Does a Rotary Phase Converter Actually Make Real 3-Phase Power?

[Frank S]

My RPC according to anyone you want to talk to is undersized to run even my mill. This is both true and untrue at the same time.
the General accepted policy is to size your RPC at 125% of the motor on the machine you need to power.
When I bought my 3 hp 17-54 LeBlond lathe is came with a 2 HP RPC made by American Rotary I asked the guy about it, and he said that was how it was configured when he bought it and had run it without issues for many years it just didn't instantly start or reverse instantly. So, I ran it like that for 3 or 4 years until I started constructing a power panel for the machine shop 200-amp 24 circuit 120/240v split phase panel added a magnetic starter in an enclosure for the RPC allowing me to switch it on or off from a wall switch. a 12 circuit 3ph 200-amp breaker panel with a main breaker ran the 2 lines to the main breaker and pulled the 3rd leg from the RPC. Start the RPC and have 3 legs of power to the bus bars below the main and 3 pole breakers to each machine.
Now you might think all that is well and good, but you can still only run 1 machine at a time. NOT ALWAYS TRUE. each motor brought online in a sense once it is started and runs up to RPMs becomes and idler adding to the 3rd or wild leg of my panel. I can have my lathe running and switch on the mill and it will start almost instantly. or have the mill running and switch on the lathe and it starts faster. The other day I wanted to bring my 7HP lathe online to check and see if it is going to be a good lather or if I should just sell it Naturally the RPC by itself could not start the much larger motor it just tripped the breaker to the RPC. So I started the mill let it run as a idler motor started the lathe I always use and allowed it to do the same, then made sure the spindle clutch was disengaged on the 22" Leblond the motor spun up as if it were receiving power company 3ph power I reversed it several times engaged and disengaged the spindle a few times and it never faltered so to simulate a load I engaged the spindle clutch and it the start button, it spun right up, not that I would ever start that lathe with the spindle engaged but my 17" lathe does not have a spindle clutch so switch it on and the spindle runs all the time the motor is running just like my mill.
I am building a second PRC to parallel in circuit but don't have all of the Start and run capacitors connected up to assist in starting it and balancing out the line outputs, the second RPC is an 8 hp motor. Once this one is online then I can finish connecting my 9KV step up transformer and have enough 460v to power my layout drill, plus, if need be, I have 2 more of the 8hp motors to put together a 3rd or even a 4th RPC.

[nova_robotics]

Once this one is online then I can finish connecting my 9KV step up transformer and have enough 460v to power my layout drill, plus, if need be, I have 2 more of the 8hp motors to put together a 3rd or even a 4th RPC.

Wait a second. I was busy writing stuff about VFDs and phase converters and totally glossed over the fact that you're adding a 9kV step up transformer to your shop. What on earth do you need 9kV for?

[Frank S]

Wait a second. I was busy writing stuff about VFDs and phase converters and totally glossed over the fact that you're adding a 9kV step up transformer to your shop. What on earth do you need 9kV for?

OOPs the "a" was missed, the 9 KVa transformer weighs about 300 lbs it was with the Cleereman layout drill when I bought it at a Lockheed auction about 25 years ago and was the only way I could boost my then 208 3ph up to the 480 required to run the drill press I could rewire the many motors in the machine to run on the lower voltage but all of the magnetic starter coils would have to be replaced so simpler to buck up the voltage I have a 600v 3ph panel mounted with circuit breakers fed from the transformer for any 480 machine I might need to eventually wire in and 600v disconnect boxes to be mounted near each machine requiring 480 v just like 240v 3 pole disconnects at the lathes all wiring is run in steel conduit with a ground wire for each machine 120/240 single phase in in its conduit runs 208/240 3ph in its own conduit runs and the 480v 3ph in its own runs I don't crowd conduits with conductors and don't mix 3 ph with single phase stuff.
If I ever decide to have 3ph hit my building by the power company, it will be a simple matter to set a meter and hit a 500-amp 3ph disconnect I already am using with 2 200 amp fuses reverse wire a couple panels and it will be good to go

[nova_robotics]

Oh okay. You should have made up a lie because I was looking forward to hearing what wild and crazy project you were doing with 9kv.

You guys have 600v down there? I thought 600v was only a Canadian thing.

[Frank S]

Oh okay. You should have made up a lie because I was looking forward to hearing what wild and crazy project you were doing with 9kv.

You guys have 600v down there? I thought 600v was only a Canadian thing.

For reasons of electrical safety practices, disconnects, panels and any electrical components associated with voltages in or above the 440/460v ranges are required by the NEC to have the higher voltage rating. This is because higher voltages have the potential to produce more powerful arc blow when breaking contact, and can fail to properly disconnect if lower voltage rated components are used.