Re: [CAD_CAM_EDM_DRO] VFD Selection

george_barr wrote:

>I want to get a VFD for my Hitachi M12V router so I can vary the
>speed for metal, aluminum, and wood milling. The M12V is a single-
>phase series commutator motor, 115VAC, 60HZ, 15 Amps router. I would
>like to use my 120VAC outlet for the VFD. Can someone tell me what
>kind of VFD I should get? I have noticed some VFD have 3 to 1 phase
>conversion and all sort of specifications. I certainly do not want
>to buy the wrong one. Also, it should interface to my pmdx.com break
>out board.
>
>

Routers generally are either "universal" motors, with brushes, wound
armatures and
field coils running on AC, or DC motors, sometimes with permanent magnets,
running on rectified AC. VFDs only work on AC induction motors, and
are only made for 3-phase motors.

A VFD absolutely will not work with a brush-commutator motor. There are
some speed controllers for routers, but I think they only work well with
the DC-PM motors, as these will hold a pretty constant speed if a constant
voltage is supplied. The series motor you mention above will vary its speed
depending on load. The only way to get constant speed operation from a
series motor is with a closed-loop speed controller, which uses a tach
of some
sort to measure motor speed.

Jon