Re: Changing over to VFD and 3 Phase Motor

--- In CAD_CAM_EDM_DRO@yahoogroups.com, hannu <hvenermo@...> wrote:

>
> The vector duty and inverter duty motors are meant for very low

speeds,

> about 10 hz down to 1-2 hz.
> Basically, they will not overheat
>
> You are very unlikely to need these very low speeds, about 10-30

rpm,

> with a mill drill.
> You could use a normal motor and a small computer fan to keep it

cool.

> They are better motors, will live longer, turn smoother - none of

which

> matters with a mill drill. The case bearings, duty cycle, mass etc.

of

> the machine is fairly light - both motors will perform the same in

a

> mill-drill.
>
> So, in a nutshell, you don´t need it.
>
> You would need a vector duty motor if;
> you mount a spindle position sensor i.e. encoder.
> You direct drive your spindle as a servo drive.
> This would allow you to do direct, rigid tapping. Here your rpm and
> rotational speeds go down to zero.
>
> This is a very advanced (and for some, a VERY useful thing)

feature, and

> less than 1% of e.g. mach sw users use it.
> For production, involving tapping, it would be great.
>
> My non-inverter duty 3-phase runs really well to 15 rpm. But it is

a

> very good 3-phase motor (bridgeport).
>
>
> Torsten wrote:
> >
> > Finally made up my mind to change over to 3 Phase with a VFD for

my

> > Mill-Drill Machine.
> > I got a good deal on a GS2-22PO Drive from Automation Direct.
> > I should be able to controll the Spindle Speed from the CNC-

Controller

> > with this Drive.
> > Now I need to replace the single Phase Motor with a 3 Phase 220

volt

> > Motor.
> > A lot of advertisement about Vector Duty Motors and Inverter Duty.
> > These Motors are considerably more expensive.
> > Are they really worth the extra Cost?
> > I assume that those features will give a wider usable range of

Spindle

> > Speeds without changing Belts.
> > Is it worth the difference or just a bunch of marketing?
> >
> >
>

Thanks for the input everyone.
I think I will stick with a regular 3Phase Motor.
I can always add some Fans to the intake to give it extra cooling.
A example of the low range would be to Tap with a 3/4-10 Tap at 100
RPM.
Still requires some torque to drive this into steel.
Top Speed maybe 2000 rpm where I can not envision needing much torque
at all.
I have no plans to do any ridgid Taping, I will be using a floating
Tap Holder using G84 Taping cycle.
Just need to find the proper Belt position to give me this kind of
Speed Range without needing to change the Belt.
Anybody know sources or brands for a good Motor resonably priced?