cable sizes

[bugsy]

Havent got regs with cable tables to hand but we installed a 50kw induction oven about a month ago and it was protected by 125a mccb .

The reason I asked about the load is because if you look at the cable tables for current / VDPM will see that it's different depending on the load.

 

[james king]

i take the cable you used was not 95mm lol? yes i relaise that but the Q does not state it im sorry! it says the machine is a bio fuel machine!!!

did you install the mccb into the 3phase CU then run SWA from there to a isolation point and connect the flex up in the out going of the isolator? just wondering how much big loads work

 

[bugsy]

I think you will find 70mm will fit the bill and should you not be calcing @ 400v

 

[i=p/u]

aye maybe , multicore says 95 squared and single core 70

 

[bugsy]

L.V switch panel MCCB to 125a switch disconnector and no the final connection was not in flex

 

[james king]

ok u used a 70mm 5 core cable? that must be huge. so my answer of 16mm is way to small

 

[james king]

so ypu came out the distribution boards in to a lv switch panel to 125a isolator have you got a diagram i am very interested in massive cables and industrial

 

[pushrod]

Is the 50 kW figure total power or power for each phase? Have they said if there is a power factor involved and whether it is connected in star or delta?

 

[james king]

50kw power intotal: No power factor as i know of. No i do not know if its delta or star! If in delta you would not need to carry a nuetrul to the isolator would you?

 

[pushrod]

50kw power intotal: No power factor as i know of. No i do not know if its delta or star! If in delta you would not need to carry a nuetrul to the isolator would you?

correct,no neutral if in delta.

power=√3 x Vl x Il

so rearrange to get Il which will be your design current Ib

 

[james king]

does that mean even though the DB has a N you still do not need to bring a N to the machine??

and say you have 1x 3 phase (100A per phase) CU with say umm 12 ways and you want to run this 50kw load from this supply..

how does switch panel work and does it run of the DB eg

DB - switch panel - from SP to the mccb then from there to the isolator?

 

[pushrod]

No practical expert by any means but if it is a motor connected in delta there will be no neutral - it will be a balanced load with no resultant neutral current.

Forgot to say before that your power per phase willbe a 1/3 of the total power, still use the √3 though.

reckon your line current in each phase is 24A if ihave used this rubbish windows calculator properly.

edit Il (line current) will be 72A as does not need dividing by 3 - reason you are dealing withtotal power, line currents and line voltages, not Ip and Vp and power per phase

 

[james king]

so if each phase is carrying 24A then a 70mm cable will not be needed. i have taped in a cable calculot on the net and it come up with 16mm. im very confused about what to put and how i got 16mm and some one came up with 70mm??

so what cable will i need?

 

[pushrod]

you also need to take account of grouping and ambient temp -you got an OSG with you?

 

[james king]

yes i do mate