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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