Energy consumption

[Mid Wales welder]

I am trying to convince my boss to get a new tig inverter as our set is really old and basic. Was just wondering if any on here knows what the electricity savings would be, I know this is a very open question with lots of variables but any opinions would be very much appreciated!

 

[chevy2]

As a guide a transformer type Cebora tig i once owned would pop a 13amp fuse on ac if welding at 130amps for more than about 30 seconds,
A typical inverter can be ran at 160amps continuous without popping the same 13amp fuse.

at a guess around a 30-40% saving on electric consumption?

 

[brightspark]

look on the data plate and look at the current input draw for each welder and its output

 

[pedrobedro]

Also a transformer is using it's power all the time it is switched on and an inverter only uses full power when it is welding and standby power when idle.

 

[chevy2]

Also a transformer is using it's power all the time it is switched on and an inverter only uses full power when it is welding and standby power when idle.

And try to choose a machine with 'fan on demand' so the fan only runs when needed,
much more user friendly also.

 

[piman]

Hello Pedrobedro,

"standby power when idle"

That is also true of a transformer, the primary current is dependant on the secondary current, i.e. the load. I'm not saying they are as efficient just that if the machine is idle there's only the magnetising current drawn by the transformer.

Alec

 

[awemawson]

A typical Oxford type oil immersed transformer welder is 85% plus efficient. However the start up surge when switched on and it initially magnetises the core can be huge - instantaneously perhaps 50 times the normal draw. It's usually this surge that pops fuses rather than the welding current. When not welding, but switched on the draw is minimal, just making up for the hysteresis losses in the core as the magnetic flux reverses each cycle.

Sorry if this doesn't back up your argument for a new welder

 

[matt1978]

We have run some simerla tests on our new range of MicorMigs and tested against some 400 amp Transformer units, it was in Idle mode where they offered the most significant savings. Because the older style transformer units we tested the fan and the water cooler was constantly running, every second it was plugged in regardless of if you actually welded or not. We based our test with welding at around 280 amps with idle time of 4.5 hours and a welding time of around 3.5 hours for each shift (this is fair given tacking, set up, pre and post weld operations, tea and smoking breaks etc) the exact figures escape me but I think ours would of used around 25 KWH in 8 hours and the "average" of the Transformer units was around 48 KWH.

 

[chevy2]

We have run some simerla tests on our new range of MicorMigs and tested against some 400 amp Transformer units, it was in Idle mode where they offered the most significant savings. Because the older style transformer units we tested the fan and the water cooler was constantly running, every second it was plugged in regardless of if you actually welded or not. We based our test with welding at around 280 amps with idle time of 4.5 hours and a welding time of around 3.5 hours for each shift (this is fair given tacking, set up, pre and post weld operations, tea and smoking breaks etc) the exact figures escape me but I think ours would of used around 25 KWH in 8 hours and the "average" of the Transformer units was around 48 KWH.

So my guess of a 30-40% saving wasn't way off when the actual figure is higher at around 45%,
not a big deal for hobbyists on occasional use but in a production envoironment a modern machine will soon pay for itself with the energy saved and possibly production levels raised with the newer technology.

 

[brightspark]

A typical Oxford type oil immersed transformer welder is 85% plus efficient. However the start up surge when switched on and it initially magnetises the core can be huge - instantaneously perhaps 50 times the normal draw. It's usually this surge that pops fuses rather than the welding current. When not welding, but switched on the draw is minimal, just making up for the hysteresis losses in the core as the magnetic flux reverses each cycle.

Sorry if this doesn't back up your argument for a new welder

a 180 amp oilcooled draws 23 amp inrush current on start up. left switched on and not in use it draws 1. 3 amp

 

[awemawson]

Theoretically the in rush current is infinite at the instant it's powered up In reality it's limited by the other circuit elements. Your 23 amps is probably the average in the first 10 mS or so I expect.

 

[PTvor]

a 180 amp oilcooled draws 23 amp inrush current on start up. left switched on and not in use it draws 1. 3 amp

That's interesting. If the oil cooled is sat there switched on but doing no welding it dissipates 240 x 1.3 = 312W, so it will get through 1kWH in just over three hours. Say a unit (1kWH) costs 15p, then it costs just under 5p an hour to idle. Not worth thinking about switching it on and off if you are doing a job, but leave it switched on overnight (12 hours) and it will cost something like 60p.

