By No Means Am I An Electrician !

mmcmdl

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Long story short . Years ago I powered my shop with a 10 hp rotary phase converter . Bought it out of York Pa. from Wilke Mach . I believe for $1700 or so . I have moved and removed several times over these past years never getting the shop re-started . Couple months back I sold a pair of Ports to guy and he told me when I repowered , to go with a VFD . ?????

Could anyone explain this to me in Machinist terms ? I'm looking at probably 10 hp max .
 
I admire your helper. I grew up with them, then in the last 30 years had two shelties. Their loss convinced me I couldn't stand another.
 
We lost this girl back in October . She was our 4rth child . I drove 1425 miles in 26 hrs. two days later and picked up a Sable .
 
How many 3 phase machines do you have and what are the horsepower ratings of each motor?

Are you interested in adding variable speed to a machine?

VFD's have the advantage of adding variable speed but they typically are used with just one dedicated motor. Generally they work out best for motors under about 3 hp. (Yes you can use them for larger motors but they become less cost effective.)

RPC's won't allow speed control but work well with multiple motors and larger motors.

If you still have the RPC my guess that would be your best route. If you want to add variable speed the plot thickens.
 
Thanks Rich . I no longer have the RPC . I will be connecting a 7hp lathe , a 2hp mill with variable speed and possibly my band saw if I can find the space. They are all 3 phase . I will not be running the lathe and mill simultaneously if that makes any difference .
 
The cost of a VFD that will power a 7Hp motor is going to be more costly (~$800-900) relative to a 10Hp RPC that you piece together new parts like a Phase-Craft + 10Hp motor ($600-700 with shipping). The VFD will take up less physical space, might be simpler to install (from a total wiring perspective to meet NEC code) and has some machine specific programmable parameters that have some benefits. There are no de facto single phase VFDs rated for a 7Hp 3 phase motor, so you would need a 15Hp (11Kw) VFD that can run off of single phase in a derated mode (usually divide the the VFD rating by 1.7). Some VFDs will shut down with loss of phase, you need a model that can be run off of single phase in a derated mode. The VFD (depending on the model) on the mill could be run off of single phase or 3 phase from the RPC. Band saw would probably run off the RPC.
 
I would go with the RPC . to use the VFD you would need one for each machine and like someone said the larger ones are not efficent.
 
I seem to remember some time back when the gear head Colchesters went to a variable speed drive . It had zero torque at low rpms . I'm guessing this would be the same case as a VFD driving a gearbox lathe ?
We had VFD's on most of our conveying systems down at my last plant , but torque was not an issue .
 
The issue with a 7 HP lathe is I would bet that it's got a coolant pump, light and other things that run from the main power feed. None of that will work correctly if you are running it on a VFD. It would all need powered from a separate power source, and since you stated that you don't have alot of electrical knowledge I would advise you to not mess with that. You are familiar with using a RPC and that will do what you need to do.
 
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