? Zener diodes safely/effectively used in series?

Thread Starter

mjdx9

Joined Dec 17, 2003
2
Hi All,
Excuse my etiquette, this is my first post.

I have a relay coil flyback problem. Relay response timing is critical and an RC circuit delays relay response to unacceptable limits.

The circuit is 270VDC, and I can only find Zener diodes to 200VDC.

Can I stack zener diodes in series to achieve the required voltage?

Any suggestions, experiences or comments welcome.

Thanks in advance.

Martin
mjdx9atyahooo
 

Dave

Joined Nov 17, 2003
6,970
If you can only find Zener diodes that operate up to 200V and you are operating at 270V, it would be very dangerous to use them due to the problems of voltage breakdown and runaway current. A zener will operate happily as a voltage regulator at the specified voltage and within the tolerance stated; usually between 5% and 10%.

Like Battousai says why not just look at a transformer.
 

Thread Starter

mjdx9

Joined Dec 17, 2003
2
I am not trying to create a power supply, I am trying to limit a voltage spike that occurs from a collapsing electrical field from a coil on a relay.
the contacts which open the circuit running the 270VDC relay arc badly when opened since an approx. 1400V spike is generated from the inductive power of the coil. The intention is to quickly short this current without delaying the contact opening. An RC circuit works, but slows the relay close-to-open (make to break) time beyond a critical acceptable limit. A zener would essentially look like an open circuit until the spike exceeds the zener voltage, then would conduct to eliminate the arcing and dissipate the stored energy in the coil...

Sorry I wasn't more clear in the first post...
 

hatvmt

Joined Dec 25, 2003
1
Perhaps I'm reading your question incorrectly! In the trade we fit a diode across the coil of the relay, so that the collapsing (field) B.E.M.F. will be bypassing the coil via the diode back into the supply rail, therefore only the level of the supply rail should(!) be the max!
 
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