Re: [CAD_CAM_EDM_DRO] Re: why not just change the motor?

Given the choice of using a VFD or trying to find a flange mounted single
phase motor with an extended shaft, I know which one I would choose.

Pros & cons of a single phase motor:
IF one could be found to fit the hypothetical Bridgeport... The contactors
would need to be replaced. There would be a high startup current that may
trip the mains breaker (so that would need to be uprated).
I would only get one fixed speed (1480 RPM approx).
Reduces the resale value of the machine.

Pros & cons of a VFD:
Needs a dual voltage motor.
Established and reliable technology.
Soft start, so no high startup currents.
DC injection braking.
Full overload protection for the motor.
Simple low voltage controls for on/off
Variable speed from 0 to 2X (depending on the motor).
Simple forward/reverse control.
Reasonably priced units available.
No need to replace contactors as these are bypassed.
Does not affect the resale value of the machine.

A VFD is both simple and cheap, and far from being a kludge/bodge. Three
phase motors and VFD packages are regularly being sold fitted as standard to
a number of machine tools by OEM manufacturers.

Regards, Paul.

On Friday 23 January 2004 3:41 pm, jlsmith269 wrote:
> Or, heck, let's get to the heart of the issue, if *I* bought a 2 hp
> boss 8 cnc, 3ph, I would NOT bother with a vfd on it.. i would get the
> wiring and motor from a 2 hp 220 1ph , and bolt it on... and yeah, I
> would spend DOUBLE or more for that simple solution, rather than
> kludge it, knowing I am introducing unknowns into a pc-cnc/enc setup.

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