De-rating 3 phase inverters - final result

Charles

Interesting, as I'll probably be doing something similar soon. I was hoping to run my 7hp DSG motor from a 10hp inverter in a similar way, that's not looking too good now :-( , though it does have a clutched drive.

How generous is the cabling to your transformer? My converter struggles a bit to start my K&T CVA at top speed (3k rpm,

4hp motor) but I reckon some of that may be voltage drop in the cables to & from the idler motor. It's in the plan to try some 'oversized' cable before too long. OTOH my 'new' CVA has a 4hp single phase motor, it starts fine at top speed (2200) here (supplied via the same dedicated 16 sqmm cable from the main CU as for my converter), whereas it struggled when I tried it in the Vendor's garage (on a '32A supply' & he is an electrician). I've come to the conclusion over the years that quite a small volts drop can make a big difference to starting performance.

Tim

Tim

The cabling is reasonably generous and very short. However you might be lucky. I assume that it's a 1500 rpm motor on the DSG and a 750rpm top speed. That's a *much* nicer combination. The CVA ran fine up to 1000rpm on a 5HP converter. The two higher ranges needed a further 5HP in inverter rating! Give it a whirl and see what happens.

(BTW if anyone wants cheap 5HP 415 volt inverter get in touch. It should work fine on a Student, Bridgeport or similar - the start up loading on turret mills is much lower).

Regards

Charles

It's actually 1300 top speed, though clutched drive which should help a lot so far as staring goes.

I certainly shall, I've collected all the bits now, the only missing ingredient is time..... (and energy to use the time!)

Tim

clutched

'oversized'

tried it

volts

..hehe, I've got a 11KV 3phase line crossing my new place, with a

11KV -> 415 3 phase transformer on a pair of poles on my land just waiting for a 200 amp per phase supply to be run into the new workshop, that should sort out starting issuses on big motors , though not a good place to practise fly casting, as someone at the Hog Roast said this afternoon

AWEM

No. Carbon fibre rods and 11KVA is a poor combination. So why is there is always a big-fish lie under the blasted things ;-) ttfn

Blooming heck. The "high speed" model. I thought yours was a plain bearing version?

It doesn't take long to find out whether it works. Getting it properly wired in is a PITA

Charles

EMR

have you costed it out yet ? The reason I ask is my brother has the same on his farm but they want that much to string it in he's still on generators.

I know it can vary place to place but it was obscene what he was quoted.

similar

cable

electrician).

missing

They've quoted me £1100 for a 100a supply 'off the book', but a 200a becomes a 'small project' and requires an engineer !

AWEM

Yes, & some people just don't seem to believe it/read the signs etc. Someone died when fishing half a mile from here in just that way.

Tim

We've got an 11kV pole in the garden, & a transformer 20 metres away, but I reckon it would cost a few bob to get 3-phase brought in.

Tim

Same here. Do you reckon that they'd do a deal on the £5ish per year peppercorn rent that they pay for the pole in return for 3 phase? It's only a 220 year payback.

Charles

I've still not found any wayleaves in the deeds letting it be there at all !

AWEM

If anyone is getting anything for 'our' pole it'll still be British Waterways. They were trying hard to find excuses to duck out of selling the place to us, as sitting tenants, after formally agreeing to do it, so we didn't ask any questions which weren't absolutely essential. As it was, it took 3 1/2 years between them agreeing to sell and signing on the dotted line Maybe I should ask them now. Let's see, a fiver a year for 17 years, plus interest, compounded, ought to just about pay for a solicitor to write to them ;-)

Deeds? What Deeds? AFAIR we had to just have blind faith that it was theirs to sell!!

Cheers Tim

Just get them to put in 2 100A supplies to a common meter ;) You might even get a quantity order discount ;)

Dave

When I got 3 phase, the power company policy supplied the first chain for free. :-) Paid for overhead $22.00 and they ended up supplying underground, 85 yards odd. Hit me for $60.00 :-( Last century though. :-)

Tom

Over here it most probably be regarded as part of the Queen's chain! :-)

Tom

[]

Had the hog learned that the hard way?

The concept of a Hog using a fly fishing set up boggles the mind What did amaze me was that the Hog had to roast for 9 hours - poor farmers wife crept into our place at 5 in the morning to set it up - what a way to earn a living!

AWEM