A 9kVA transformer? Tell us about it please?I use both, two VFDs on the lathe (spindle motor - and there's a long story - and suds), rotary for mill ,(with two motors and suds plus electromagnetic clutch and brake), bandsaw, Big Drill and TIG - so far. My name is Dave and I'm a machinoholic. The beauty of a rotary is it's plug and play, of a VFD is it'll do Other Things like variable speed over and under the normal range, motor soft-start, electronic braking etc. The rotary has a 9kva transformer on the mains side to give me 415v, so copes with industrial kit pretty well without digging out star points etc....
Dave H. (the other one)
An old Oxford oil-cooled arc welder*, I stripped the welding winding, 3D printed a new coil former and wound on a wallet-worth of 3.2mm (approx 8 sq mm) enamelled copper wire - the turns/volt I measured by winding 5 turns of insulated wire through the transformer core, measuring with a meter in AC, turned out to be near-as-dammit root-3 v/turn, so wound 240 turns on the new former plus 3 and 6 turn "adjustment" windings, then potted it in epoxy (in a polythene bag pumped down with a low-vacuum pump). Didn't need the adjustmentsA 9kVA transformer? Tell us about it please?
Cheers that could be really useful thanks!!The M300 is pretty easy to convert to VFD, numerous ways to do it here's mine...View attachment 315625
Hmm, would a big 240/110 transformer work? Probably limited by the secondary windings capacity...An old Oxford oil-cooled arc welder*, I stripped the welding winding, 3D printed a new coil former and wound on a wallet-worth of 3.2mm (approx 8 sq mm) enamelled copper wire - the turns/volt I measured by winding 5 turns of insulated wire through the transformer core, measuring with a meter in AC, turned out to be near-as-dammit root-3 v/turn, so wound 240 turns on the new former plus 3 and 6 turn "adjustment" windings, then potted it in epoxy (in a polythene bag pumped down with a low-vacuum pump). Didn't need the adjustments
The winding/counting the coil was the hard bit, I bought a really cheap turns counter from a nice Chinese gent on EvilBay, mounted the former on my 6" rotary table and drove it with an electric drill.
Kept the copper wire straight by coming off the reel through bearings (with washers above and below) in a "W" to straighten and tension (just move 'em closer until it's right!).
It's worked fine for a couple of years so far! It's hung off a 45a type-D breaker (post-rcd) via 63a lockable isolator and Commando socket, has never tripped (except once when Serious Noah-Style rained upon, now in a hutch!) and shows fairly low idle current according to the RPC controller's AC input meter.
Dave H. (the other one)
* Bought from EvilBay For 20 Local Currency Units thinking it had 240 and 415 tappings, but no, just 240... But now I have an isolating, not auto- transformer! Yes, the winding wire was three times that, but compare the price of a 9kva 240-415 isolating transformer....
Pass... I've heard of people using the 110v side to boost 240 mains to 350, which could be close enough, or using a pair of 240-110 with both sides in series (the two 110 windings in series on the 240 supply, the two 240v in series for 480v out, it should give a bit more, maybe 520v? Might be a bit tooo much for the rest of the RPC!Hmm, would a big 240/110 transformer work? Probably limited by the secondary windings capacity...