1:2 Turn Ratio for 110:220? The Turn Ratio is Same, Shall its Rating be Same?
A step up transformer which has 110/220 turns. Can we replace it with 10/20 turns or 1:2? Turns ratio is same, shall its rating be same? Give appropriate reasons?
No. Because we know that flux is directly proportional to the ampere turns (Φ ∝ At). So if we reduce the number of turns i.e. turns ratio, flux will be also reduced which leads to reduce the induced EMF because EMF is directly proportional to the flux (EMF ∝ Φ). If we go about the transformation formula, the calculated value may be right but if we use the EMF equation of the transformer, it shows a different story. Let’s see what happens when we reduce the number of turns in the transformer windings.
Transformer Rating & Parameters
- N1 = 110 Turns
- N2 = 220 Turns
- E1 = 220V
- Flux = Φm = 9.01 mW (mille Weber)
- E2 = ?
When Turn Ratio is 110/220
To find E2, we know that
E2/E1 = N2/N1
E2 = (N2/N1) x E1
Putting the values
E2 = (220/110) x 220V
E2 = 440V
When Turn Ratio is 10/20
Now, if we use 10/20 Turns ratio instead of 110/220.
E2 = (N2/N1) x V1
E2 = (20/10) x 220V
E2 = 440V
We can see that the value of step up voltage is same in both case whether we use 10/20 or 110/220 turns.
But I’m lying. It’s not true.
Let’s turn around to the EMF equation of the transformer.
E1 = 4.44 x f x N1 Φm ……….. (Primary)
E2 = 4.44 x f N2 Φm ……….(Secondary)
In case of turn ratio of 110/220
E1 = 4.44 x 50 x 110 x 9.01 mW
E1 = 220V
E2 = 4.44 x 50 x 220 x 9.01 mW
E2 = 440V
In case of turn ratio of 10/20
E1 = 4.44 x 50 x 10 x 9.01 mW
E1 = 20V
E2 = 4.44 x 50 x 20 x 9.01 mW
E2 = 40V
Hmm. That is a huge different. That’s why we can’t use 10/20 turns ratio instead of 110/220 because flux is directly proportional to the ampere turns (Φ ∝ At). If we reduce the number of turns (turns ratio of the transformer), the amount of produced flux will be reduced because of lower ampere turns which causes to reduce the amount of inducted EMF too i.e. induced EMF is directly proportional to the flux (Φ ∝ EMF).
In short, If we reduce the turn ratio of a transformer from 110/220 to 10/20 or 1:2, The following may occurs.
- The current in the primary winding of the transformer may increase due to reduced amount of impedance (Z) and resistance (R) i.e. low turns means low inductive reactance (XL) where XL dependents on the inductance of the turns.
- There may be high power loss due to high current in the primary as well as high power loss (I2R) which may leads to burn the primary windings of the transform.
- The induced EMF will be reduces as well due to low magnetic flux which depends on the number of coil turns.
Related Post: Why Transformer Rated In kVA, Not in KW?
Good to Know
- Transformer ratio of 2:1 is not the same as 1:2.
- Transformer turn ratio of 2:1 means this is a step down transformer.
- similarly, turn ratio of 1:2 shows a step up transformer.
- Turn ratio of 2:1 indicate that there are two turns in the transformer primary for the single turn in the secondary winding.
- In addition, turn ratio of 1:2 shows that if there are 1V in the primary, the voltage in the secondary would be 2V.
- Flux is directly proportional to the Ampere-Turns (At), not proportional to the turns ratio (N).
- In a 2:1 transformer ratio, if the current in the primary is 2A and 1A in the secondary, we are having 2 ampere turns (At) in the primary and 1 At in the secondary.
- Flux in the Primary and Secondary Winding of a transformer is always same.
- Transformer does not change the value of power, frequency, flux but only and only step up or step down the level of AC voltage or current (i.e. transformer won’t operate on DC).
- In short, if we reduce the number of turns (i.e. replacing 110/220 with 10/20), there will be insufficient flux in the core of transformer which will not work according to the rated parameters and design.
- Related Posts:
- How Find the Rating of Transformer in kVA (Single Phase and Three Phase)?
- Transformer Phasing: The Dot Notation and Dot Convention
- Transformer Efficiency, All day Efficiency & Maximum Efficiency
- TRANSFORMER NAMEPLATE (GENERAL REQUIREMENTS).
- In a Capacitive Circuit, Why the Current Increases When Frequency Increases?
- In an Inductive Circuit, Why the Current Increases When Frequency Decreases?
- Why Power Factor Decreases When Inductance or Inductive Reactance Increases?
- Why Power Factor Decreases When Capacitive Reactance Increases or Capacitance Decreases?