An inverter typically uses 30 to 50W when idling, probably less if it has an on demand fan, so the idle time cost more like 0.5p an hour, or 6p to leave it on overnight.

So no need at all to switch the oil cooled on and off in the course of a job to save juice and most people wouldn't leave one turned on and unattended (such as overnight) anyway.

Most cheap inverters are 85% efficient but the dearer ones are over 90% efficient, but that's only when welding.

So using the idling figures supplied by brightspark for a transformer machine, assuming 8 hour days and the welder is welding for 2 hours and idling for 6 hours, then the daily electricity savings are (6 hours x 5p) - (6 hours x 0.5p) = about 25p. That's assuming that the costs when welding are about the same, but I don't see them being wildly different. Electricity savings say, £70 a year?

Cost of an industrial grade 200A DC TIG machine? About a grand? If the boss has got any sense, he won't accept an argument to get a new TIG inverter based solely on electricity savings.

 

[chevy2]

The energy used whilst idling is hardly worth measuring for a saving,
its the difference of the maybe 15amps compared to say 28amps whilst welding that'll make the big difference on energy savings,
Although i didn't measure the actual difference i did certainly see a noticeable reduction in my electric bills when i changed over several years ago from a transformer to an inverter machine.

 

[brightspark]

i left the welder on for 4 weeks without realising it was on and a couple of 110 trannys . never gave it a thought about current use il make sure there off from now on

 

[wheresmejumper]

I would throw the whole carbon footprint thing into the argument for a better inverter from the boss, on top of the running costs and people starving in africa.

The oil cooled is good for warming your hands in a cold garage though.swings and roundabouts.

 

[PTvor]

The energy used whilst idling is hardly worth measuring for a saving,
its the difference of the maybe 15amps compared to say 28amps whilst welding that'll make the big difference on energy savings,
Although i didn't measure the actual difference i did certainly see a noticeable reduction in my electric bills when i changed over several years ago from a transformer to an inverter machine.

I think it depends what it is.

If it's a bloody great 400A industrial transformer unit with water cooling and huge fans vs an inverter based 400A unit with the cooling on demand then I can see Matt's figures would hold good. What did he say, a 25kWH saving in a working day, which assuming industrial rates for a unit are 10p is £2.50 a day and about £625 a year assuming 50 five day weeks. That's at least a serious supportive argument for going for the modern kit.

If the transformer unit he's using is more like an Oxford 180 in its idling costs, vs an industrial grade inverter DC TIG, then I don't see that the argument on electricity savings is quite so clear with savings on the same basis (10p a unit) at under £50 a year.

 

[Mid Wales welder]

Thanks to all for your replies, very informative, I knew some clever people would be along! This defiantly gives me a more convincing argument for new kit. Sorry I have taken a while to reply, new baby at home which has kept me on my toes lol.

 

[PTvor]

We still don't know what you are doing, lots of light TIG work or seriously heavy duty stuff, which seems to make difference in electricity costs. Anyway, if you are going to field a business argument, you need facts and figures and all we have so far is estimates of one sort or another.

I wouldn't base your arguments solely on electricity cost savings anyway, much less talk about carbon footprints, which were all the rage about 8 years ago, but have dropped below the radar in recent years. Some of my bosses would have loved the idea that their activities lead to someone starving, so I'd skip that line too.

You want to keep up and be working on the latest gear - this place could fold and you don't want to be talking about how you've been working with 25 year old stuff commonly regarded as junk. He wants profitability, making the most from the least. Part of the problem with British industry was that it wasn't prepared to move with the times and persisted with what became museum pieces until it collapsed.

There are a few other lines of argument for getting new kit apart from energy savings; greater productivity, wider range of work possible, exciting new opportunities, not becoming outdated so not considered for new work, lower costs, happier workforce.

 

[Mid Wales welder]

You want to keep up and be working on the latest gear - this place could fold and you don't want to be talking about how you've been working with 25 year old stuff commonly regarded as junk. He wants profitability, making the most from the least. Part of the problem with British industry was that it wasn't prepared to move with the times and persisted with what became museum pieces until it collapsed.

There are a few other lines of argument for getting new kit apart from energy savings; greater productivity, wider range of work possible, exciting new opportunities, not becoming outdated so not considered for new work, lower costs, happier workforce.

It's mainly used for lighter work, we rarely do anything that uses more than 200amps.
The electricity saving saren't the only argument for a new set, it's just a bit more ammo for the argument. As you say the greater productivity, range of work and especially not becoming outdated are all part of it.