Re: [CAD_CAM_EDM_DRO] Re: power supply

----- Original Message -----
From: "mariss92705" <mariss92705@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Thursday, September 12, 2002 12:10 PM
Subject: [CAD_CAM_EDM_DRO] Re: power supply


> Hi,
>
> Besides agreeing with everything Brian said I would also add triacs
> and SCRs can "full cycle". This means they can trigger at the zero-
> crossing in the event a noise pulse trips them off. Not a problem
> with a light bulb but a big problem with a power supply that suddenly
> goes to 160VDC for a cycle or two.
>
> Mariss
>
> --- In CAD_CAM_EDM_DRO@y..., "bsptrades" <bspunkar@a...> wrote:
> > The Triac/ dimmer approach does not sound like a good idea to me
> for
> > voltage limiting.
> >
> > If the Triac fires in quadrant 1or 3 of the AC wave form you will
> > still see the full AC mains voltage on the transformer . You are
> now
> > relying on the fact that the Triac is limiting the "effective
> power"
> > of the AC wave form. This works only because the coil resistance
> and
> > circuit components limit the peak current in the secondary charging
> > the bulk capacitor.
> >
> > For a steady load you can achieve a current balance that works
> well
> > enough but the motor controls are dynamic. As soon as the drives
> > revert to a regenerative braking the current draw drops or
> reverses.
> > This will allow the bulk capacitor to charge to full voltage very
> > quickly as it is being helped by both the AC input and regenerative
> > energy.
> >
> > Limiting the Triac to the falling edge of the cycle Quadrants 2
> and
> > 4 is possible but now your peak current capacity will be very low
> as
> > the "effective" power to the bulk capacitor is well under 50% max.
> >
> > I think this approach will cause problems without a very wide
> safety
> > margin.
> >
> > Brian
> > BSP
> >
> >
> > --- In CAD_CAM_EDM_DRO@y..., "Mike Snodgrass" <snarf@s...> wrote:
> > > On my ongoing search to use easily available and cheap
> solutions...
> > I have several step down transformers that I would like to use as
> > power supplies. The problem is that after inputing 120V I get 82V
> > output after filtering and rectifying. 2V over the threshhold of
> my
> > drive. I installed a easily available light dimmer in the input
> and
> > after applying load I can precisly control voltage. These units
> are
> > rated at 600W, the thyristor in the unit can be paralled to give
> > more current or use a heavier one designed for router speed
> control.
> > I also mounted a cheap VOM in the circuit to monitor voltage.
> > >
> > >
> > > [Non-text portions of this message have been removed]
>
>
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