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Siri
03-20-2009, 12:12 AM
I need some advise :

I am using a PROP to drive a SSR(Crydom DNO063 - specs attached) and from extent of my knowledge I don't think I require a spike suppressor
accross the inductive load ---> SSR electrically isolates the prop.
The SSR data sheet state to use a diode across the inductive load.
Should I use a diode or not.

I also have a Transient voltage suppressor diode - part # 1.5KE200CA - bidirectional ( specs attached) - If am to use a suppressor diode can I use
the one I already have.

Thanks

Siri

Beau Schwabe
03-20-2009, 12:49 AM
Siri,

Use the diode. Even though you are isolated from your Prop to the inductive load, your SSR is not, and it needs to be protected by using the diode.

The forward voltage might be a little high for using the suppressor diode... I would go with a standard schottky diode with a forward voltage of .3V to .7V

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Beau Schwabe (mailto:bschwabe@parallax.com)

IC Layout Engineer
Parallax, Inc.

Siri
03-20-2009, 05:02 AM
Beau,

Thank you very much for the quick reply.

Regards ,

Siri

Siri
03-20-2009, 09:00 PM
Beau,

I forgot to ask you - If I drive 110AC motor via the SSR - do I still have to use the snubber diode?

If so what type of diode would I use.- since it is AC not DC. ? bidirectional.

Siri.

TreeLab
03-20-2009, 09:04 PM
Siri : the SSR that you referenced is only for DC switching. If you want to control an AC motor you need an AC SSR, with no diode.

Cheers!
Paul Rowntree

Siri
03-20-2009, 10:04 PM
Paul,

Thanks - I forgot to mention that I was thinking about a SSR - with AC control.

Regards,

Siri

Beau Schwabe
03-20-2009, 11:40 PM
Siri,

For an AC load on an SSR, make sure that the SSR can handle an inductive load. Internally (to the SSR) this would be a back-to-back diode arrangement with a low reverse breakdown voltage causing a "Zener" effect. Since most Zener diodes that I have seen have a low current tolerance, it would be better to find an SSR appropriately rated for your AC load.

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Beau Schwabe (mailto:bschwabe@parallax.com)

IC Layout Engineer
Parallax, Inc.

Siri
03-21-2009, 01:49 AM
Beau,

Thank you very much for advise.

Regards,

Siri