Re: [CAD_CAM_EDM_DRO] Powerdump relay (now with free arcwelding)

Hi Abby,

This is a common problem with DC at higher voltages. Check the
documentation for your relay carefully. You may find it is only rated at
24V or someting. Try using a contactor instead of a relay. Contactors
are normally designed for switching heavy 3 phase motors and can also
handle quite high DC voltages. They tend to have fairly hefty coils so
you may have to turn it on with a relay rather than directly from your
breakout board.

Les

Abby Katt wrote:

>Hi all,
>
>I have a RELAY configuration on my PSU whereby the power being shut off
>(E-stop / limits / etc) causes the transformer to be disconnected and
>the capacitor to be dumped through a power resistor. The problem I am
>getting is that the relay has been arc-welding itself in the ON-Position
>(and lately in the off-position).
>The old RELAY was rated 20A, and the PSU was a 55V/500W linear one, with
>the power resistor calculated to dissipate 10A.
>
>I'm about to install a relay rated at 30A N.O and 3A NC (The best I can
>seem to find for this voltage range) and was wondering if I could use
>some of the capacitors I have spare for preventing DC brush-motor
>spikes, to somehow limit the arcing?
>
>Any advice?
>Thanks!
>Abby
>
>
>

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