hey people sorry big revison day... maybe a few questions.. thanks

[robinson]

hey everyone big revison day so was wonderin if anyone could help me with a few questions very much appriciated... cause tbh this websites better than college lol..

17 http://www.swindon-massive.co.uk/electrical/revision/2360pt1/2330_lev2hotpot_unit2/trannycalc.JPG If the circuit here has 10A secondary through R, 60 turns N1 and 300 turns N2, what is the I1 primary current ?

10A

5.5A

0.5A

50A

 

[PoorFish]

Greetings

From what I understand you have to use the formula

Vs/Vp=Ns/Np=Ip/Is

therefore

300/60 = Ip/10

so

300 x 10 / 60 = 50 a

 

[robinson]

cheers mate

 

[kme]

Okay - correct answer; but maybe an easier way of remembering:

The voltage/current through a TX is proportionate to the coil winding ratio; excluding losses.

So the TX has a 60:300 turn ratio, which boils down to a 1:5. Okay so far?

Because there are more turns to the secondary, the voltage will be stepped up; therefore the current MUST be stepped down (P=VI).

So if the secondary has xAmps, at y voltage, then the primary must have:

Voltage: y multiplied by 1/5.

Current: x divided by 1/5 (or multiplied by 5/1)

so, from the example, 10A sec. multiplied by (5/1.....=5) = 50A

Make life easier, and boil the ratio down as far as possible.

KME

 

[robinson]

woahh that is good mate thank you! dont know why colleges dont put the easy ways everyone comes up with on here??

 

[robinson]

does anyone have a good picture representing the power distribution???

i have one in a book which i have but its not amazing and cant find a good one online??

 

[robinson]

its ok thanks i got the pic now does anyone know a nice way to explain power factor including the formulae??

 

[PoorFish]

one way is

pf = KW/KVA