380 volt 50KW induction heater that won't turn on

[wwhitney]

The Europeans use different terminology than the North Americans do when describing earthing.

So in that terminology, the US typical case might be called TT-C-S? Wired like TN-C-S but with a customer earth electrode connected at the PE/N division point, so it is TT. If I understand correctly.

Cheers, Wayne

 

[wwhitney]

Yes, usually. There are some examples when it is not.

That was a question, if there's a local earth electrode, what is it connected to, on this 380V 3-wire delta system?

Cheers, Wayne

 

[Besoeker3]

That was a question, if there's a local earth electrode, what is it connected to, on this 380V 3-wire delta system?

Cheers, Wayne

To a local earth but directly. I'm trying.....

 

[Barbqranch]

Is the secondary of the transformer connected to the local earth conductor? If so, to which connection? Or is it floating?

 

[Besoeker3]

Is the secondary of the transformer connected to the local earth conductor? If so, to which connection? Or is it floating?

The industrial systems I have dealt with usually have several/many transformers.

 

[wwhitney]

To a local earth but directly. I'm trying.....

OK, if you stick the electrode in the local earth, and connect nothing to it, then it has no purpose. So you connect a wire to the local earth electrode. Where does the other end of the wire go?

In particular, you say 3 phase 380V Delta is used to connect up industrial machines. Are there just 3 wires going to the machine, or is there also a 4th wire for PE? Assuming a PE, the answer to the question above about the earth electrode might be:

A) It's connected to PE only, and the 3 phase 380V Delta conductors have no fixed voltage relationship to PE/earth (there's no other connection)
B) It's connected to PE and one of the 3 phase 380V Delta conductors, so now that phase is 0V to ground, and the other phases are 380V to ground (in the US, that's called corner grounded delta)
C) The transformer that is supplying those 3 phase 380V Delta conductors actually has a wye secondary. The neutral point of that wye is connected to the earth electrode, and to the PE. But the neutral point is not otherwise used as a circuit conductor, all the loads are 3 wire delta. (You might call that a wye supply / delta distribution). So if you measure the voltage from any of the 3 phase conductors to PE, you'll get a steady 240V, but there's no provision to supply 240V 2-wire loads.
D) Other?

Cheers, Wayne

 

[Besoeker3]

OK, if you stick the electrode in the local earth, and connect nothing to it, then it has no purpose. So you connect a wire to the local earth electrode. Where does the other end of the wire go?

In particular, you say 3 phase 380V Delta is used to connect up industrial machines. Are there just 3 wires going to the machine, or is there also a 4th wire for PE? Assuming a PE, the answer to the question above about the earth electrode might be:

A) It's connected to PE only, and the 3 phase 380V Delta conductors have no fixed voltage relationship to PE/earth (there's no other connection)
B) It's connected to PE and one of the 3 phase 380V Delta conductors, so now that phase is 0V to ground, and the other phases are 380V to ground (in the US, that's called corner grounded delta)
C) The transformer that is supplying those 3 phase 380V Delta conductors actually has a wye secondary. The neutral point of that wye is connected to the earth electrode, and to the PE. But the neutral point is not otherwise used as a circuit conductor, all the loads are 3 wire delta. (You might call that a wye supply / delta distribution). So if you measure the voltage from any of the 3 phase conductors to PE, you'll get a steady 240V, but there's no provision to supply 240V 2-wire loads.
D) Other?

Cheers, Wayne

PE?

 

[wwhitney]

Isn't PE (Protective Earth) what you call the bonding conductor (we call it EGC) that connects together non current carrying metal parts of the installation? E.g. the metal chassis of equipment, any metal conduit carrying conductors, etc.

Cheers, Wayne

 

[wwhitney]

Really, the original question about your 3 phase 380V delta was if you stick an earth electrode into the ground next to one of your machines, and you measured the voltages from each of the 3 phases to the earth electrode, would they all be 240V and stay stable?

If so, then somewhere upstream, possibly at the transformer secondary suppling the system, there's a neutral conductor for your 3 phase conductors, and that neutral conductor is connected to an earth electrode.

If not, if the voltage readings would change over time, then your 3 phase 380V delta is floating relative to earth (what we would call ungrounded).

Cheers, Wayne