# Test and Measurement World

## Test and Measurement Electronics Equipments Section

One Stop For Your Test and Measurement Need

## Transformer turns ratio basics

This page describes transformer turns ratio basics with equation and mentions transformer turns ratio meter used for testing it.

Transformer is constructed by coils called primary ancd secondary which are not connected electrically. The coils are mounted close to each other either one on top of the other or side by side on iron core.

Transformer changes alternating voltage from one value to the other. It works on the principle of electromagnetic induction. AC applied to primary winding produces change in magnetic field passes through the secondary windings. This induces changes in voltage in the secondary. Output voltage will have also opposite polarity compare to input voltage due to lenz's law.

There are two types of transformer step up and step down based on input and output voltage values. If the output voltage is higher than input voltage, it is known as step up transformer. If the output voltage is lower than input voltage, it is known as step down transformer.

Equation for transformer turns ratio is expressed as follows:
Vs/Vp = Ns/Np
Secondary AC voltage/Primary AC voltage = Turns on secondary/Turns on primary

### Transformer turns ratio meter

In transformer 'H' is used for high voltage windings and 'X' is used for low voltage windings. Figure-1 depicts simple setup used for transformer turns ratio testing and figure-2 depicts transformer turns ratio meter from Veer Electronics.

Following are the features of this electronic equipment:
• Fully automatic
• Ratio Range: 0.8 to 200, 5 digits resolution for display
• Accuracy of measurement: +/- 0.1 % for voltage and ratio measurement
• Excitation voltage/current: upto 60V/upto 500mA
• 3-Phase Connections
• Memory to store 200 test samples