Last Week of October Question...

[Silly Sausage]

400V 3P Star, NO Neutral.
Loads of 100, 120 & 150 Ohm, purely Resistive.
Star point of supply is Earthed at 0V.


What are...

Current through each Load.
Voltage across each Load.
Voltage to Earth of the Star point.




May add more sub Qs later when I've attempted the answer myself.


The only prize I can offer is Kudos!!!

 

[pennychew]

Is that an aftershave or something?

 

[Silly Sausage]

Is that an aftershave or something?

OK, cut the 'amusing' quips and knuckle down to the question!

 

[pennychew]

OK, cut the 'amusing' quips and knuckle down to the question!

Sorry mate, will do!

 

[pennychew]

Might be barking up completely the wrong tree here but is this what you mean?

Only touched on this a little last year so i know im not strong on it

 

[pennychew]

I even rotated that before i posted it to stop it ending up sideways!

 

[Silly Sausage]

No.

The supply Star point is Earthed (as normal), NOT the Load. Read the Q!

Clue...Floating Neutral

 

[pennychew]

I'm going to have to get back to the books on this one

 

[Simonslimline]

The phase voltages are going to vary due to the unbalanced loading. I need to refresh on this and have a good read first before trying to answer it though.

 

[Silly Sausage]

To be fair, it's not as trivial as it may appear!

Points will be awarded for researching the method to solve it and having a go at the Maths.

 

[happysteve]

I had a think about this after the pub last night, but I didn't get very far. I'd have a punt at the voltage to earth of the star point: I reckon it has a phase angle of 29.8 degrees (assuming 100 ohm load is on L1, and 120 ohm load is on L2). The voltage I'm less sure about: 66V? I'm too embarrassed to show my workings.

As a hint to everyone: is the order in which you ask for bits of information (current through each load, voltage across each load, voltage of star point) related to the order in which you solve the problem, or not?

 

[pennychew]

If Simon and Steve are struggling with this one it will be way beyond me! if you work it out put the workings up so i can get my head around it as well, cheers

 

[ElectroChem]

Ooh, time to look up the lesson on unbalanced star points.

Archy you're an evil man, making me dig into the pit of despair that is my pile of school notes.

 

[Bobster]

Christ, taken me back to working on bitumen heating tanks. The heating elements were all connected in this manner, caused loads of fun when elements failed and it became imbalanced.

 

[Bobster]

Christ, taken me back to working on bitumen heating tanks. The heating elements were all connected in this manner, caused loads of fun when elements failed and it became imbalanced.

I know there is a thread on here, regarding how it's worked out. I think Archy was involved.

That's my little nudge in the right direction.