Answer / kh

3 core is used for 3-ph loads/systems which do not require
neutral e.g. motors. 3.5/4 core is used wherever 1-ph
supply is also required (tapped between 1ph-N) in addition
to 3 phase supply. 4 core used for smaller cables usually
upto 16 sqmm where neutral core is of same size as phase
cores while 3.5 core is used for higher sizes where neutral
core is half the size of phase cores.

Answer / at

3 core cables are used where ever the system is ungrounded.

3.5 core cables are used where the major load in an
industry / plant etc. is three phase but also has single
phase loads or loads that can cause a little unbalancing
and thus the nutral might carry some current but not always
and not as much as the line current. Therefore a smaller
cross section of nutral can solve the purpose as current
through nutral will be very small as compared to the rated
current of the cable.

4 core cables are used in systems where all loads are
single phase or majority loads are single phase. so there
are chances of high degree of unbalancing. and nutral has
to carry a larger amount of current.Therefore half cross
section of nutral may not solve the purpose and we opt for
4 core cables. This arrangement is used for small cross
section cables used in homes and industries. for lighting
and other small applications.

Answer / pawan mishra

3.5 core cables contain 4 cores i.e. 3 for phase and 1 for
neutral.
it is known as 3.5 coz it s netral thickness is half the
diameter of phase core.
netral is requried only in l.t. network

Answer / p.k.chadhar

3 core cable can be used for three phase power supply
without earthing
3&1/2 cable can be used for three phase power supply with
earthing because 1/2 core is mostly used for earthing or
gounding
4 core cable can also be used for three phase power supply
with earthing this cable can also be used for control supply
it depends on size of the cable if it is 1.5 mmsq.then
control ,if size is more can be used for power connection.

Answer / ashok

4 core cables are used for the rating more than 5KW,and the
3 core ,31/2 are used for below 5kw and 5kw supply.

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