Re: [CAD_CAM_EDM_DRO] Re: gecko's and voltage

It isn't so much that the motors need 90V but that step down
transformers are inexpensive and big. I've got 3 servo motors to power
rated at 6A continuous at 90V. These motors are rated at 20A peak. That
is a power draw of 1,5KVA continuous under heavy loads and 4.5 KVA
peak. I'm having real trouble finding a decent transformer to handle
those sorts of loads.

I can easily buy a 1.8 KVA step down transformer from my local
electrical wholesaler.

BTW: I'm an electrical engineer, so I fully understand the Safe
Operating Area with MOSFETS. I did a power design this spring that used
high power MOSFETS.

Kim

On Sat, 2003-07-05 at 15:20, Lee Studley wrote:
> When I first joined the group I was on this rant too, The design for
> higher voltage is complicated and will at least double the costs of
> these drives. Really take it from my experience, you really dont need
> to run those motors to the max @90v. Try hooking it up to a car
> battery and see how much torque just at 12volts. I serioulsy doubt
> you'll ever need the top end speed at 90v under real-life conditions.
> -Lee
>
> Check out for my previous msg:
> http://www.electrical-contractor.net/ubb/Forum15/HTML/000058.html
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Kim Lux <lux@d...> wrote:
> > We need to petition Gecko to make their drivers work with 90+Volts.
> > Many of the good servo motors are rated for 90V and step down
> > transformers offer very good VAs for the money.
> >
> > Kim
> >
> >
> >
> > On Sat, 2003-07-05 at 14:56, Lee Studley wrote:
> > > Hi Kim,
> > > I ran into the same issue in retrofitting my Bridgeport. You need
> to
> > > drop the primary voltage in this case somewhat, and my solution
> was
> > > to add a autoformer. This is a fixed varaic type transformer that
> is
> > > compact, since the 'dropping' winding carries most the current.
> It is
> > > a non-isolated transformer that drives the primary of your
> > > transformer.
> > >
> > > Another way os to add a series bucking transformer winding which
> is
> > > actually made by making a regular transformer act like the above
> > > mentioned autotransformer. ***Be careful*** with whatever you
> try,
> > > and us a variac to bring it up so you can measure output current
> and
> > > voltage. Its easy to hookup the winding backwards and it will add
> to
> > > your primary and boost the voltage. This may exceed your filter
> caps
> > > rating.
> > >
> > > There are plenty of these transformers at air conditioner places
> to
> > > drop 240 to 203 volts and can be used if rated properly. The
> > > impedence isnt perfect as they are made to run at 240vac, but it
> > > will work in practice. The inrush current is higher.
> > >
> > > -Lee
> > >
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, Kim Lux <lux@d...> wrote:
> > > > I sent them an email about the same thing, but bigger voltage.
> > > >
> > > > I'd like to use a HD 240/120 stepdown transformer to supply
> some
> > > servo
> > > > motors. Using 120V as the source, we get 60V AC output, which
> is a
> > > bit
> > > > under 85V DC when rectified. Furthermore, the power around
> here
> > > runs
> > > > higher than 120VAC. I've measured 87VDC on the output of the
> power
> > > > supply circuit.
> > > >
> > > > I haven't received a reply from them yet and I sent that email
> a
> > > week
> > > > ago.
> > > >
> > > > Kim
> > > >
> > > >
> > > > On Sat, 2003-07-05 at 11:27, cnchomeman wrote:
> > > > > I bought some gecko320's. My powersupply
> > > (transformer/bridge/cap)
> > > > > measures 80.8 volts no load. This is a whole .8 volts over
> the
> > > max.
> > > > > Anyone have any comments on this? I am currently running on
> 65
> > > volts
> > > > > (my transformer has a few taps). I would like to try the
> 80.8
> > > volts,
> > > > > but am new to gecko's and don't want to let the smoke out.
> > > > >
> > > > > Eric
> > > > >
> > > > >
> > > > >
> > > > > Addresses:
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> > > > Kim Lux <lux@d...>
> > >
> > >
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> > >
> > > OFF Topic POSTS: General Machining
> > > If you wish to post on unlimited OT subjects goto:
> aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach
> it if you have trouble.
> > > http://www.metalworking.com/news_servers.html
> > >
> > > http://groups.yahoo.com/group/jobshophomeshop I consider this
> to be a sister site to the CCED group, as many of the same members
> are there, for OT subjects, that are not allowed on the CCED list.
> > >
> > > NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY
> POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO
> EXCEPTIONS........
> > > bill
> > > List Mom
> > > List Owner
> > >
> > >
> > >
> > > Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
> > --
> > Kim Lux <lux@d...>
>
>
> Addresses:
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>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
--
Kim Lux <lux@...>