itsmoked
Electrical
- Feb 18, 2005
- 19,114
I've got a 75HP rotary phase converter at a site.
It's to run a shop full of machine tools. One's got a 25HP spindle and a CNC lathe has a 30HP chuck.
The RPC is fed with 400A 240V single phase service.
The problem is that ALL the machine tools require 220V not 240V and unfortunately what's typically delivered is 245V. This puts all the machines out of their warranty operating constraints and causes them to spew insane process stopping alarms in occasional fits. Before things went crazy at this shop a smaller RPC had the same problem and I put a 2kVA buck transformer in front of the RPC which dropped the voltage down to something like 224V which was fine.
Now with this much, MUCH larger unit I don't think I'm even going to find a buck transformer large enough to put in front of the RPC. I want to instead follow the RPC with an open delta pair of two 5kVA bucks. They only weigh 110 lbs each. HA!
Besides the little problem of having to have absolutely no load on the RPC on startup and that means not even a 40W work light (or smoke pours forth from either the idler motor or the wall mounted Box), does anyone see any problem with this after-the-RFC-method?
Keith Cress
kcress -

It's to run a shop full of machine tools. One's got a 25HP spindle and a CNC lathe has a 30HP chuck.
The RPC is fed with 400A 240V single phase service.
The problem is that ALL the machine tools require 220V not 240V and unfortunately what's typically delivered is 245V. This puts all the machines out of their warranty operating constraints and causes them to spew insane process stopping alarms in occasional fits. Before things went crazy at this shop a smaller RPC had the same problem and I put a 2kVA buck transformer in front of the RPC which dropped the voltage down to something like 224V which was fine.
Now with this much, MUCH larger unit I don't think I'm even going to find a buck transformer large enough to put in front of the RPC. I want to instead follow the RPC with an open delta pair of two 5kVA bucks. They only weigh 110 lbs each. HA!
Besides the little problem of having to have absolutely no load on the RPC on startup and that means not even a 40W work light (or smoke pours forth from either the idler motor or the wall mounted Box), does anyone see any problem with this after-the-RFC-method?
Keith Cress
kcress -