Relay Coil Supression
Relay Coil Supression
(OP)
When are you supposed to use a suppression device on a relay DC doil? Are there any general guidelines that anyone knows about? In my application, I am using 125 VDC relays with a coil burden of 16 W max. We have placed diodes across these relays in the past, but I am wondering if if its really necessary. There is no digital or solid state equipment affected by the relays and it is not much power. Any help would be appreciated.





RE: Relay Coil Supression
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If we learn from our mistakes,
I'm getting a great education!
RE: Relay Coil Supression
This can create some quite high voltages.
If you control the relay with a mechanical switch, the voltage will keep climbing until an arc is created over the just disconnected switch.
If you are using a solid-state switch (transistor, FET etc.), such an arc is usually only created once. (Burn, Hole through)
The reverse diode across the coil gives the current a way to flow when disconnected, keeping the voltage across the switch to the power supply voltage + 0.65V.
RE: Relay Coil Supression
A L W A Y S.
If "doil = coil".
RE: Relay Coil Supression
David Baird
mrbaird@hotmail.com
Sr Controls Engineer
EET degree.
Journeyman Electrician.
RE: Relay Coil Supression
Chances are, it will never get to the coil contacts (after all this is the reason we use relays - lower control voltage can switch a higher voltage through its contacts). So the statement concerning contacts is invalid. The suppression of arcs across contacts requires another suppression across the contacts not the coil.
If you do a search I have posted many links in another thread talking about what your inquiring about.
RE: Relay Coil Supression
RE: Relay Coil Supression