Level 2 204 3 Phase - Confused ?!? Help !

[Electric_Yoda]

Hi guys

Been given the paperwork and info for our Level 2 204 Application Of Health And Safety.

Basically we have a 3 phase star set up/rig. Supply is 110v. Each phase has a 60W bulb and a 100W bulb.

Been told we must estimate beforehand VL, VP, IL, IP and Total Power, Apparent Power and the Power Factor.

Right ......

VL = 110v

So VP = 110 / square root 3

= 63.5v

Now when I come to work out IL and IP I am getting very confused and could do with a little guidance.

Some of the confusion is because the tutor mentioned that we mustn't forget the bulbs are now running on 110v , not 230v, so power ratings won't be 60W and 100W ?? Is this right ??

Any help really appreciated. I'm bogged down in a mess of power equations and going mad here ! :_|

I'm sure this should be straight forward. Prob looking at it all wrong.

 

[msb2003]

I'll give some of it a go!

If you have VL of 110v then your right that VP = 63.5v

If connected normally (phase and neutral you only have 63.5v) so I'll assume the lamps are connected phase to phase to get 110v as your tutor advised.

With the lamps connected to 230v and using 60W you need to calculate the resistance so you can calculate the current.

So...... P = V squared / R

so....... R = V squared / P

R = 52900 / 60

R = 881.66 ohms

Now using 110v

P = V squared / R

P = 110 squared / 881.66

P = 12100 / 881.66

P = 13.72W

Now to work out the current with 13.72W @ 110v

P = I V

so..... I = P / V

I = 13.72 / 110

I = 0.125 A

You should be able to follow this for the other calculations

Hope this makes sense and helps

 

[Electric_Yoda]

Thanks *SO* much.

That all seems clear and makes sense. Back on track. Think I was looking at it too long yesterday and brain had melted.

Cheers again