Closed and Open Windings

        Armature windings are classified into two different types namely i) Closed type winding ii) Open type winding.

1.1 Closed Type Winding

       In this type of winding, a closed path is formed around the armature. The starting point of the winding is reached again after passing through all the turns. The current passing through closed type of winding is through brushes placed on commutator. The commutator segments are connected to various armature coils.

       The armature current gets divided into different parallel paths. The current flowing through the coil changes continuously but from brush side the winding view remains same and polarity is maintained which is in effect due to use of commutator segments.

       The closed type of winding is normally used in a.c. and d.c. commutator machines. This type of winding is usually double layer.

1.2 Open Type Winding

       In case of a.c. machines, commutator is not used and hence closed winding is not required to be used. In such cases pen type winding is used. The armature is left open at one or more points.

       The ends of each section of the winding can be brought at the terminals to do the required type of interconnection externally. The open type of winding is preferred over closed type as it gives better flexibility in design and freedom of connections.

       These type of windings are either single layer type or double layer type and are mainly used in induction machines and synchronous machines.