4HP is 3kW?What amps does the motor draw?
415v 3 phase so 3 live wires.As ever on the internet, there are different opinions....
In an ideal world, no 1.5mm is not sufficient. Assuming the volts are 240 and the cable should be 1.5 x the full motor load for safety.
P=V*I therefore P / V = A
(4hp = 3Kw)
3000 / 240 = 12.5
Load x Safety Factor = Rating:
12.5 x 1.5 = 18.75A
In that case yes, the cable including safety rating is 10.8A so 16A is within spec.415v 3 phase so 3 live wires.
In my earlier example I omitted the power factor as all my designs used the motor rated plate value x 1.5 regardless of phase structure. In industry, as you know, copper is cheap compared to machine down time. Either way the cable Fizzy has would be within spec to run the motor. I personally wouldn't use it but that is a choice not a scientific reasonI(A) = 1000 × P(kW) / (√3 × PF × VL-L(V) )
KW=hp X 0.75
A= 1000x3 /(1.72*0.9*415)
4.6a per phase
Nope.Do any of these calcs take into consideration startup current or longer leads
Bob
Mine did for start up. I use the industry standard of rated plate x 1.5 but I also said I would not use 1.5mm on a motor regardless as for the length you would need to do the voltage drop calcs (mV/A/m) too.Do any of these calcs take into consideration startup current or longer leads
Bob
Any reason not to use 1.5? I’ve seen loads of motors wired in this in factories all over, and most of my machines are Can’t say I’ve ever seen a problem where the cable sizing was an issue, unless it was too small in the first placeMine did for start up. I use the industry standard of rated plate x 1.5 but I also said I would not use 1.5mm on a motor regardless as for the length you would need to do the voltage drop calcs (mV/A/m) too.
Any reason not to use 1.5? I’ve seen loads of motors wired in this in factories all over, and most of my machines are Can’t say I’ve ever seen a problem where the cable sizing was an issue, unless it was too small in the first place
If its within spec then I’m curious as to what the issue is?
As part of my job, yes I have specified the cable that is (as in this case) within the parameters. For my home shop I over spec the copper to avoid any issues. I have just wired in my dedicated 32A welder supply in 6mm2 where 4mm would 'do'.Any reason not to use 1.5? I’ve seen loads of motors wired in this in factories all over, and most of my machines are Can’t say I’ve ever seen a problem where the cable sizing was an issue, unless it was too small in the first place
If its within spec then I’m curious as to what the issue is?
This is also a factor in many industries. I have been bound by factory minimum spec for certain installations.agreed, I like a comfortable margin to be sure as well, but if it's within spec, why not? or are we oversizing now, because if some's good more's betterer?
A lot of oil companies spec electrical wiring and cable size way over the electrical industry requirement demands, for example instrument power wiring minimum of 2.5mm², but that in it's self can create problems with the size of terminals in some instruments, which leads to difficulties to terminate correctly, so I'm not convinced it's always better.
^^ exactly this - if he didn't already have it and there wasn't much price difference between the next size up then it might make sense to go with a bigger size, however as it's effectively "free" and within spec then it'd be mad not to make use of what's there.There is the actual use consideration, and 'what you have on the shelf' consideration.
Fizzy already HAS the 1.5 mm !