N₁/N₂ = V₁/V₂
I₁/I₂ = N₂/N₁ = V₂/V₁
N₁ = Primary turns
N₂ = Secondary turns
V₁ = Primary voltage
V₂ = Secondary voltage
I₁ = Primary current
I₂ = Secondary current
Step-Up: Power transmission (11kV → 400kV), CRT displays
Step-Down: Phone chargers (230V → 5V), laptop adapters
Isolation: Medical equipment, safety barriers
The transformer turns ratio is the relationship between the number of turns in the primary winding (N₁) and the secondary winding (N₂) of a transformer. This ratio directly determines how the voltage and current are transformed between the primary and secondary sides. In an ideal transformer, the voltage ratio equals the turns ratio: V₁/V₂ = N₁/N₂.
The turns ratio is fundamental to transformer design and is used to step up or step down voltages for various applications, from power transmission lines that use high voltages for efficient long-distance transmission, to household devices that require low voltages for safe operation.
In an ideal transformer, power is conserved between the primary and secondary windings: P₁ = P₂, which means V₁ × I₁ = V₂ × I₂. This leads to an important relationship: as voltage increases (step-up), current decreases proportionally, and vice versa (step-down).
This principle is why high-voltage transmission is used for power distribution. By stepping up the voltage, the current is reduced, which minimizes power losses in the transmission lines (since losses are proportional to I²R). At the destination, step-down transformers reduce the voltage to safe levels for consumer use.
Transformer turns ratio calculations are based on ideal assumptions. Actual transformer performance may vary due to winding resistance, leakage inductance, core losses, and load conditions. Real transformers have efficiencies typically between 95-99%. Consult datasheets or an electrical engineer for precise design and safety-critical applications.