Hello, I am an Engineer with basic electronic knowledge.
Today i was disconnecting a faulty break coil (24VDC) on the end of a motor drive, accross the terminals was a RC suppressor. This was stright forward stuff but there was an area of confusion i would like your electronic expertise to clear up.
I always thought RC suppressors were for AC only, Diode suppressors for DC and Varistor for both.
Am I correct and the wrong suppressor is fitted or am i totally wrong?
Thanks in advance for your replies.

 

Putting a rectifier across a DC relay coil slows the release so much that the contacts have a tendency to weld. Putting a Zener (Transorb) across still clamps the spike, but dissipates the coil energy faster (because the forward drop is so much higher than a simple diode) getting the relay armature moving faster, minimizing the contact welding problem. An RC snubber consisting of a lowΩ resistor in series with a DC blocking Capacitor is yet another way to dissipate the coil energy fast but hold the voltage to the coil current times the resistance.

 

Thanks for the info...
But is a RC suppressor for AC only,
And a Diode Suppressor for DC only.
If this is the case can fitting the wrong one by mistake cause a problem.

Thanks

 

Thanks for the info...
But is a RC suppressor for AC only,
And a Diode Suppressor for DC only.
If this is the case can fitting the wrong one by mistake cause a problem.

Thanks

No, an RC snubber is frequently used on DC relays powered with DC! It is actually better for the relay than a diode snubber, and equivalent to a Transorb.