Three-phase copper cable 230 V AC between phase and neutral or 400 V AC between phases
Three-phase copper cable 230 V AC between phase and neutral or 400 V AC between phases
Example : Example of a warehouse
Characteristics of the installation
39 x 70 W 230 V sodium vapor lamps with compensation, connected to a three-phase circuit between phase and neutral.
Power factor (Cos ): 0.85.
Average distance from the switchboard: 120 m.
Calculations
Lamp power per phase: (39 x 70)/3 = 910 W.
Ballast losses per phase, estimated at 10% of the lamp power: i.e. 91 W.
Lighting power per phase (P): 910 + 91 = 1001 W = 1 kW.
Corresponding current (I = P/U Cos ): = 1001 W/(230 V x 0.85) = 5.1 A the next highest value in the table, i.e. 6 A is selected.
Correction of the values in the table for the maximum cable length to take the power factor into consideration:
98 x 1.118 = 110 m;
163 x 1.118 = 182 m the corrected value immediately above 120 m in the table, i.e. 182 m is selected.
Cable and protection values selected
The cable cross-section per phase recommended so as not to exceed a 3% voltage drop at the end of the line is therefore: 2.5 mm².
Minimum recommended circuit breaker rating: twice 6 A, i.e. 13 A or 16 A as the standard value.
This rating is in fact less than or equal to the maximum authorized rating (16 or 20 A) to ensure that the cable is protected.
