Extra capacitors - A good thing?

[wombar]

Hi All,

I've done a massive amount of reading over the last couple weeks and I've got my choice down to three units (in order of preference). Was hoping for a little advice.

Britarc 241 - Very local to me, available immediately (plus it's blue which I like )
Portamig 235 - Excellent machine backed by excellent service
Oxford 240-1

The Oxford and Britarc both have smoothing capactitors fitted, which ups the price by about £50. I've read the threads that talk about these, but my question is this.

Does having these extra caps mean there's more to go wrong? I'm hoping whatever I buy is going to be like the old "British Built" appliances that are still going strong 20 years later.

I'm just wondering whether having the extra caps is asking for trouble a few years down the line.

Any opinions/facts/guesses would be greatly appreciated.

 

[shenion]

The caps are worked hard, especially on single-phase machines. They loose capacity over time. They can be rated from 1000 to 3000 hours of use. In welding applications, they probably will not last their full life. It is not that they will just fail but after a lot of use they will not be very effective (the rated hours is where they reach 50% of thir capacity.) So, you will lose some output power.

There are threads here where people have had to replace them. Usually that is on 15 or more year old machines.

I would expect a production machine used every day to need new caps every 2-3 years. There the cost would be not an issue.

I added caps to my Miller. It smoothed the arc but increases the wire speed sensitivity. If wire speed gets a bit slow, the voltage goes up and the wire burns back. I really only see this on welding below 30 amps on 0.6mm wire.

I'd really not worry either way as the machines are designed with or without the caps (different voltage range.) They should last for years.

weldequip says the PortaMIGs are custom made. I bet he could have them add the caps. I bet that is why the Oxford does not go down as low amps due to increased output with caps.

The only reliability issue is it adds more connections that may work loose. No big deal to check them every few years.

 

[wombar]

Thanks for the reply shenion It's great to get some info from someone who's had some hands on experience with these kinds of things. I've also done a bit of digging/research this morning.

Turns out that TecArc are like email ninjas I emailed them asking them some simple questions about the caps and they replied within minutes. Here's the outcome:

- They will be able to supply the caps to me when replacements are needed (which they'll guarantee being able to supply for at least 15 years).

- The guy reckoned they should last at least 15 years dependant on use, probably more (I said it would be hobby use so he had a benchmark).

So, it really doesn't sound like having the caps is going to cause any premature problems. Trouble is, that means I've got a decision to make over the weekend now. Might get to the point where I toss a coin between the Britarc and Portamig

 

[wombar]

Just another quick update. I figured it's probably worth people knowing what it might cost to repair these caps in the future. Obviously prices will rise etc, but this is correct for today at least

I was quoted £29 each for the caps from TecArc (there are 2 in the Britarc 241/Oxford 240), and I suspect there's probably a delivery charge on there as well. It's probably something most of us could tackle ourselves, but if you need to hire someone, it really shouldn't take long or cost much. I'd guess that you'll probably be looking around the £100 mark all in if you're doing this outside of a warranty period. Doing that once every 15+ years really doesn't worry me.

Squinting at pics on here I think (but don't rely on my eyes) they're 22000uF 50Vdc. You can probably source them cheaper and save yourself ~£30, but I'd just buy the originals if it was me.

So (for me at least), the caps certainly aren't a cause for concern. You learn something new every day

 

[wellyweld]

Wombar,
I hope the coin is lucky for me! Remember local is good.