the electrical explanation and the welcome!

 

[carbon]

I have recently bought a Powcon 300ST. I still have to set the jumpers for operation on single phase.

I hope you like it, my 300SM has been very reliable

 

[carbon]

My Powcon was originally set to three phase when I bought mine a few years ago too. I set it up to run on single phase and have been using it mostly for stick welding.

I don’t use mine much for stick but find the noise they make a little different

 

[zeppelin builder]

Hello, and welcome to the Forum !
Yes, that board is a full-wave bridge rectifier for a 3-phase supply, with 6 diodes CR1 to CR6. Inverters, even today, always start off by rectifying the AC mains input, then smoothing it with some capacitors. The resulting DC Bus, which depending on input voltage can be anywhere from 300 to 600v DC, is then fed to the "chopper" circuit to be converted to high frequency AC. Modern inverters use MOSFET or IGBT transistors to do this, and run at a frequency of 20 to 100 KHz. At the time the Powcon was designed, power transistors could not handle such high voltages, so they used SCRs ( thyristors ). The switching frequency is much lower - about 5 KHz - which is why you can
hear them.

Those capacitors are used for filtering and spike suppression. They help to stop noise going back up the supply line. Some notes on the specifications for that type of capacitor in Post #14:
https://www.mig-welding.co.uk/forum/threads/tradesarc-131i-no-weld.97737/#post-1479974

I have recently bought a Powcon 300ST. I still have to set the jumpers for operation on single phase.

i believe you can connect to single phase domestic supply but you are limited to burning small electrodes , a lot of the yank machines like my old hobart are like this think its split phase its called here iirc
but it draws about 55 amps per phase so you need very heavy duty power supply , its a big old transformer of course

 

[carbon]

According to the manuals it drops the max current in the high range to 200amps when on single phase for the 300SM, ST and SS

 

[zeppelin builder]

According to the manuals it drops the max current in the high range to 200amps when on single phase for the 300SM, ST and SS

thats very usable then , one of mine stopped ticking ,had a quick look for obvious burnt bits but couldnt see owt! might try swapping the boards off the other one to narrow it down , great welders , whistles like an old bullet

 

[carbon]

Needs to be a big plug as not going to do that from a 13amp plug

 

[Boilermaker]

Ticking is rectifier coming on to create an open circuit voltage for arc.

Also believe that they are dual voltage and can be used on single phase with reduced output by swapping position of links inside.

The one I have 300sm is either constant voltage or constant current depending on what mode its in.

Don't use mine on arc much, usually have it either attached to a powcon power drive II or a spool gun for aluminium welding. Really like the good duty cycle that they have

 

[Boilermaker]

Carbon you say that you have a spool gun on your 300sm. What type of spool gun are you using. I have 300sm and power drive II also.

 

[carbon]

I think it is a ck systematics but not sure if its available anymore but no reason why others wouldn't fit as long as they are 115v as then it can be powered from the back panel connector like the powerdrive II

 

[shipyarddude]

I just was just recently given a 300sm with the same resistor problem. Lots of white stinky smoke rolling out of the back, lol. My questions are, where can I find the resistors? Can any share a copy of the PowCon 300sm manual with me, if anyone has it? I've check the links for the manuals listed in thread earlier, and it seems that they are no longer available. My 300 came setup to run 230 volts, if I'm understanding what I've read, with this bus bar configuration in all 3 locations it'll operate 230 volt single or three phase? Please correct me if I'm mistaken about this ! And this may be a dumb question, but can I use a 5500 watt generac generator to power this machine to weeks stuck up to 1/8 7018, or will that but provide enough power? Thank You for any help you can provide, Brian aka (shipyarddude).

 

[shipyarddude]

Sorry about the typo in the above post ! My likely bad idea and dumb question is, can I power it from a 5500 watt generator to weld up to 1/8" 7018 or will this not provide enough power ? Thanks ahead of Time, Brian

 

[carbon]

Its usually the capacitors on the input that dry out and fail.
You should be able to use 'x2' capacitors of the same value.
Ive included a pdf of the manual.
230v operation can be either single or three phase but follow the wiring instructions in the manual.
You may be able to use it from your generator but possible only in the low range but read the section in the manual about powering from a generator.

 

[Matthew Gunter]

Hi @carbon, i’m wondering if you’ll be able to help me out on this.

I’ve bought the PowCon tower from my old boss and i’m keeping the 300sm and pd2 for my own use and wondered if there is any way to fit a remote weld power control on the pd2?

looking at the pinout it seems that there is pins for the control of weld power.

Any thoughts?

Thanks

 

[carbon]

The remote power lead is plugged into socket on the back of the 300sm, so there's no reason why it cant be done. I keep meaning to do it on mine but never seem to get around to it. I think its just a 5k pot for the remote and using pins 11-14 as the diagram on page 13 of the manual and a little more detail on page 36 'J4'

 

[carbon]

I think it may need the enable pin connected so that power control is from the remote rather than the front panel. I would assume connecting pin 11 to pin 14 would 'enable' the remote as pin 10 enable is connected to pin 14 on the diagram from page 10. But Ive not tried that or even taken the plug to my pd2 apart to check.

 

[Matthew Gunter]

I think it may need the enable pin connected so that power control is from the remote rather than the front panel. I would assume connecting pin 11 to pin 14 would 'enable' the remote as pin 10 enable is connected to pin 14 on the diagram from page 10. But Ive not tried that or even taken the plug to my pd2 apart to check.

i get the machine in a couple of weeks so i’ll be going through it and giving it a good clean up before applying any power to it. I’ll also investigate the wiring a bit more once i have it with me.

You don't happen to know of a wiring diagram for the RH-100M do you by any chance?

Thanks