Source: company email (Archives/Internal Affairs), 2023-11-08
Facts
Three-phase: P (kW) = √3 × VL × IL. √3 ≈ 1.732. VL (line voltage) is 380 V in most SA installs. IL is current per line.
Example: 7.5 kW vacuum pump → 7500 = 1.732 × 380 × IL → IL ≈ 11.4 A.
Circuit-breaker minimum: CNC machines × 1.25; motors × 1.5 (so 11.4 A motor → about 17 A minimum).
Worked load example: 5.5 kW-spindle CNC router with cooler ≈ 8 kW whole machine, plus 7.5 kW vacuum pump, plus 3 kW dust collector — size the breaker from the summed kW using the formula and the CNC/motor factors above.
