At a trade show or a concert, one question keeps coming up: how much power can you draw from this socket?
The answer depends on two things: the socket's rating, in amperes, and the supply feeding it, single-phase 230 V or three-phase 400 V.
Back to basics
In France, P17 is the name commonly given to industrial sockets and plugs complying with the CEI 60309 standard (IEC 60309). They come in 16, 32, 63 and 125 A, single-phase or three-phase, and they are the standard for event power distribution.
The apparent power of a socket is simple to work out: voltage × current in single-phase, √3 × voltage × current in three-phase. For example, a 16 A three-phase P17 gives √3 × 400 V × 16 A, or about 11,085 VA, rounded to 11.1 kVA.
Here are our reference figures, at 230 V for single-phase and at 400 V for three-phase:
- 16 A single-phase socket: 3.7 kVA;
- 16 A three-phase P17: 11.1 kVA;
- 32 A three-phase P17: 22.2 kVA;
- 63 A three-phase P17: 43.6 kVA;
- 125 A three-phase P17: 86.6 kVA.
Beyond that, we move on to Powerlock connectors, one per phase, one for neutral and one for earth: a 400 A Powerlock represents 277.1 kVA.
Maximums, not targets
Be careful: these figures are theoretical maximum apparent power, with no diversity factor and no margin. They tell you the most the socket can supply, not what it is sensible to plug into it.
A socket loaded to its maximum leaves no reserve: at the slightest overshoot, the circuit breaker trips. So we always keep a margin between the power required and the capacity of the socket.
Cable length matters too. A cable is a resistance: the longer it is, the greater the voltage drop, and the lower the voltage reaching the equipment at the end of the line. Over long runs, you therefore need a larger cable size.
To sum up, the rating and the supply give the socket's maximum. The diversity factor of your equipment, the margin and the cable length tell you what you can really connect to it.
What a socket can give is not what you should ask of it.