# What is meant by HV and LV windings of transformer ?

The terms HV (High Voltage) and LV (Low Voltage) refer to the different voltage levels in a transformer’s windings, which are essential for stepping up or stepping down electrical voltage levels as required by the application.

HV windings in a transformer are the windings designed to handle higher voltage levels. These windings are typically connected to the higher voltage side of the transformer, such as the primary winding in a step-up transformer or the secondary winding in a step-down transformer. HV windings are constructed with more turns of thinner wire to withstand higher voltages while maintaining the desired current capacity and magnetic flux within the transformer’s design limits.

Conversely, LV windings are the windings designed to output or receive lower voltage levels relative to the HV windings. In a step-up transformer, LV windings would be on the secondary side, where the voltage is lower but the current is higher compared to the primary side. In a step-down transformer, the LV windings are on the primary side, receiving higher voltage but providing lower voltage to the secondary winding. LV windings are typically constructed with fewer turns of thicker wire to handle higher currents at lower voltages efficiently.

On a transformer nameplate or specification sheet, LV and HV are often used to denote the specific voltage ratings of the windings. LV indicates the lower voltage winding, while HV indicates the higher voltage winding. This labeling helps ensure proper installation and connection of transformers in electrical systems, as it clarifies which winding corresponds to which voltage level.

To find the HV and LV currents of a transformer, you need to refer to the transformer’s specifications or perform calculations based on the transformer’s turns ratio and the load connected to each winding. The current in each winding of a transformer is inversely proportional to its voltage, according to the transformer’s turns ratio (N1/N2 for a step-up transformer where N1 is the number of turns in the primary winding and N2 is the number of turns in the secondary winding). Specifically:

• For the HV winding: HV current (I_HV) = LV current (I_LV) × (N2 / N1)
• For the LV winding: LV current (I_LV) = HV current (I_HV) × (N1 / N2)

These formulas help determine the current in each winding based on the applied voltage and the transformer’s turns ratio. Actual current values also depend on the load connected to the transformer and its impedance, which influence the current drawn from each winding. Transformer ratings and specifications provide crucial information for designing and operating electrical systems effectively and safely.