Use of Transformers

• The Turns Ratio ($n$) is the ratio of the number of turns in the secondary coil ($N_s$) to the number of turns in the primary coil ($N_p$).

• According to the Transformer Equation, the ratio of secondary voltage ($V_s$) to primary voltage ($V_p$) is directly proportional to the turns ratio: $\frac{V_s}{V_p} = \frac{N_s}{N_p}$

• In an Ideal Transformer, power is conserved ($P_{in} = P_{out}$), meaning the product of voltage and current remains constant: $V_p I_p = V_s I_s$.

• This implies that if voltage is stepped up, the current must be stepped down proportionally: $\frac{I_s}{I_p} = \frac{N_p}{N_s}$

Step-Up Transformation

• Application: Used at power plants to increase voltage for long-distance transmission.
• Mechanism: $N_s > N_p$, resulting in $V_s > V_p$. This reduces current, which significantly lowers energy loss due to resistance in wires ($P_{loss} = I^2 R$).

Step-Down Transformation

• Application: Used at substations and in electronic devices to reduce high transmission voltages to safe, usable levels (e.g., 120V or 240V for homes).
• Mechanism: $N_p > N_s$, resulting in $V_p > V_s$. This increases the available current for consumer use.

• Ideal vs. Real Transformers: While ideal transformers assume 100% efficiency, real transformers experience losses through Eddy Currents (circulating currents in the core), Hysteresis (magnetic friction), and Copper Losses (resistance in the windings).

• Check the Input Type: Always verify if the input is AC. Transformers do not work with steady DC because DC does not create the changing magnetic flux required for induction.

• Power Conservation: In problems involving ideal transformers, use $P_p = P_s$ to find missing current or voltage values before applying the turns ratio formula.

• Unit Consistency: Ensure all voltages are in the same units (e.g., kV vs V) before calculating ratios to avoid decimal errors.

• Sanity Check: If a transformer is 'Step-Up', your calculated $V_s$ must be greater than $V_p$. If it is not, re-check your ratio orientation ($N_s/N_p$ vs $N_p/N_s$).