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Posted by Don Young on May 29, 2008, 10:21 pm
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> My Supermax has landed. This knee mill has both horizontal and vertical
> spindle motors. They are 5 hp. The vertical spindle will start with my 3
> phase converter system, but repeated start/stop/start/stop will trip the
> breaker. The horizontal spindle trips the breaker unless the drive belts
> are removed. And then it "just" starts. Running load is just a few amps
> and I know I'll never go to full horsepower cutting.
>
> I have a 30 amp breaker on #10 wire going to a homemade "Fitch" RPC. Then
> #12 wire throughout the shop. I can't read the nameplate on the RPC
> motor - I think its a 3 hp.
>
> I'm looking for suggestions to be able to start this mill without a
> complete re-wire job. Some kind of soft start?? larger RPC pony motor??
> I'll consider a VFD only as a last resort.
>
>
> Otherwise, this is one serious mill. I can now look down my nose with
> disdain for those folks using a Bridgeport.
>
>
> Karl
>
>
Since starting is marginal, extra capacitors across the motor leads may
help. You could try just one capacitor across the same two leads as the main
capacitor in the RPC and/or equal capacitors across all leads to help the
start power factor a bit. The capacitors should not have to be disconnected
after starting.
Don Young
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> spindle motors. They are 5 hp. The vertical spindle will start with my 3
> phase converter system, but repeated start/stop/start/stop will trip the
> breaker. The horizontal spindle trips the breaker unless the drive belts
> are removed. And then it "just" starts. Running load is just a few amps
> and I know I'll never go to full horsepower cutting.
>
> I have a 30 amp breaker on #10 wire going to a homemade "Fitch" RPC. Then
> #12 wire throughout the shop. I can't read the nameplate on the RPC
> motor - I think its a 3 hp.
>
> I'm looking for suggestions to be able to start this mill without a
> complete re-wire job. Some kind of soft start?? larger RPC pony motor??
> I'll consider a VFD only as a last resort.
>
>
> Otherwise, this is one serious mill. I can now look down my nose with
> disdain for those folks using a Bridgeport.
>
>
> Karl
>
>