Transformer Turns Ratio Calculator NZ
This calculator works out a transformer's turns ratio and the secondary voltage it produces, from the number of turns on each winding and the primary voltage. A transformer changes an alternating voltage from one level to another using two coils wound on a shared magnetic core. The ratio of the number of turns on the secondary coil to the primary coil sets how the voltage changes: more turns on the secondary steps the voltage up, fewer steps it down, in direct proportion. The same ratio works in reverse for current, since a transformer roughly conserves power, so stepping the voltage up steps the current down and vice versa. Transformers are everywhere in the electrical world, from the power grid that steps voltage up for transmission and down for homes, to the small adapters that power electronics. This tool computes the key figures. You enter the primary turns, the secondary turns, and the primary voltage, and the calculator returns the secondary voltage, the turns ratio, whether the transformer steps up or down, and the current ratio. The results update as you type, so you can design or analyse a transformer quickly. Use it for electronics and physics study, for understanding power distribution, or for working with transformers and adapters. The secondary voltage is the primary voltage times the secondary turns divided by the primary turns, and the turns ratio is simply that ratio of turns. A ratio greater than one means a step-up transformer, raising the voltage; less than one means step-down, lowering it. The current ratio is the inverse of the voltage ratio, reflecting the conservation of power in an ideal transformer, so a step-down transformer that halves the voltage roughly doubles the available current. Real transformers have small losses, so actual figures are a little below these ideal values.
Vs = Vp x Ns / Np. Turns ratio = Ns / Np. Ratio above 1 steps up; below 1 steps down. Current ratio is the inverse, since power is conserved. Ideal transformer.
How it works
The secondary voltage is the primary voltage multiplied by the ratio of secondary turns to primary turns. That same ratio is the turns ratio: above one it steps the voltage up, below one it steps it down. Because an ideal transformer conserves power, the current changes by the inverse ratio, so the secondary current ratio is the primary turns over the secondary turns.
Worked example
A transformer with 240 primary turns and 24 secondary turns has a turns ratio of 24 over 240, which is 0.1, a step-down transformer. From a 230 volt primary, the secondary voltage is 230 times 0.1, which is 23 volts. The current ratio is the inverse, 10, so the secondary can supply ten times the primary current.
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