Re: 3 Phase rotary converters

Another benefit is that it will auto restart
(depending on the type of contactors you use) in the
case of a power failure. For example, you're working
in your shop in the evening and the power fails. You
decide to call it a night and forget to disenguage the
phase converter contactor (assuming you're using a
manual one) and leave. Later the power comes back on.
With the potential relay, the phase converter starts
back up instead of sitting there allowing the magic
smoke to excape and maybe starting a fire. Of course,
you're machine/s will also start back up if you forgot
to switch them off, too.

I use one with my 7.5 hp unit and I'm very happy with
it. My old 2 hp unit used a manual temporary contact
push button contactor to bring the start cap in. It
worked OK but this is better. I just flip the switch
like a light and it's on!

Doug

--- Beau Beaufait <boeman1@...> wrote:

> Using a potential relay, and starting caps is easier
> to set up and would
> appear to be safer than the starter motor and belts.
> Doesn't dim the lights
> and takes only about 0.5 second on my setup. A
> added plus is if you happen
> to stall one of your machines and pull down the line
> voltage the potential
> relay will kick back in and give you added
> capacitance to get the machine
> pulled back up too. Not a recommended situation,
> but it will work. Have
> stories of a working machine shop starting and
> running 10hp + machines on a
> 5 hp converter, utilizing this method. I don't
> recommend it but it will
> work. (rule of thumb, is the phase converter should
> be as big as your
> biggest starting load, but can run up to 3 times its
> size in total hp load,
> as each 3 phase motor running is also like another
> converter on the line)
> Also, I have started a converter with just
> unbalanced run capacitors on the
> line, starts kind of slow, but it will.
>
> Beau
> ----- Original Message -----
> From: <bobmcknight@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Sunday, May 08, 2005 6:56 PM
> Subject: Re: [CAD_CAM_EDM_DRO] 3 Phase rotary
> converters
>
>
> >I am running a rather large motor (10 Hp) and
> decided
> > that the easiest way to start it was to mount a
> 1/2 hp
> > motor and belt connect it to the rotary convertor.
> To
> > start, I turn on the 110v 1/2 hp motor and tighten
> the
> > sliping belt with a handle on the idler pulley.
> This only
> > takes a few seconds. When the rotary motor comes
> > up to speed, I release the handle and the belt
> slips.
> > then I switch on the single phase power to rotary
> convertor
> > and it goes on its merry way. No high starting
> current, or
> > prolonged waits for the convetor to come up to
> speed.
> > I just have the run capacitors to the third leg.
> I could deal
> > with the mechanical starte a lot easier than going
> thru all
> > design and experimentation. I use it to run a 300
> amp MIG
> > welder which will never see close to that output,
> but it was
> > dirt cheap and in excellent condition. I also
> have a 17" lathe
> > that can use either a static or rotary convertor,
> and a 10 grinder.
> > So if you have a small electric service to your
> shop and don't
> > want to dim the lights while starting the
> convertor, there is an
> > alternative.
> >
> > Does anybody know for sure about the voltage
> rating of capacitors?
> > I read someplace that the voltage printed on the
> capacitors is not
> > the voltage that they should be operated at on a
> rotary convertor.
> > A capacitor for a 220 VAC rotary convertor should
> have approx
> > 370 volts printed on its case. ???????
> >
> > Bob McKnight
> >
> >
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> subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC
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