Vernon Tuck
Stainless
- Joined
- Oct 26, 2008
- Location
- Brenham, Texas
I have a couple of 3 phase motors available to use to build a bare bones RPC.
One of these is an 1155 RPM 7 1/2 HP motor. I had it reconfigured for 230V 3 phase and had the motor shop install new bearings while they had it.
Then, I happened upon a deal in a couple of identical Dayton 1755 RPM 20 HP motors.
I don't remember the name plate amps for the 7 1/2 HP motor. But the 20HP motors are rated at 53 amps.
I seem to recall somebody in here explaining that the single phase breaker that feeds the RPC has to be significantly larger than the nominal amperage stated on the data plate.
Could somebody give me a rule of thumb here? I have a 200 amp single phase service available. I would like to start with the 20 HP motor but can't afford a 3 phase breaker distribution panel at the moment. So, I might play with the smaller motor first.
In any case I would appreciate some guidance on how to properly size the breaker that feeds the RPC. The load motors will be a 2HP spindle on a Gorton tracer mill plus a 3HP motor that drives the hydraulic power unit. So that's a total of 5HP.
Both the spindle motor and the HPU motor appear to be wired to a common bus in a fuse box mounted to the side of the machine. What I hope to do is wire the 3 phase output from the RPC directly to the fuse box. Of course I will start the mill and the hydraulic motors separately.
Anyway, I'd like to know what the appropriate size single phase breaker would be for either motor. I will spin the motors to their design RPM with a pony motor before flipping the breaker.
Also, on a slightly different topic but in regard to the same project: I have 3 phase magnetic starter on a Bridgeport mill that I no longer need as the Bridgeport is now powered by a 3 HP Hitachi VFD.
Jim Rozen has mentioned the hazards of locked rotor faults resulting from power failures and then the power coming back on.
Can a 3 phase magnetic starter be wired into single phase 220? The idea would be to salvage it from the Bridgeport and place it between the single phase feeder panel and the RPC for the purpose of preventing it from automatically starting back up after a power failure.
So, in this regard, my questions are:
a) Can I use a 3 phase starter on single phase? and,
b) Does it have to be "sized" to the motor? The magnetic starter controlled a 2HP Bridgeport spindle motor. In this new application it would be starting either the 7 1/2 HP or the 20HP RPC, which in turn would be driving 2 motors totaling 5 HP.
Is this starter an er... "non-starter?"
Thanks,
Vernon
One of these is an 1155 RPM 7 1/2 HP motor. I had it reconfigured for 230V 3 phase and had the motor shop install new bearings while they had it.
Then, I happened upon a deal in a couple of identical Dayton 1755 RPM 20 HP motors.
I don't remember the name plate amps for the 7 1/2 HP motor. But the 20HP motors are rated at 53 amps.
I seem to recall somebody in here explaining that the single phase breaker that feeds the RPC has to be significantly larger than the nominal amperage stated on the data plate.
Could somebody give me a rule of thumb here? I have a 200 amp single phase service available. I would like to start with the 20 HP motor but can't afford a 3 phase breaker distribution panel at the moment. So, I might play with the smaller motor first.
In any case I would appreciate some guidance on how to properly size the breaker that feeds the RPC. The load motors will be a 2HP spindle on a Gorton tracer mill plus a 3HP motor that drives the hydraulic power unit. So that's a total of 5HP.
Both the spindle motor and the HPU motor appear to be wired to a common bus in a fuse box mounted to the side of the machine. What I hope to do is wire the 3 phase output from the RPC directly to the fuse box. Of course I will start the mill and the hydraulic motors separately.
Anyway, I'd like to know what the appropriate size single phase breaker would be for either motor. I will spin the motors to their design RPM with a pony motor before flipping the breaker.
Also, on a slightly different topic but in regard to the same project: I have 3 phase magnetic starter on a Bridgeport mill that I no longer need as the Bridgeport is now powered by a 3 HP Hitachi VFD.
Jim Rozen has mentioned the hazards of locked rotor faults resulting from power failures and then the power coming back on.
Can a 3 phase magnetic starter be wired into single phase 220? The idea would be to salvage it from the Bridgeport and place it between the single phase feeder panel and the RPC for the purpose of preventing it from automatically starting back up after a power failure.
So, in this regard, my questions are:
a) Can I use a 3 phase starter on single phase? and,
b) Does it have to be "sized" to the motor? The magnetic starter controlled a 2HP Bridgeport spindle motor. In this new application it would be starting either the 7 1/2 HP or the 20HP RPC, which in turn would be driving 2 motors totaling 5 HP.
Is this starter an er... "non-starter?"
Thanks,
Vernon