Understanding Transformer Turns Ratio: Basics and Measurement

This article explains the fundamentals of transformer turns ratio, providing the relevant equation and mentioning the transformer turns ratio meter used for testing.

A transformer is built using coils, referred to as the primary and secondary windings, which are not electrically connected. These coils are positioned closely together, either stacked on top of each other or placed side-by-side on an iron core.

The core function of a transformer is to convert alternating voltage from one level to another. Its operation is based on the principle of electromagnetic induction. Applying AC voltage to the primary winding creates a changing magnetic field, which then passes through the secondary windings. This induces voltage changes in the secondary winding. According to Lenz’s law, the output voltage will have the opposite polarity compared to the input voltage.

Setup for Transformer Turns Ratio Testing

Transformers are categorized into two main types: step-up and step-down, depending on the relationship between the input and output voltage values.

• A step-up transformer increases the voltage, meaning the output voltage is higher than the input voltage.
• A step-down transformer decreases the voltage, meaning the output voltage is lower than the input voltage.

Transformer Turns Ratio Equation

The equation for transformer turns ratio is expressed as follows:

Vs/Vp = Ns/Np

Where:

• Vs = Secondary AC voltage
• Vp = Primary AC voltage
• Ns = Number of turns on the secondary winding
• Np = Number of turns on the primary winding

Therefore:

Secondary AC voltage / Primary AC voltage = Turns on secondary / Turns on primary

Transformer Turns Ratio Meter

Transformer Turns Ratio Meter

In transformer terminology, ‘H’ typically denotes high voltage windings, while ‘X’ signifies low voltage windings.

Figure 1 (shown above with alt text “Setup for Transformer Turns Ratio Testing”) illustrates a simple setup for testing transformer turns ratio. Figure 2 (shown above with alt text “Transformer Turns Ratio Meter”) depicts a transformer turns ratio meter from Veer Electronics.

The Veer Electronics transformer turns ratio meter offers the following features:

• Fully automatic operation.
• Ratio range: 0.8 to 200, with 5 digits of resolution for display.
• Measurement accuracy: +/- 0.1% for both voltage and ratio measurements.
• Excitation voltage/current: Up to 60V / Up to 500mA.
• Supports 3-Phase Connections.
• Memory to store 200 test samples.