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Electrical Load Assesment - Total demand

Former Community Member
Former Community Member

Hi everyone,

Can you guys make some light into my head, please?

I have gotten very confused on how to do a load assessment for, let's say a building, that would have single-phase consumers as well as three-phase consumers. For this purpose and for easy understanding let's say we have sockets on single phases: L1 - 10A, L2 -12A, L3 -10A, and a three phase consumer of 30A. Can somebody show me a calc for getting the total demand in KVA please?

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    A three phase supply is generally provided on the assumption of a balanced load. So a 120 Kva supply can supply up to 40 Kva on each phase.
    Providing a three phase supply of less than 120 Kva for a load with 40 Kva on one phase will result in overloading one phase.

    Or consider it in amps. A three phase cable, or transformer, or alternator rated for say "150 amps" means not exceeding 150 amps on any phase. It does not mean "an average of 150 amps" it means no more than 150 amps.

    On small supplies to say a dwelling, unbalance is virtually inevitable as many single phase domestic appliances are used largely at random.

    On a large supply to say a big factory or a large apartment block, then care should be taken to balance the loading as equally as possible.
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  • 0
    A three phase supply is generally provided on the assumption of a balanced load. So a 120 Kva supply can supply up to 40 Kva on each phase.
    Providing a three phase supply of less than 120 Kva for a load with 40 Kva on one phase will result in overloading one phase.

    Or consider it in amps. A three phase cable, or transformer, or alternator rated for say "150 amps" means not exceeding 150 amps on any phase. It does not mean "an average of 150 amps" it means no more than 150 amps.

    On small supplies to say a dwelling, unbalance is virtually inevitable as many single phase domestic appliances are used largely at random.

    On a large supply to say a big factory or a large apartment block, then care should be taken to balance the loading as equally as possible.
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