A transformer has 1200 turns primary and 4800 turns secondary. What value of load resistance would be required to give a reflected impedance of 1000 ohms?
- 4 kOhm.
- 1 kOhm.
- 16 kOhm.
Explanation from PART66Online
Reflected impedance equals the load times the square of the turns ratio (Np/Ns). Here Np/Ns = 1200/4800 = 1/4, so Zp = ZL x (1/4)-squared = ZL/16. Setting that to 1000 ohms gives ZL = 16,000 ohms = 16 kOhm. Ignoring the squaring would wrongly give 4 kOhm.
B
Benny asked · 30 Apr 2012
How to do it?
Community Comments (5)
O
ome
3 May 2012
the formula?
M
MridulDev
18 Jun 2012
N2/N1=(Z2/Z1)^1/2
ie, turns ratio equals root under impedance ratio.
ie, turns ratio equals root under impedance ratio.
J
joselizardo
24 Feb 2015
4800/1200= 4
Z2=1000
4=(1000/Z1)^1/2
4^2 =1000/Z1
Z1=1000/16 = 62.5
WHY 16KOhm?
Z2=1000
4=(1000/Z1)^1/2
4^2 =1000/Z1
Z1=1000/16 = 62.5
WHY 16KOhm?
A
Alekrg
18 Apr 2017
You just inverted Z1 and Z2. You are requested to calculate Z2.
J
JD2016
19 Apr 2017
N2 =4800
N1 = 1200
Turns Ratio N2/N1 = 4.
Ratio of impedances is the same as the Turns Ratio SQUARED.
Z1 = 1000
Z2 =?
Z2/Z1 = (N2/N1)**2
Z2 = Z1 (N2/N1)**2
= 1000 (4)**2
= 1000 x 16
= 16,000
= 16 Kilohms
N1 = 1200
Turns Ratio N2/N1 = 4.
Ratio of impedances is the same as the Turns Ratio SQUARED.
Z1 = 1000
Z2 =?
Z2/Z1 = (N2/N1)**2
Z2 = Z1 (N2/N1)**2
= 1000 (4)**2
= 1000 x 16
= 16,000
= 16 Kilohms
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