calc formulas needed

[searley]

could any body help with these ?

a transformer is rated at 10kw but is only delivering 9.8kw.copper losses are 0.33kw and iron losses are 0.2kw. calc the efficiency of the transformer.

a transformer has 400 turns (pri) and 200v(pri) it produces 100v(sec) with load=10ohms. calc current(pri)

determine the resistance of 100m of aluminium conductor.csa is 120mm.use the resistivity of aluminium =2.84x10-8ohms

a 10 microfarad capacitor is connected to a 240v 50hz supply.calc the capacitive reactance ?

calculate the total resistance (rounded up value) from the following information - 100 copper cable,1.5sqmm with a resistivity of 17.5x10-9ohms

will this keep you`s going for now. just going to the fridge for a beer !!!!!! :Y :Y

 

[Apache]

could any body help with these ?a transformer is rated at 10kw but is only delivering 9.8kw.copper losses are 0.33kw and iron losses are 0.2kw. calc the efficiency of the transformer.

98% and from info supplied it's iron!

a transformer has 400 turns (pri) and 200v(pri) it produces 100v(sec) with load=10ohms. calc current(pri)

100V * 10 ohms = 1000W

1000W / 200V = 5ohm primary

determine the resistance of 100m of aluminium conductor.csa is 120mm.use the resistivity of aluminium =2.84x10-8ohms

a 10 microfarad capacitor is connected to a 240v 50hz supply.calc the capacitive reactance ?

calculate the total resistance (rounded up value) from the following information - 100 copper cable,1.5sqmm with a resistivity of 17.5x10-9ohms

will this keep you`s going for now. just going to the fridge for a beer !!!!!! :Y :Y

Dont have a calc handy and hate the windows scientific calc for the others

 

[Jono Pashley]

Transformer Efficency is (Output / (Output+Losses)) x 100

so.

Efficency = 9800/(9800+330+200) x100 = 94.86%

Capacative Reactance = 1/(2 x pi x f x c)

1/(2 x 3.14 x 50 x 10uF) = 318.3ohm

Resistivity = pl/a

p=resistivity

l=length

a=area

 

[Apache]

Transformer Efficency is (Output / (Output+Losses)) x 100so.

Efficency = 94.86%

wouldn't efficiency = output/input * 100

 

[Jono Pashley]

Transformer use a different Efficiency Calc

 

[searley]

the answer on the sheet is 90.4% think i got it .

9.8

----- x100 =90.489

10.83

:Y :Y:Y:Y

 

[Jono Pashley]

the answer on the sheet is 90.4% think i got it .9.8

----- x100 =90.489

10.83

:Y :Y:Y:Y

Where are you getting 10.83KW from...

10kw is the rating not its output the copper losses stated are for 9.8kw.

even is you added the losses to 10kw you only get 10.53kw.

 

[searley]

10.83 came up with the answer when i checked on the web site the question was on.

when i look again i can see where you are coming from.

 

[msb2003]

machine efficiency is output / input but transformers have to power the losses as well as the output so they use output / (output + losses)

other questions above

1. determine the resistance of 100m of aluminium conductor.csa is 120mm.use the resistivity of aluminium =2.84x10-8

2. calculate the total resistance (rounded up value) from the following information - 100m copper cable,1.5sqmm with a resistivity of 17.5x10-9

1. Resistance = (2.84x10-8 x 100) / 120x10-6 (convert square mm to square m)

= 0.0236 ohms

2. Resistance = (17.5x10-9 x 100) / 1.5x10-6

= 1.166 ohms