Running a hypertherm 85 from a generator, what size?

[pc18]

I am looking to run a hypertherm 85 from a generator. I've looked on their website and found this info i have attached.

I'm not sure i understand the numbers correct. Does it mean to run it at full power i need a 20kva 3 phase generator or would i need one slightly bigger?

I have previously used a hypertherm 105 powered by i think a 35kva generator and that seemed to handle it no bother at all.
I just want to make sure i buy a generator which will run the ht85 without issue.

I have a David Brown 996 tractor so i am considering a pto powered generator as they seem to come up cheaper. But i am considering an engine driven unit also.

 

[Memmeddu]

The bigger the better

 

[GRW]

I recall the DB996, but no idea how much HP one has. I'd guess though maybe 50HP??
If so that's 40kW (mechanical). You'd run a PTO Gen of perhaps 30KVA pretty much at full output with 50HP.

Small 3ph PTO Gens  can be found pretty cheaply now, as they are nowhere near big enough for the modern huge Dairy operations, so the market for them is limited.
Something like an N J Froment Magnate PTO Gen in decent nick (& others) can be a good buy - even very old ones tend to be reliable if stored well.
That said - if the Plasma will be in regular use, I'd never suggest a PTO Gen. They might be capable of doing it, but they are a PITA to set up all the time, and you'll use more fuel than in an engine set doing it (plus the added dangers of PTO shafts and the racket from the tractor & driveline, and the amount of space needed).

The data sheet states 20kw for full output from the PC (a 30kva genset is 24kw).

G.

 

[pc18]

I recall the DB996, but no idea how much HP one has. I'd guess though maybe 50HP??
If so that's 40kW (mechanical). You'd run a PTO Gen of perhaps 30KVA pretty much at full output with 50HP.

Small 3ph PTO Gens  can be found pretty cheaply now, as they are nowhere near big enough for the modern huge Dairy operations, so the market for them is limited.
Something like an N J Froment Magnate PTO Gen in decent nick (& others) can be a good buy - even very old ones tend to be reliable if stored well.
That said - if the Plasma will be in regular use, I'd never suggest a PTO Gen. They might be capable of doing it, but they are a PITA to set up all the time, and you'll use more fuel than in an engine set doing it (plus the added dangers of PTO shafts and the racket from the tractor & driveline, and the amount of space needed).

The data sheet states 20kw for full output from the PC (a 30kva genset is 24kw).

G.

Thanks for the reply G. The 996 is about 62hp i think, it runs really well for an old girl and uses very little red diesel. Those are the type of pto generator ive seen pop up on facebook which i think i am going to give them a go. Is there much to go wrong on them? I was hoping to also add a single phase 240v output from one too which i believe can be done if it didnt already have one. The plasma wouldnt be in regular use, just now and again. I have a Fobco 10 eight pillar drill which is 3 phase. i might end up with other odd bits of 3 phase gear in the future but they would only get used now and again, so the generator can just sit there behind the tractor for when i need it. space isnt an issue and it would be parked up under a lean to next to my garage outside. It should also give the David Brown a decent bit of work hopefully.

 

[GRW]

Thanks for the reply G. The 996 is about 62hp i think, it runs really well for an old girl and uses very little red diesel. Those are the type of pto generator ive seen pop up on facebook which i think i am going to give them a go. Is there much to go wrong on them? I was hoping to also add a single phase 240v output from one too which i believe can be done if it didnt already have one. The plasma wouldnt be in regular use, just now and again. I have a Fobco 10 eight pillar drill which is 3 phase. i might end up with other odd bits of 3 phase gear in the future but they would only get used now and again, so the generator can just sit there behind the tractor for when i need it. space isnt an issue and it would be parked up under a lean to next to my garage outside. It should also give the David Brown a decent bit of work hopefully.

The old Froments are really solid 4-pole, old school things, using an old design BKB alternator.
Checking the brushes, commutator, slip rings, brush holders & springs is a good idea (slide the rear cylindrical cover off) and there are old-school coil wound potentiometers that can get brittle and fracture - but usually they are OK.
Insulation varnishing on the old tanks is usually extremely good (better than modern stuff) so overall they are robust.

Selenium Bridge rectifiers can fail with age and aren't available any more.... but I know one of the electrical guys I worked with used to replace it with a silicon unit, and add resistors to get the output back to match the old Selenium unit - so overall they are good kit.
Always check the pto reduction gearbox for play, but usually they are OK, I think these used a HP grease like a 140 instead of the EP80/90 used in the BIMA boxes fitted to Meccalte alternator PTO sets (a lot of those about too, built by Gloster Gens and A&M Gens).

Although the odd one has been thrashed running a grain drier, most PTO sets are standby & haven't done much work. Biggest issues are age and kept/installed somewhere very damp, and odd ones got cooked by the farmer expanding his parlour once or twice over the decades, but not upgrading the generator (& a big modern tractor with enough HP can force a PTO Gen to give a hell of a lot more power than it was designed to give).

Still plenty about though, so finding a tidy one should be possible. Don't overpay though, as although they were expensive machines new, today they are not really any more new than they were 25 years ago - and small sets aren't of any use to a big modern industrial farm.

Adding a 1ph supply across one phase & neutral is fine.... but limit yourself to small power like hand power tools (you don't want to hammer one phase when there's no load on the others - the phase imbalance can cause damage)

Cheers, G.

 

[pc18]

The old Froments are really solid 4-pole, old school things, using an old design BKB alternator.
Checking the brushes, commutator, slip rings, brush holders & springs is a good idea (slide the rear cylindrical cover off) and there are old-school coil wound potentiometers that can get brittle and fracture - but usually they are OK.
Insulation varnishing on the old tanks is usually extremely good (better than modern stuff) so overall they are robust.

Selenium Bridge rectifiers can fail with age and aren't available any more.... but I know one of the electrical guys I worked with used to replace it with a silicon unit, and add resistors to get the output back to match the old Selenium unit - so overall they are good kit.
Always check the pto reduction gearbox for play, but usually they are OK, I think these used a HP grease like a 140 instead of the EP80/90 used in the BIMA boxes fitted to Meccalte alternator PTO sets (a lot of those about too, built by Gloster Gens and A&M Gens).

Although the odd one has been thrashed running a grain drier, most PTO sets are standby & haven't done much work. Biggest issues are age and kept/installed somewhere very damp, and odd ones got cooked by the farmer expanding his parlour once or twice over the decades, but not upgrading the generator (& a big modern tractor with enough HP can force a PTO Gen to give a hell of a lot more power than it was designed to give).

Still plenty about though, so finding a tidy one should be possible. Don't overpay though, as although they were expensive machines new, today they are not really any more new than they were 25 years ago - and small sets aren't of any use to a big modern industrial farm.

Adding a 1ph supply across one phase & neutral is fine.... but limit yourself to small power like hand power tools (you don't want to hammer one phase when there's no load on the others - the phase imbalance can cause damage)

Cheers, G.

Thanks for all the info! That post is a great help. It sounds like these older units are pretty solid option for what i need then. The odd ones seem to come up so hopefully i can pick one up locally. I might even ask some of the local farmers if they have one sitting about.
Thanks again!