In a 4:1 step up transformer, what would give a reflected impedance of 1 kOhm?
- 1 kOhm.
- 16 kOhm.
- 4 kOhm.
Explanation
Reflected (primary) impedance equals the load times the square of the primary-to-secondary turns ratio. For a 4:1 step-up, Np/Ns = 1/4, so Zp = ZL x (1/4)-squared = ZL/16. To make Zp equal 1 kOhm, the load must be 16 x 1000 = 16 kOhm. Forgetting to square the ratio would mistakenly give 4 kOhm.
luca92 asking:
why??
Community Comments (2)
T
trap2307 Posts: 43 16.04.2013 / 17:30
Hello!
Zp=Zs*(Np/Ns)^2 = 1*(4/1)^2=16
http://en.wikipedia.org/wiki/Transformer
http://upload.wikimedia.org/math/f/4/3/f4390640de234f03046a25667498b917.png
Zp=Zs*(Np/Ns)^2 = 1*(4/1)^2=16
http://en.wikipedia.org/wiki/Transformer
http://upload.wikimedia.org/math/f/4/3/f4390640de234f03046a25667498b917.png
P
Ptarbin Posts: 3 19.05.2016 / 22:53
If it's a 4:1 step UP transformer, wouldn't Np = 1 and Ns = 4?
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