Re: Converter or Inverter for 2hp Bridgeport mill

Bob, what are you using the small motor for? Is this just to start
the rotary converter? Why don't you just add a start capacitor and
potential relay. If you're building a small unit, you could use a
Supco SPP-8E hard start available from www.grainger.com (4MG78).

If you use run caps to both single phase legs and a good motor you
should get a nice generated leg. My generated leg varies about 10V
from no load to full load and the phase angle is pretty good.

~petev

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Bob McKnight"
<bobmcknight@c...> wrote:

> To: CAD_CAM_EDM_DRO@yahoogroups.com
> From: "ibewgypsie" <ibewgypsie@h...>
> Date sent: Sun, 04 Jan 2004 06:50:28 -0000
> Subject: [CAD_CAM_EDM_DRO] Re: Converter or
> Inverter for 2hp Bridgeport mill
> Send reply to: CAD_CAM_EDM_DRO@yahoogroups.com
>
> Hi
>
> am new to the group, so hope this is appropriate.
> The Home Shop Machinist just completed a series on rebuilding the
> Bridgeport.
> I am building a rotary converter and wonder if anybody knows if
> turning the rotary transformer at synchronous speed would help
> even out the current available from each leg. I have a small motor
> with a mechanical variable speed drive that I am attaching to the
> old motor that is the heart of the machine. Also have capacitors
> to help 'tune' the system.
>
> Bob McKnight
> [ Double-click this line for list subscription options ]
>
> I used a toshiba single phase in, 3 phase out inverter. I used the
> bridgeport relay to turn on with dry contacts, left the overload in
> place (overkill since inverter monitors too). I gutted the cnc

drives

> and upgraded at that time too thou. Inverter works great.
>
> My phase convertor made the head rattle, inverter is much smoother.
> Money well spent. I have my machine on a 30 amp 220 single phase
> circuit now. Like I said I upgraded the cnc drives too. The 3 phase
> cnc drive transformer had to go.
>
> David Cofer
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "john_glynn57"
> <john_glynn57@y...> wrote:
> > I have just taken delivery of my own Bridgeport mill and want to
> > know which is the best option for powering the machine : an

inverter

> > or a converter. My research to date suggests that a Hitachi L100
> > inverter is the way to go however I want to question this as
> > follows: 1. I can run a dedicated 20A or 30A supply to the machine
> > which should be able to handle the startup current demand of a
> > converter. 2. If I use a converter I can use all the original
> > Bridgeport systems without mosification ie Bridgeport speed
> > control,forward and reverse,3phase coolant pump and shaping unit
> > which is attached to the machine.
> >
> > My plan is to circumvent the original Bridgeport wiring and drive
> > the Main motor(s) directly from the hitachi unit and setting the
> > motor speed at the low speed of 1400 and not using the valiable
> > speed control of the machine at all. The hitachi will give me

speed

> > control by varying the frequency however I do intend to use the
> > original forward reverse switch. In addition I plan to replace the
> > coolant motor with a single phase model.
> >
> > Am I doing the right thing.
>
>
>
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