Sunday, February 26, 2012

tooling update, part the first

Rotary phase converter ordered. This is a big fucking deal, because it means I now have a power source for the Bridgeport (knee mill, for you philistines) that will last as long as the mill does. It is slightly larger, much heavier, and slightly less convenient and slick as the variable-frequency solid state AC motor drive which it replaces. However, the rotary phase converter will not, ever, under any circumstances, forget its programming. It cannot have its firmware mind bricked, because it hasn't got one.


I should have listened to the old timers. I'm stubborn, and I still think like a young turk. But I do learn, eventually.

When this thing arrives, a whole bunch of work which has been lying around waiting for the mill will start getting done. I decided to order a complete, ready-to-install system with commercial idler (a motor without a shaft) for various reasons, not least of which is the fact that the two "reputable" American manufacturers of kits (wherein you provide only the motor which, one presumes, you can purchase locally for less) -- did not return my inquiries for price and availability. So fuck 'em.

For COTS units, the scuttlebutt on the various web forums for machinists was that it was mostly down to American Rotary and TemCo. I chose the latter because their warranty looked a tad better. Both companies have good reputations.

I had set up a search on eBay, priced to find a used unit of one of the two above brands, when along came a bunch of hits on new units. As far as I can tell, both companies are selling direct on eBay, and both are having a roughly 40% off price war. With, I might add, free shipping, which is kinda important for an object weighing 94 pounds.

Incidentally, me being not only a belt-n-suspenders sort but also a burnt-child-fears-the-flame sort, I'm going to look into protecting the few components in this unit which could -- at least in theory -- be damaged by a sufficiently large surge. All rotary converters (AFAIK) contain both relays and large motor-run-rated paper-and-oil type capacitors. The capacitors have a really long life - much better than elecrolytics, but they or the relay windings could in theory be zorched by a big surge.

Industrial-strength MOVs are not expensive, and I already have one, I think. Gotta double-check its voltage rating. Oh relax, fuses are already involved in the machine disconnect, so the MOVs, the surge protection devices I love to hate, will not present a significant hazard when they fail. They'll also be inside a metal box.

1 comment:

jdmorse said...

Well, good! Of course, I can't comment on which system is best since I have three phase wired in.