Couple of things wrong here. 30 isn't a wire size. If you mean a wire that can carry 30 amps that would be # 10. Now it depends on how many # 10 wires you want to put into a conduit that governs the size of the conduit.
30 amps of current requires at least AWG 10 copper wire. (US NEC)
10 guage
copper wire diameter,length and numbers of turns for 20 micro Henry inductance and 1600 Amp current
can use 400mm THW,RHW,RUH (rating: 400mm = 388amperes)
475 amps, per NEC 310-16. Note that this is a maximum; there are many reasons to derate the current carrying capacity of the wire.
The nearest AWG wire size to 50 sq. mm is 1/0. A 1/0 aluminium conductor with an insulation factor of 75 or 90 degrees C is rated at 180 and 205 amps respectively.
AWG # 6 copper
A # 14 copper conductor will be fine to carry 8 amps at 120 volts. This size conductor is rated at 15 amps.
Need to know the wire size.
A #6 copper wire with an insulation factor of 75 or 90 degree C is rated at 65 amps.
Service wire for 100 amps requires AWG #3 copper.
#8 RW 90 degree wire
# 4 copper wire short distance.
If you mean 2/0 copper wire it is rated 175 amps. # 2 wire is 115 amps. If you are referring to 2.0 metric it is rated 15 amps.
Service wire required is AWG # 3/0 copper.
# 8 RW90
Number 10 thnn copper wire.
14