f Control cable length


Control cable length

Q) How do I calculate the critical length on control cable for contactor?
The permissible length of cable (m) can also be calculated by using the formula below:




U : Rated coil voltage

dU : Voltage drop ( 5%)

Son : Coil VA / W at pick up

Cos φon : p.f of coil at pick up

R: Ohmic resistance/cable values as tabulated




When long control cables are used for actuating the contactor, large voltage drop may occur causing chattering of the contactor or even failure to pick up. If the length of the cable exceeds L, use of higher size of cable or use of contactor relay is suggested as shown in fig.




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