Re: 3 phase motor math

Thanks for the explanation Jon,

I've seen inductance come up before in discussions of brushed DC
motors and Geckodrives.
How difficult is it to measure motor inductance ?

Rab

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
>
>
> rainnea wrote:
>
> >How important is it to match the VFD to the motor ?
> >Can using a motor with a higher or lower inductance than the VFD
is
> >designed for cause damage to either ?
> >
> >
> Yes. A motor with too little inductance can draw huge currents, and
> may pop transistors in the VFD. As long as the inductance is
within the
> right range, the overcurrent safety circuits can respond in time.
With
> too low an inductance, the current can rise so fast the transistors
get into
> thermal runaway and secondary breakdown before the current sense
> circuit can shut it off.
>
> >I was hoping to use an old AC servo motor to power a spindle, so
my
> >main concern is if the VFD will spin the motor without blowing
either.
> >
> >
> Well, it depends. If the motor has current, voltage and HP ratings
similar
> to the VFD's ratings, it most likely will work.
>
> Jon