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Home Shop Phase Converter

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garrettec2011

Plastic
Joined
Jan 3, 2012
Location
Centerville Ia
Hey Guys,

I finally purchased a mill and lathe for my home shop and I have a few questions regarding phase converters.

The lathe is 7.5 hp but has a clutch. Do I still need to buy a 15 hp rotary phase converter?

The mill is 1.5 hp. If I purchase a 15hp phase converter will this be too large for the mill?

Thanks for your input!!
 
I'll vouch for the diy rpc panels from the guy out of Yamhill, Or. I have his 20hp and 30hp panels running in parallel(when needing the power) and doing great.
 
crickets said:
What's the advantage of an RPC over a VFD ?
Click to expand...

Well, the OP asked about a RPC so answered his question.

I put VFDs on almost all my machines - variable speed control. Even nice on a knee mill - don't have to adjust belting. I did NOT put it on a Leblond servo shift -machine already has variable speed.

Upside of RPC - 3 phase machines ready to go as built and inexpensive.

VFDs give variable speed and make machine plug into single phase if needed. Depending on machine can be quite a rewire job to get going.
 
crickets said:
Any chance you have a scope picture of that effect ?
Click to expand...

Ask and ye shall receive...(I seem to recall purple was the manufactured leg)

3phase.jpg


The critter in question:

Conv.jpg


How it was measured:

3phase_setup2.jpg
 
- Bigger the RPC idler, the harder it is to START. Two or more smaller idlers, stagger-started or not even both/all always used can work.

if using low voltage wire to 7,8 and 9 only or 1,2 and 3, jump 4,5 and 6. One or the other so motor starts at 1/2 HP rating. then when running use a contactor to connect the other 1/2.
 
In my opinion, a VFD on anything larger than 3 HP just doesn't make economical sense.
Big dollars for a good quality (reliable) unit *that will run the motor at full power*
 
madmachinst said:
wow those phases look beautiful. Within what %? You had to mess a lot with caps?
Click to expand...

No capacitors were harmed in the making of that converter. It's totally, 100%, validated capacitor-free. Even the pony motor there is repulsion start, induction run.
Key factor being the idler motor at 5 hp is very much larger than any of the load motors. The pony motor btw is 1/8 hp.
 
Per the OP questions...........

The bigger the RPC the better, in general. With an RPC, the larger size just produces better power.

With a VFD, a larger than needed one costs a lot more, and the overcurrent protection may not be able to be set to protect a much smaller motor.

VFDs require much of the internal control system in the machine to be removed or disabled. An RPC is plug-and-play with zero change to the machine unless it needs a voltage conversion (which you'd have to do anyway).
 
Another question I know a motor repair guy ( real great guy next time I visit must bring 6 pack). He was concerned that he was always taught only use Wye connected motor for RPC. I am stuck with 50 hp delta. Am I looking forward to any problems? Otherwise he said that this idea over here in post #43 ( second drawing)

3 phase starter circuit

should work real fine. Come guys I need some more verification before I start buying the remaining parts. Please.
 
so basically I should have gotten a bigger motor. The only disadvantage I saw in Wye vs Delta is the heat dissipation according to that thread. If necessary could parallel another motor that fires up after start up would that alleviate that problem or not? All I am running on that 50 hp delta is a CNC Mazak ( lathe) SQT 18-MS Big spindle 20 hp con. 25 int. Other item is a retrofit V2XT CNC BP that I might add fuses for a third phase and step down transformer for UPS for computer. I'd go 3 phase w/ that so that I can decrease my amperage. Then the Bridgeport clone that is it for now. All this when I have 3 (POCO)wires running through my property. That CNC lathe is why I went with as big a converter as possible so I can keep it in balance and such.
 
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