06-29-2012, 02:37 AM
(This post was last modified: 06-29-2012, 02:48 AM by Hopefuldave.)
Andy,
"I did read that I might be able to run the motor with a run capacitor rather than a complete speed control unit? "
This can work with *small* 3-phase motors (e.g. coolant pumps), but is a pretty poor way to get a larger motor working - google "static phase convertor" and you'll find that for sensibly sized motors there are all kinds of other bits (contactors, voltage-sensing relays etc.), as the capacitor value needs to change with load, which on a shaper is going to be twice per stroke - eek! The results aren't so hot, the phase relationship *isn't* 120-degrees between phases, and the "phase" voltages aren't equal - often not even close! This loses one of the big benefits of a 3-phase motor, the smooth torque delivery which *does* have results in surface finish quality etc.
A small (e.g. 1KVA power-output) "hackable" 415V 3-phase-in VFD might be the best way to go (no need to open up the motor and dig out the star pint or add extra wires out to reconnect in delta) - mine (5HP derated to 3HP as I'm running it single-phase in, an old ABB ACS300 series) cost me all of £25 with a bit of Ebay-ninja exercise, the "hack" cost me about 50p... For that and some head-scratching over the control circuits and VFD programming I have infinitely variable speed, soft-start to be gentle to my 60-year-old machine and its irreplaceable motor, instant reverse (not needed on a shaper!) etc.
Just my ha'pennorth,
Dave H. (the other one)
"I did read that I might be able to run the motor with a run capacitor rather than a complete speed control unit? "
This can work with *small* 3-phase motors (e.g. coolant pumps), but is a pretty poor way to get a larger motor working - google "static phase convertor" and you'll find that for sensibly sized motors there are all kinds of other bits (contactors, voltage-sensing relays etc.), as the capacitor value needs to change with load, which on a shaper is going to be twice per stroke - eek! The results aren't so hot, the phase relationship *isn't* 120-degrees between phases, and the "phase" voltages aren't equal - often not even close! This loses one of the big benefits of a 3-phase motor, the smooth torque delivery which *does* have results in surface finish quality etc.
A small (e.g. 1KVA power-output) "hackable" 415V 3-phase-in VFD might be the best way to go (no need to open up the motor and dig out the star pint or add extra wires out to reconnect in delta) - mine (5HP derated to 3HP as I'm running it single-phase in, an old ABB ACS300 series) cost me all of £25 with a bit of Ebay-ninja exercise, the "hack" cost me about 50p... For that and some head-scratching over the control circuits and VFD programming I have infinitely variable speed, soft-start to be gentle to my 60-year-old machine and its irreplaceable motor, instant reverse (not needed on a shaper!) etc.
Just my ha'pennorth,
Dave H. (the other one)
Rules are for the obedience of fools, and the guidance of wise men...
(Douglas Bader)
(Douglas Bader)