Re: [CAD_CAM_EDM_DRO] Re: VFD's / Skates, Tim & JohnS.

johnhe wrote:

> >John,
> >Somebody is pulling your plonker. A 1.5Kw Yaskawa invertor RETAILS
> >for £280 and it has a fan already built in. I know I buy loads of
> >these, In fact I'm an agent in the sense of getting a good discount.
>
> =The fan was for the motor, he said as the hertzies drop down and the
> spindle speeds come closer to 500rpm the motor will get hot and eventually
> damage the invertor so the spindle motor needed force vented cooling if I
> wanted to run it at 500 for long periods.
>
> >You really need to do your homework though. 1.5 Kw is 2 Hp, if the
> >motor on the mill is bigger than this then it's no use. You have to
> >match the motor to the invertor.
>
> =I did, the 1.5kW is the power going out to the motor which is 2HP. I didn't
> make it anymore complicated than it had to be and just said "I need 1.5kW
> coming out on triple phase and I'm using single phase to supply it." and I
> let them work out all the bits I'm not so sure of right now. I don't
> remembering being asked the voltage out but they assumed 230v, when I need
> 460v (The motor is rated for 415v I think, is this like how all the stuff in
> the UK is rated for use on 240v but we use 230v?).

You will probably find the 460 V version at a particular power level is
cheaper than the 230 V one. it will be much easier to convert single
phase 230 to 460 than the 3-phase output of the inverter. Also, the
inverter will not run properly (or at all) with a transformer after it. Used
460 V inverters are cheaper, because there is much less secondary
market for them. 220 - 240 v is pretty much the same, the inverters can
handle the entire range. When you program the inverter, you would
tell it that the motor should get 460 V at 50 Hz, and it will scale all other
voltages for the correct frequency.

>
>
> >I can offer you a 2.2kw single phase input unit, brand spanking new,
> >latest model, not a last years clearout complete with programming
> >panel and filters for £300
>
> =Do you have a make for that inverter? I only just found a few places
> selling them, I'm off school tommorow while the teachers show parents around
> so I'll call some of these places and ask. I've felt a grinding halt to my
> plans, the guy wrote back and said he'd plugged it in and the spindle motor
> spins. The spindle bearings are fine he says but the motor's bearings are
> noisey. Fine he says if I plan to buy a new motor otherwise they are cheap
> and easy to replace. Am I about to hear number with three zeros in it?

No, the motor bearings run somewhere around $15 in the US. note that there
are a bunch of small bearings in the head other than the spindle. These are
mostly in the backgear, but also in the power feed. They are generally
even cheaper than the motor bearings, but they add up by number. ALL
the (ball) bearings in the entire head, other than the spindle bearings,
were trashed in my Bridgeport J head. Still, I think it was well under US $100

to replace everything, including the ones in the motor.

Jon