Purpose of 110V 3 phase?

Note the terminology used in that table to describe the sockets: 2P+E or 3P+E, not 1P+N+E, and the requirement for protection to be DP or TP. This suggests that a single-phase supply derived from the 110V 3-phase is delta connected and both wires of the single-phase circuit are lines. This is the standard configuration for reduced low voltage 3-phase, 110V line-line and 63.5V line-neutral or earth, the highest permissible voltage classified as RLV.

As per @brianmoooore there is a definite advantage to using 3-phase for motors of any size, but increasing with the size of motor. If a particularly large pump is needed in this application, a single-phase option might be unavailable, costly or undesirable technically.

Lucien Nunes said:

Note the terminology used in that table to describe the sockets: 2P+E or 3P+E, not 1P+N+E, and the requirement for protection to be DP or TP. This suggests that a single-phase supply derived from the 110V 3-phase is delta connected and both wires of the single-phase circuit are lines. This is the standard configuration for reduced low voltage 3-phase, 110V line-line and 63.5V line-neutral or earth, the highest permissible voltage classified as RLV.

As per @brianmoooore there is a definite advantage to using 3-phase for motors of any size, but increasing with the size of motor. If a particularly large pump is needed in this application, a single-phase option might be unavailable, costly or undesirable technically.

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Ever since post #1, the reference to a 400V/110V transformer was really bugging me, as the 400V (I assume) is phase-to-phase, and 110V, while a familiar number, should in this context surely also be the phase-to-phase voltage, meaning, as you mention, the L to N is 63.5V. I wasn't aware that is a valid value, albeit the highest, for RLV.
Thank you for the contribution - I can now cease my puzzlement!

James said:

Split phase is not the same as single phase.
split gives you 2 phases 180degrees apart.

single phase obviously has no phase difference angle.
3 phase has 3 x phase voltages 120degrees apart.

your original post is about 110v 3 phase
however you have just mentioned that you are talking about 110v from phase to earth is this 3 phase? If so then it would be about 200v phase to phase.

a drawing or spec sheet would be really useful at this point.

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That is incorrect! Two phases 180degrees apart would give you zero volts phase to phase. It actually is single phase. A phase with the opposite polarity, i.e. 180 degrees apart, is not the same as a second phase. If you take a 110 volt secondary winding with a center tap and make the center tap ground or neutral, you now have a single, split phase. 55 volts from each leg to ground and 110 volts across both hot legs. If the two legs were not in phase with each other, then the voltage across both would be less than 110 volts.

James said:

Split phase is not the same as single phase.
split gives you 2 phases 180degrees apart.

single phase obviously has no phase difference angle.
3 phase has 3 x phase voltages 120degrees apart.

your original post is about 110v 3 phase
however you have just mentioned that you are talking about 110v from phase to earth is this 3 phase? If so then it would be about 200v phase to phase.

a drawing or spec sheet would be really useful at this point.

Click to expand...

That is incorrect! Two phases 180degrees apart would give you zero volts phase to phase. It actually is single phase. A phase with the opposite polarity, i.e. 180 degrees apart, is not the same as a second phase. If you take a 110 volt secondary winding with a center tap and make the center tap ground or neutral, you now have a single, split phase. 55 volts from each leg to ground and 110 volts across both hot legs. If the two legs were not in phase with each other, then the voltage across both would be less than 110 volts.

180 degrees apart. split phase.

electricnova said:

I am looking to understand 3ph 110v.

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Same as other 3P systems, just a different voltage.
Is it that you have trouble with 3P in general, or only with 3P and 110V at the same time ?

However, this thread has made me question my understanding of 110v not 3ph (not sure what to call it at this point).

Why is it that manufacturers refer to 110v as single phase? I have attached examples

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In general, a motor doesn't care whether a 1P supply is split phase, one end earthed, or any other combination. All it cares about is having an AC voktage between 2 wires.

Consider this. You are presented with 2 wires and gave no earth reference. You can measure the voltage between the wires - but you don't know much else.
Is it ungrounded - i.e. a floating supply like you'd get from a shaver socket ?
Is it 110V with one end earthed ?
Is it 55-0-55 with the centre tap earthed (technically split phase) ?
Is it two legs of a 3P supply (of which, there are different ways of earthing, or not, part of the supply) ?

As to what people call it, there is "much confysion" - and even people who should know better can be sloppy with terminology.
In particular, with a 55-0-55 supply, what it us depends to a certain extent on how many wires you have. With 2 wires it's single phase, if you have access to the centre tap then it's split phase. With a split phase, if you connect across the two lines (and ignore the centre tap "neutral"), then that's single phase for that connection.