Running on a rotary phase converter

682bear said:
I had the same issue with running my 3hp horizontal mill on a 5hp RPC... The motor on the mill drives a hydraulic pump. On startup, it would really pull the RPC idler down for a few seconds. After the mill reached its running speed, the RPC powered it fine. I upgraded to a 7.5hp RPC... it doesn't have any problems starting the mill.

-Bear
Click to expand...
Yeah, sadly a 25hp RPC gets super expensive all at once! I can fortunately just wait a few minutes for the pressure to bleed off (or leave the pump on when I know I'm going to use it in a few minutes), and can avoid having the power-feed on until it is spinning up. That said, it is clear the 20 HP motor is 'the limit' for my machine.
 
Unless you have other machines you plan to use the RPC for, it is a significant expense for a short term solution. You can put together a VFD enclosure with a VFD and wire it up with the basic 1340GT install VFD directions for a less than an store bought RPC. Should just take a few hours. I am not a big fan of static converters on lathes, but if you just need something to run the lathe for a short period of time they are much less expensive, or buy a prebuilt RPC control box and find an idler locally. Ratings on RPC's vary by manufacturer, so always important to match up the recommended RPC to the motor load and probably go one size up if you are planning other three phase machines.

My understanding is the 1236T and 1340GT have the same motor, on my 1340GT it was a 2 Hp, so would recommend going with a 5 Hp idler so something like the PL-5, AR-5, GP5NL etc. You also need to factor in what amperage circuit you have available, a 2 Hp VFD will run fine off of a 20A breaker, and a 5 HP RPC probably 20-30A. I would also look for a 1750 RPM idler and a TEFC or better yet TENV for the lower noise.
 
I guess I need to zero in on my dilemma. I knew this would turn into a RPC discussion and I am ok with that. I enjoy hearing about everyone's setups and advice. But what I would really like to know is: are the advantages of 3PH really worth it? It looks like even the cheapest conversion route is going to be around $600. I can run a 1236T on my 3horse rpc but it will not be handy. It is a plug in setup I built for a few machines I don't use very often. So, those of you who have made the conversion, what is it that you just couldn't live without now that you have it. And vice versa, Anyone have a 1ph and wish they had a 3ph?
 
The machine does not know what the phase power is, I'm on a RPC as I stated, and I went that route for now(VFD ordered) due to the advanced knowledge here supported that route, and there are advantages to that. You will have to dig for the posts for the pros, and cons of each. Maybe someone can refresh some of that information here. If all you want is the machine to work, and the project is not too picky, they will both hit the numbers, there may be finish differences etc., but you can still turn material. You have a great foundation, in the long run after owning the machine you can change over to 3ph, and VFD, it all depends on what your initial needs are.
 
You must log in or register to reply here.
Back
Top