3 ph 415v AND a neutral ??

[0831]

i am installing a large three phase generator (inner cables are 240mm feeding a 630 amp breaker) see pic. in the panel on the genny there are 3 phases plus another connection to the side of the breaker in the pic which i am lead to believe is a neutral connection, this feeds power a control panel which in turn is controling various motors and and a soft start inverter there is no neutral connection in the main control panel, in the past i have just used installed a 4 core swa and used one of the cores as a main earth connection to the main earth on the main control panel so what am i to do with this extra neutral? connectionm i assume it is there should one require to use one of the phases with a neutral? mmm i am having difficulty getting the manufactures to talk to me about any of it what do you guys think?

 

[waross]

Your grounding scheme will often connect to the neutral bar beside the breaker. High impedance ground, low impedance ground, direct connected ground.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[0831]

thanks for your comment, i guess what i really want to know is - do i connect the fourth core ( using it as a main earth to the control panel)of my swa to the bar at the right of the phases in the pic ( the other end to the main earth in the control panel) or do i connect it to the main frame of the genny and then to the main earth on the control panel? what/where is the difference?

 

[waross]

Is this a stand alone system?
How do you deal with grounding issues on the main system?
Your system or plant grounding philosophy will determine to a great extent how your neutral is connected.
If you ground the neutral at the panel of an ungrounded system or an impedance grounded system you may have a direct system ground through the generator.
The grounding of the generator neutral should harmonize with the system grounding scheme.
Is your system star or delta?
Is there any grounding arrangement on the system?
Is there a transfer switch involved?
Is your generator islanded or paralleled with the utility?



Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[0831]

thank you waross!, this is a mobile crusher, all the equipment is mounted on a large flat bed trailer.
the main feed comes from the generator mounted at the front of the trailer some 7 feet in the air, it is 3 phase 600 see photo for the amp rating of the main switch on the genny.
a 185mm 4 core swa feeds a main control panel from the genny, a 3phase supply from the panel to a soft start inverter which feeds a 160kw motor.
there is also a 45kw oil pump motor which is a star/delta connection from the control panel and a small 2.2kw motor i assume to be wired in delta in the control panel, these motors drive various conveyors.
The genny output gives me 3 phases plus this extra connection (neutral?) i am using a 4 core 185mm swa that feeds the control panel from the genny, i am considering using this neutral as the main earth using one of 4 cores that goes to the control panel, i will also provide a 95mm tri rated earth cable from the genny mainframe to an earth stake in the ground (if needed on site)

 

[waross]

I am assuming that there is a ground bus in the main control panel. Connect the neutral to this bus and connect your ground rods to this bus also. You will have a grounded wye system.
The equipment will not know the difference between delta and wye.
All equipment frames must also be connected to this ground bus. That is any conveyors or similar equipment that is powered from this genset but are mounted on their own trailers and not mechanically connected to the main trailer.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[0831]

thank you for all your comments, I have now dismantelled the generator set, it is also mounted on the same framework as all the motors ( delta and star/delta run on this trailer) i have trace what appeared to be an unmarked neutral which is bonded to an earth cable of the same size (approx 240mm trirated single) and the other end of that earth is bonded to the framework, i was pretty sure that it that the "odd" neutral would go to earth somewhere but the connection was buried deep within the genny.
so, the fourth core is in fact now an earth feeding the control panel which is also bonded to the framework as is the soft start inverter and all the motors, all i can say is i lost time on the install due to an unmarked "spare" neutral which was in fact connected to earth, thanks also to waross for a good reply, hopefully i won't have to many probs in the future but i am very thankful and pleased that you were all there for me on this one! speak soon