Calculation in amperes on three-phase
vertacos12
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Hello,
I haven't found a better forum and section.
I bought a 15 kW workshop screw compressor in 400V+N+Earth. The salesperson told me that I need to install a 40 A four-pole circuit breaker for protection. What do you think about this? Because if I look back at the forum, it says to calculate as follows: 15 x 1.5 = 22.5 amperes per phase. Since there are 3 phases, that totals 67.5 amperes overall.
Now I'm not sure what to do to purchase the equipment for the panel. Also, how should the subscriber's circuit breaker be set, at 40, 60, or 90 amps?
Thank you for your help.
I haven't found a better forum and section.
I bought a 15 kW workshop screw compressor in 400V+N+Earth. The salesperson told me that I need to install a 40 A four-pole circuit breaker for protection. What do you think about this? Because if I look back at the forum, it says to calculate as follows: 15 x 1.5 = 22.5 amperes per phase. Since there are 3 phases, that totals 67.5 amperes overall.
Now I'm not sure what to do to purchase the equipment for the panel. Also, how should the subscriber's circuit breaker be set, at 40, 60, or 90 amps?
Thank you for your help.
Hello,
Power is calculated as follows:
P = U x I x cos(fi) x square root(3)
In alternating current, you must take into account the phase shift current/voltage => cos(fi)
For this motor, we will assume cos(fi)=0.8
In three-phase systems, you need to multiply by the square root(3)
This gives I=P/(U x cos(fi) x square root(3))
= 15000 / (400 x 0.8 x 1.73) = 27.12A