2007-12-17 06:58:37 · 5 answers · asked by martinanderson23 1 in Science & Mathematics ➔ Engineering
As with all electrical conditions, it depends on many things. Is the load on your system all 3 phase and are all of the legs balanced with each other?
If all 3 legs are balanced, and the resultant voltages are equal, there is no current in the neutral leg, hence there is no problems that an undersized neutral will develop in this system.
If the loads are not all 3 phase, rather a single phase of any voltage configuration, the neutral must be properly sized for the whole system. Also any electronics involved on a 3 phase system will sense the resultant 5th and 8th harmonics in the neutral leg and develop adverse symptoms in their applications.
The best solution is to consult a electrical contractor who has an electrical engineer on staff that is familiar with the specific applications of your system. Good luck. Jim.
2007-12-17 07:28:20 · answer #1 · answered by Jim W 7 · 0⤊ 0⤋
Depends how you are defining undersize
Because you are talking about a 4 wire system, any amount of load could be connected to phase and neutral. in fact all of it could. In this case the neutral would need to be bigger than the phase conductors.
You need to determine what load will be single phase and size the neutral accordingly. If you don't then you will have the same effect as undersizing any other conductor.
Any 3 phase loads don't require the neutral so obviously don't count in the neutral sizing.
2007-12-17 16:15:51 · answer #2 · answered by Poor one 6 · 0⤊ 0⤋
By undersize, I assume you mean undersize compared to the 3 phase feeds? Thats ok, and code allows it, provided your neutral is properly grounded. Remember, the newer GFIC circuits and breakers will trigger with the undersized neutral conductors; they are so sensitive that even a one-inch length difference in wires will exceed the milliamps difference in current! That is why the old time house wiring that used two hot wires on a single phase neutral lead-in cannot handle the GFIC circuits!.
2007-12-18 01:02:25 · answer #3 · answered by alaskasourdoughman 3 · 0⤊ 0⤋
Yeah it really depends...you'll have to provide more details.
Ideally, assuming Y connections, and a balanced load, the neutral wire has NO CURRENT. Realistically, this is probably not true, because 3 phase loads are never completely and perfectly balanced.
2007-12-17 18:47:01 · answer #4 · answered by solo 3 · 0⤊ 0⤋
As with any under sized cable you run the risk of over heating and failure of ground fault relay protection.
hope this helps.
2007-12-17 15:13:36 · answer #5 · answered by java 4 · 1⤊ 1⤋