Question

Equalizer rings are required in case the armature is having _________ winding.
1. lap winding
2. wave winding
3. delta winding
4. duplex winding

Answer 1

Correct Answer - Option 1 : lap winding

• Equalizer rings are required in case the armature is having lap winding.
• In lap winding the numbers of parallel path are equal to the total of number poles and is used in low voltage and high current dc machines.
• Under ideal conditions, the flux from all the poles is exactly same, hence the induced emf and current carried by each path will be equal.
• But under practical operating condition, there are variations in air gap length or difference in magnetic properties of poles material which causes a slight unbalance of induced emf in the various parallel paths.
• As a result, conductors under stronger poles generate greater emf and hence carry larger current than remaining conductors.
• It means that some brushes are overloaded and carry more current than normal current while the remaining brushes carry less current due to under loaded.
• The current does not reverse completely in a given commutation time period due to overloaded brushes and that will cause sparking between brushes and commutator surface.
• The equalizer rings are used to overcome such problem.
• Hence, the function of equalizer rings is to avoid unequal current distribution at the brushes and to reduce sparking between brushes and commutator.
• The equalizer rings are low resistance copper conductor which connects those points in the armature winding which have potential difference between them. 
• If there are potential differences between such points, the circulating current flows through equalizer rings rather than brushes.
• Thus, the equalizer rings relieve the brushes to the circulating current by causing the latter to be passed by equalizer rings.