3 Phase Coffee Machine

[dizwoz]

Hi I hope you can advise, I'm looking to buy a used coffee machine, the one I'm looking at is 5.2KW and it's 3 phase, question is: can I conect it to a single phase supply and if not can it be converted? Thanks

 

[Paul_C]

It depends on the heating elements. If they're 240V types and just distributed between the phases to balance the load, then you could wire it for single-phase operation (you might need to be careful about the internal wire size on what was the neutral, since with single-phase it would then have to carry the full-load current).

If the elements are actually 415V types connected phase-to-phase, then you wouldn't be able to run from a single-phase 240V supply without adding a transformer, which would probably end up making the whole idea more trouble and expense than it's worth compared to just finding a suitable 240V machine.

 

[ban-all-sheds]

Unless you drink an unfeasibly large amount of coffee this machine is not going into your private home, is it?

Any other location will have EAWR and/or public liability issues, so please engage the services of a qualified and insured electrician.

 

[matt1e]

Hi I hope you can advise, I'm looking to buy a used coffee machine, the one I'm looking at is 5.2KW and it's 3 phase, question is: can I conect it to a single phase supply and if not can it be converted? Thanks

Usually yes you can
make/model?
details should be on the machine

Matt

 

[Sherbertlion]

...(you might need to be careful about the internal wire size on what was the neutral, since with single-phase it would then have to carry the full-load current).

If it was wired to 3 phase supply then surely it wouldn't have an internal neutral wire? Not for the heating elements at least.

 

[Paul_C]

If it was wired to 3 phase supply then surely it wouldn't have an internal neutral wire? Not for the heating elements at least.

It would with 240V elements.

 

[Sherbertlion]

I presume you are assuming that the 3 elements were each connected individually to each phase with their own neutral then and not linked across each other?

 

[Paul_C]

I presume you are assuming that the 3 elements were each connected individually to each phase with their own neutral then and not linked across each other?

If they're 240V elements they would have to be wired phase to neutral (yes, in theory they could be wired in wye configuration without a neutral being connected, but practical constraints make that rather unlikely).

If the element is wired across two phases then it would have to be a 415V element. I'm not sure if that's what you meant by "linked across each other" though.

Edited to add: All assuming that this machine is actually built for the U.K. or European markets with 240/415V (or thereabouts) wye supply systems.

 

[dizwoz]

Hi All

Thanks for the replies and discussion, looking at what you've said I gambled a little and bought the machine, took it to a coffeed machine specialist and yes it can be converted quite easliy, which is where currently sits. Cheers

 

[matt1e]

Glad you got it sorted op.

On another note

I presume you are assuming that the 3 elements were each connected individually to each phase with their own neutral then and not linked across each other?

If they're 240V elements they would have to be wired phase to neutral (yes, in theory they could be wired in wye configuration without a neutral being connected, but practical constraints make that rather unlikely).

I see a lot of 3ph elements these days in various equiptment and most the time they are connected star (they are really 3x 230 v elements in the same housing)
sometimes they have a neutral connected and sometimes they don't
In case of element failure its makes for a better system if the element star point is connected to neutral if available (as paul has basically stated)

Matt
















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[Sherbertlion]

So how would the elements be physically connected?

If star, would one end of each element be connected to a common point with the other end of each element connected to L1 / L2 & L3? And if this is the case I presume you could potentially connect a neutral to the common point?

If delta, one end of each element connected to one end of the next, essentially putting all 3 elements in series then one phase to one terminal of each element?

 

[Sherbertlion]

If the element is wired across two phases then it would have to be a 415V element. I'm not sure if that's what you meant by "linked across each other" though.

Yes, that is what I meant. Just trying to visualise how they would be physically connected...as my questions above.

 

[matt1e]

So how would the elements be physically connected?

If star, would one end of each element be connected to a common point with the other end of each element connected to L1 / L2 & L3? And if this is the case I presume you could potentially connect a neutral to the common point?

If delta, one end of each element connected to one end of the next, essentially putting all 3 elements in series then one phase to one terminal of each element?

yes correct but in the star connection the neutral will carry no current if all the elements are ok so as its not needed in this situation it's sometime left off
but if an element goes open circuit then its desirable to have a neutral otherwise the remaining two elements will lose some power as they will have less voltage running on two phases alone

Matt

 

[Paul_C]

Yes, that is what I meant. Just trying to visualise how they would be physically connected...as my questions above.

With 415V elements, the three are connected:

1. L1 - L2
2. L2 - L3
3. L3 - L1

With 240V elements, the three are connected:

1. L1 - N
2. L2 - N
3. L3 - N

As mentioned above, the actual connection to the supply neutral can be omitted, leaving just one end of each of the three elements connected together at the star point. In theory, perfectly balanced elements would result in no neutral current anyway, hence the connection can be omitted. In practice, there is bound to be a small neutral current since it's impossible to make all three elements exactly the same. And as Matt has explained in more detail, the neutral will then carry more current if one of the elements burns out.

 

[Sherbertlion]

In practice, there is bound to be a small neutral current since it's impossible to make all three elements exactly the same.

How does this work if the elements are connected in Delta?

Another question...! What is the difference in the physical make up of a 230V element and a 400V element and, I suppose the same question & answer would also apply to a 230V or 400V motor winding?