The tap changer

The converter transformers (rectifier and inverter) can be equipped with a tap changer.

Demand to Change Taps

The tap changer controller generates the Up or Down order sent to the tap changer of the converter transformer in order to maintain α or γ angle in the range set by:

If the angle is not within the range, an up or down request is generated and sent to the tap changer in order to bring the angle back within the range ( if the tap has not yet reached any of the limits). The size of the range must be selected to avoid hunting (i.e. oscillation of the angle between the  Up area and the Down area). Usually:

• Range=at least 1.5 x maximum variation of angle corresponding to a tap

The default range values (adjustable) are shown in the following table:

Typical angles limiting the range.