N2 Electrical Trade Theory|The Easy Way!


11


Solution: (a) V = V1


___ 3


= 380 3


= 219,4 V 1.4.2 Type of load


Te type of load affects the size of the current that flows through the conductors supplying the load.


When supplying a non-reactive (i.e. a non-inductive or non-capacitive) load, the current is in phase with the voltage (cos ϕ = 1) and the current of the load is simply the power divided by the voltage,


∴I =


P amperes V


In the case of an inductive load it is of utmost importance to consider the actual current “ I “ (which is the current that actually flows through the conductors) and not the active component of the current, “ I cos ϕ “. Since power in an alternating circuit is,


P = V × I cos ϕ, the current required to supply a given amount of power will be;


∴I = P V × cos ϕ, amperes


Tis is the current to be considered when calculating the size of the cable which is to supply the load. Refer to power factor, section 1.3.3.


(b) V = Vsupply


– 5%


= 219,4 – 5% = 208,4 V


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