transformer efficency problem

[capemoff]

hi all

i have been asked the question ( below ) and cant find the formula anywhere any help would be greatly appreciated.

a transformer has a rated power of 24kva and a power factor of 0.95 and the losses are 1400 watts

calculate the overall efficency.

 

[Andy™]

24KVA x .95= 22.8KW

loss is 1.4KW, so 21.4KW output

Efficiency% = (OUTPUT/INPUT)x100

so 21.4/22.8x100 = 93.85%

 

[capemoff]

many many thanks

 

[capemoff]

so how would it be if

a transformer has a rated power of 1kva and a power factor of 0.75 and the losses are 100watts

 

[Andy™]

so how would it be ifa transformer has a rated power of 1kva and a power factor of 0.75 and the losses are 100watts

use my working above and change values for your new question - do this and someone will tell you if you got it right

 

[capemoff]

ok i think ive got it know many thanks again

 

[Andy™]

ok i think ive got it know many thanks again

what answer did you get?

 

[capemoff]

99.86% i hope

 

[Andy™]

99.86% i hope

nope.

show your working so i can see where you went wrong

 

[capemoff]

original

1x.75=0.75

.10-0.75=0.65

so 65/75x 100= 86.6

 

[Andy™]

original 1x.75=0.75

.10-0.75=0.65

so 65/75x 100= 86.6

correct

 

[Andy™]

and now that you know how to work that out.... itll be of no use to you until a few years time when someone else asks this on a forum and you help them

 

[capemoff]

you are a absolute star many thanks for your help

 

[SPECIAL LOCATION]

and now that you know how to work that out.... itll be of no use to you until a few years time when someone else asks this on a forum and you help them

oh yeh of little faith....

he may use it in an exam? :^O:^O

 

[SPECIAL LOCATION]

you are a absolute star many thanks for your help

Hi capemoff...

welcome to the forum mateGuiness DrinkGuiness DrinkGuiness Drink

as you have found out....

there's good help on ere!!!Applaud Smiley

so doe be afraid to come back and ask more!!!

 

[Andy™]

oh yeh of little faith....he may use it in an exam? :^O:^O

OK then... after his exams, he will most likely have no use until a few years.....

 

[searley]

tried working this out from andyc answer above but getting no where the 600W is throwing me could somebody please show me how to work this question out.

a transformer has an output of 12kva & a power factor of 0.9 the total losses in the transformer are 600w = what is the efficiency of the transformer = 94.4% answer

done the 12x0.9 = 10.8 this is where i get lost off with the 600w

thanks for looking.

 

[Jono Pashley]

output/(output+losses)x100 = Transformer Efficiency.

Closest answer i got was 94.73%

with (12000 x 0.9)/((12000 x 0.9)+600)x100

 

[sparktobe]

tried working this out from andyc answer above but getting no where the 600W is throwing me could somebody please show me how to work this question out.a transformer has an output of 12kva & a power factor of 0.9 the total losses in the transformer are 600w = what is the efficiency of the transformer = 94.4% answer

done the 12x0.9 = 10.8 this is where i get lost off with the 600w

thanks for looking.

i first did the same calculation as yourself then re read the question :z :z

12kva output has to be transposed to kw to calculate 600w loss. i think. Guiness Drink

so is the transfomer rated at 12.6kva

 

[searley]

the answer is 94.4% but can`t get the calcs to add up.