# Tap-Changing Transformer

Single-phase tap-changing transformer

**Library:**Simscape / Electrical / Passive / Transformers

## Description

The Tap-Changing Transformer block represents a single-phase tap-changing transformer. You can vary the turns-ratio of the transformer during the simulation using the control input.

Use this component to regulate or change the output voltage of a linear transformer during a simulation. To model the effects of saturation, consider using the Nonlinear Transformer block.

### Operating Principle

Use the control input **c** to change the tap position of the transformer.

Increase

**c**above the**Control threshold**,*t*, to increase the tap position*p*by one.Decrease

**c**below the negative of the**Control threshold**to decrease the tap position*p*by one.

This figure shows the tap-response to a control input.

In the diagram:

*N*is the nominal number of turns for the tap-changer winding._{0}*δ*is the percent change in turns per tap position step. Specify this value using the**Change per tap (%)**parameter.*p*and_{min}*p*are the minimum and maximum allowable tap indices. Specify these values with the_{max}**Minimum tap index (nominal=0)**and**Maximum tap index (nominal=0)**parameters.

To select the tap-changer winding, use the **Tap-changer
location** parameter. The overall turns ratio, *n*,
depends on this location:

`Primary`

$$n=\frac{{N}_{p}({N}_{0},\delta ,p)}{{N}_{s}}={n}_{0}\left(1+\frac{\delta p}{100}\right)$$

`Secondary`

$$n=\frac{{N}_{p}}{{N}_{s}({N}_{0},\delta ,p)}={n}_{0}{\left(1+\frac{\delta p}{100}\right)}^{-1}$$

where *n _{0}* is the nominal
turns ratio for the transformer.

### Equivalent Circuit

The equivalent circuit is shown in the diagram.

Here:

*R*and_{p}*R*are the primary and secondary series resistances, respectively. Changes in the tap position affect these values._{s}*L*and_{lp}*L*are the primary and secondary leakage inductances, respectively. Changes in the tap position affect these values._{ls}*R*and_{m}*M*are the magnetization resistance and inductance, respectively. Changes in the tap position affect these values.*n*is the turns ratio of the transformer.*G*and_{p}*G*are the primary and secondary leakage conductances, respectively. Changes in the tap position do not affect these values._{s}

## Ports

### Conserving

## Parameters

## Extended Capabilities

## See Also

Earthing Transformer | Ideal Transformer | Nonlinear Transformer | Three-Winding Transformer (Three-Phase) | Three-Winding Transformer (Three-Phase) | Two-Winding Transformer (Three-Phase) | Zigzag-Delta-Wye Transformer

**Introduced in R2018a**