4 Core Cable

What?

In a cable sizeing table there is used 4 core pvc cable for a 30kw ,415v, 62 A ,3 phase 3 wire connected motor feeder.Hence I got confused why using 4 core because systen having no neutral connection.Do u have a answere

http://lmgtfy.com/?q=four+wire+3+phase+wiring

The 4th wire is to confuse the unknowing.

I followed the link to Google and found an answer on the first item that was confusing. It was on a blog/forum and the first reply was that it was an earth, this was rebutted and the poster insisted it was a neutral to give 277v.

I know the fourth conductor as an earth wire ( green and yellow ). If a single phase 240v line is required a fifth conductor is included. We even have 5 pin plugs so that the one machine can have 415v for the motor and 240v for the control, lighting, switching etc. If multiple 240v devices are required then the load is shared between phases so as to not unbalance the 3ph lines. Our plugs and sockets are made so that a 10amp plug will fit into a 10 OR 20amp socket/outlet but not the other way round. Also a 4 pin plug will fit into a 5 pin outlet but not the other way.

Jim

I agree with JIMRAT clarification.

3 Phases and a neutral, (earth). Never has been anything else in all these years of dealing with cables for LV systems. MV, HV, EHV can be 3 phase conductors, or one.

The NEC and the CEC requires a GROUNDING conductor to be carried with all 3 phase circuits.

This is not to be confused with the GROUNDED (neutral) conductor.

If you do not know the difference, don't feel too bad,there are many experienced

electricians that still get the terms confused.

Google the terms for further explanation.

Well, if the 3 phase motor is installed on a ship for instance, they can get away with just using a 3 core cable which surprised me, they can use the ship as an earth on AC systems and the same goes for DC systems If the DC system is rectified after passing through an isolating transformer as they are so dam strict on every other part of the electrical wiring on a ship. I only yesterday learned this, as a for the next month I am commissioning plant on a super Yacht (141 Meters) in Abu Dhabi.

So if it is not to be used on a ship, the forth core has to be the earth conductor.

Cheers

Joe

In fact U can use it for earthing, but in our case all the factories are rigged in 5 cores. Because many motors although 3 phase have single phase coils in their starters, thereby rq a neutral. And many electronics nowadays in the control panels.

Do not confuse Neutral with Ground.

Or vice-versa.

Do not confuse GROUNDING with GROUNDED, or GROUND, as defined by the NEC

Google for the difference.

I cannot begin to tell you all that you need to know, but I can point you in the right

direction:

Dig a little,learn a lot.

I usually see power cables with 4 cores in LV system.