Capicator for relay coil protection

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kody916

Member
Location
Illinois
Generally for long distance control cables, cable capacitance may be sufficient to turn on the relay even when the applied voltage is removed. So connecting a capacitor in parallel with coil can mitigate this effect.
But how to select the proper Capacitor(in micro farads or farads). I mean what factor determines the value of capacitor to be used?
Can anyone reply please.

Thanks
 

kwired

Electron manager
Location
NE Nebraska
The link Smart $ posted discusses using the capacitor plus a series resistor as a method of softening the blow so to speak for transient voltages across switch contacts.

Putting a capacitor in series with a relay coil seems to me would just add capacitance to the conductors that we already have a capacitance issue with according to OP. Seems to me we either need to use different relay coil that needs higher current level before it can pull in the armature or some other method to shunt the capacitively coupled voltage to a level below the pull in level of the armature.
 
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