Power phase question.

[DeaD_EyE]

Our 3~ AC Powersupply looks like this:

def plot_sine(Ueff):
    max_voltage = Ueff * math.sqrt(2)
    x = np.linspace(0, np.pi * 2, 3600)
    x_time = np.linspace(0, 1/50, 3600)
    plt.xlabel('Time in ms')
    plt.ylabel('Voltage in V')
    plt.title('Time vs Voltage at 50Hz 3~AC')
    for n in range(3):
        roll = -(3600 // 3)
        y = np.sin(np.roll(x, -n*roll))
        y *= max_voltage
        plt.plot(x_time, y)
    plt.legend([f'Phase {p+1}' for p in range(3)])
    plt.show()

Result:    


The DC (direct current) Power supply don't have a phase.
If you draw them in a plot, you'll have straight lines.

If you measure the power against +12V and +5V, you've a difference of 7V.
Usually the devices are connected to one power lane and ground.
Each lane has the reference potential to 0V (ground).

If you compare this to our 400V 3~ net, the earth and neutral conductor is the reference ground.
The difference is, that it's alternate current and the 3 phases are shifted by 120°.

400V is Ueff, the effective voltage. The maximum peak is Ueff * math.sqrt(2).
To calculate Ueff to neutral conductor: Ueff / math.sqrt(3)

If you go further and add capacitive/inductive load, voltage and current have also a difference in phase.
At the end you'll see in a plot negative and positive power. It's used for example to feed power back to the net.
In industry you don't want to have blind power. They compensate the inductive part with big capacitors.