Long cable induction??? 1

[martinrelayer]

We have a relay that is being activated by an induced voltage (115V) in a long cable application.
The circuit is like this: 230V AC 50Hz source, connected to a long 2G1,5 (1,5 square milimiters) cable (400 meters) connected then to an auxiliary contact, then back to the A1 of the relay, then the relay A2 is connected to neutral. In the installation, the cable is separated from power cables a minimum of 15 centimeters.
When we disconnect from its 230V source, the voltage dissappears.
Then we connect again, but disconnect in the auxiliary contact, well-separating the cables, and the voltage is induced in the same way.
Any hint??

Thanks,
Martin

 

[SteveWag]

Induced voltage can be a problem on long runs. It will go away if DC is used for control voltage.
Steve

 

[Noway2]

A trick that I have used several times in the past on long runs is to place a resistor or capacitor to ground or to the chassis to bleed off the induced voltage. You need to pick a value of sufficient rating to not interfer with the normal operation of your circuit and to withstand when full power is applied. You will probably find that the induced voltage will collapse with even a small capacitor or large valued resistor.

 

[itsmoked]

Please read this.
thread238-217821

Keith Cress
kcress -

http://www.flaminsystems.com

 

[martinrelayer]

Thanks to all... yes I placed another relay in parallel just to get away of the problem, just to figure out a solution later. I'll make some resistor in parallel more or less equal to the impedance of the relay. These are not so good... 230Vac relay activates at 114V... damn!

 

[itsmoked]

Go figger! Half the time I'm wishing a relay would pull in at half its nominal.. And in your case it does and you don't want it to.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[VEBill]

Perhaps such relays should have a little sensitivity adjustment screw.

 

[martinrelayer]

Keith
Go buy Omron's