3 Phase Calculations for Star and Delta

[TailSpin]

Hi All

just a question for the more mathematical people.

Have got three 15kw water heaters wired in Star . What is the current calculation for this per phase and would this change if wired in delta assuming a pf of 1 ?

Regards

John :6::rolleyes2:

 

[itselectric]

If you're wiring in star you will have 230v rate heaters assuming mains voltage if you wire in delta you'll have no heaters left assuming 400v across phases.

 

[THE DUKE]

Are the heaters 15kw at 230v or 400v

 

[TailSpin]

I thought they are 400v but will have to check the spec.

 

[Knobhead]

While you're checking the voltage, have a look if there's a neutral to the start point. If there isn't there's all sorts of fun calculations for you to do.
If they turn out to be 230V please don't atempt to connect them in delta. (Seen it done in a gearbox oil heater. Cost £1000's to put right).

 

[TailSpin]

Hi Tony
I know there is no neutral there so I guess it's the calculation time !

Regards
john

 

[malcoa]

Current in star (Ip=IL)=15Kw/((√3)x400x1)=21.6A
Line Current in Delta IL=15kw//((√3)x400x1)=21.6A
Phase Current in Delta Ip=21.6A/(√3)=12.5A

Lucky its balanced

(Pf would be 1 on a resistive load)

 

[Knobhead]

Nope..

 

[Knobhead]

As a hint, you have to calculate the resistance of each element and then transpose the higher voltage due to them being connected in delta.
The reason I asked if there was a neutral, if one fuse blows it chucks a real spanner in the works.

 

[Silly Sausage]

I'm going to observe this from a suitable distance!

 

[Knobhead]

Got a familiar ring, Archy?

 

[Silly Sausage]

Ding ding!
That's you stirring that up.

 

[malcoa]

As a hint, you have to calculate the resistance of each element and then transpose the higher voltage due to them being connected in delta.
The reason I asked if there was a neutral, if one fuse blows it chucks a real spanner in the works.

LOL Sorry, i took a red face for that, ignore that calc, give me 10 mins

 

[malcoa]

How about this one

Current in star (Ip=IL)=45Kw/((√3)x400x1)=65A
Line Current in Delta Ip =45kw/((√3)x400x1)=65A
Phase Current in Delta IL=65Ax√3=113A

 

[Knobhead]

Ding ding!
That's you stirring that up.

Would I ? ? ? ?