R, L, C and Power Question

jaydub · Jul 18, 2017

Question: Three coils of resistance 40 Ω and inductive reactance 30 Ω are connected in delta to a 400 V 50 Hz three phase supply. The total power will be:

a) 13.31 kW

b) 7.68 kW

c) 9.6 kW

d) 16.63 kW

I now know what the answer is, however, I do not understand how to get there! I would be very interested to see what others think to this.

I will hold back the correct answer for the time being.

jaydub · Jul 19, 2017

Thanks for everybody's help on this, passed my 2365 302 exam today!

static zap · Jul 19, 2017

Well done !

Simonslimline · Jul 29, 2017

Can you possibly show the working out to get the answer below please?

jaydub said:
The answer is apparently B, 7.68kW.

Would anybody be able to explain how to carry out the calculation? I have looked at the PDF Vortigern, but I still don't understand it...

Simonslimline · Jul 29, 2017

Can you possibly show the working out to get the answer below please?

jaydub said:
The answer is apparently B, 7.68kW.

Would anybody be able to explain how to carry out the calculation? I have looked at the PDF Vortigern, but I still don't understand it...

static zap · Jul 29, 2017

Simonslimline said:
Can you possibly show the working out to get the answer below please?

Read thru post( 7) ... the last good line reads =8Amps
(ignore everthything from then on)

The final answer is 3x the answer for 1 phase , so divide B= 7.68 /3 for clues !
Post (10) has the other formula needed .
" Copper Losses " is probably a good google phrase

(compared with other examples , impedance bits are handed on a plate )
(No Pi , frequency, current etc to get confused/distracted by hunger with )

Simonslimline · Jul 30, 2017

Thanks,

Also would it be corrrect to say that the apparent power of this is 9600VA

With a power factor of 0.8 making true power 7680watts?

static zap said:
Read thru post( 7) ... the last good line reads =8Amps
(ignore everthything from then on)

The final answer is 3x the answer for 1 phase , so divide B= 7.68 /3 for clues !
Post (10) has the other formula needed .
" Copper Losses " is probably a good google phrase

(compared with other examples , impedance bits are handed on a plate )
(No Pi , frequency, current etc to get confused/distracted by hunger with )