soft start
 

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

soft start
 

Karl Townsend wrote:

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

Larger idler motor on the phase convertor would probably do it, as would
starting the vertical spindle before trying to start the horizontal so
the vertical motor acts as an additional idler. The VFD is certainly the
best way to go, and you could with appropriate safety interlocks
multitask a single VFD to run either motor (one at a time).

soft start
 

Karl,
I once owned a hydraulic shift Cincinati knee mill with dual spindle motors
as well. Lovely machine. Depending on the motors and the number of wires
available, you could use a two way start switch where you start the motors
in a "Y" configuration and then, when up to speed, switch them to delta for
running under load, but you need 12 wires not 6..
Steve

"Karl Townsend" wrote in message
ews.com...
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

soft start
 

There are two easy and obvious answers:

1) Use a bigger idler (easiest and cheapest by far)

2) Use a VFD (whether it is easy depends on the control system).

i

soft start
 

On Thu, 29 May 2008 11:03:31 -0500, "Karl Townsend"
wrote:

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

How about an idler pulley/simple style "clutch"?

soft start
 

"Karl Townsend" wrote in message
ews.com...
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