Tuesday, 24 January 2017

Transformer Calculations

 (a) Output p.d. = (secondary turns/primary turns)
× input p.d. 1
= (720/80) × 36 1
= 324V. 1
(b) Output p.d. = (secondary turns/primary turns)
× input p.d. 1
= (80/720) × 36 1
= 4V. 1
Total 6
3
coil A coil B power supply output mark
(V) (V)
9200 800 230 20 1
11500 250 230 5 1
9600 1000 24 2.5 1
2000 32000 25000 400000 1
Total 4


  1. A step down transformer reduces voltage from 240 V (Vin) to 6 V.  If there are 1000 turns on the primary windings (Np),  how many are there on the secondary windings ?
Vout = Ns            6V/240V = Ns/1000   Ns/1000 = 0.025            Ns = 1000 x 0.025 = 25 turns
 Vin         Np


  1. A step down transformer reduces voltage from 240 V (Vin) to 12 V (Vout).  If Np = 200 turns calculate  Ns.

Vout = Ns     12V/240v = Ns/200 Ns = 12/240 x 200 = 10 turns
Vin         Np



  1. A transformer has 1000 turns on it’s primary windings and 100 in the secondary . If Vin is in 20V calculate Vout.

Vout = Ns     V out/20v = 100/1000  Vout= 20 (100/1000) = 2 V
Vin         Np

4.  In a transformer Np = 2000 turns and Ns = 50 turns.  If Vin =400 V, calculate Vout.
Vout = Ns     V out/400v = 50/2000  Vout= 400 (50/2000) = 10 V
Vin         Np

5.  A step up transformer increases voltage from 4 V to 40 V.  If Np = 100 turns calculate Ns.
Vout = Ns     40V/4v = Ns/100 Ns = 40/4 x 100 = 1000 turns
Vin         Np

6.  A step down transformer reduces voltage from 100 V to 10 V.  If Np = 2000 turns calculate Ns.
Vout = Ns     10V/100v = Ns/2000 Ns = 10/100 x 2000= 200 turns
Vin         Np

7.  In a transformer Ns = 10 turns and Np = 500 turns.  If Vout = 10 V calculate Vin.
            Vin/Vout = Np/Ns rearranging Vin = VoutNp/Ns  Vin = 10(500/10) = 500V

8.  If Ns = 40 turns and Np = 4000 turns calculate Vin if Vout = 10 V.

Vin/Vout = Np/Ns rearranging Vin = VoutNp/Ns  Vin = 10(4000/40) = 1000V


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