Question

What is the function of equalizer ring ?
1. To achieve unequal distribution of current at the brushes thereby helping to get sparkless commutation
2. To avoid equal distribution of current at the brushes thereby helping to get sparkless commutation
3. To avoid unequal distribution of current at the brushes thereby helping to get sparkless commutation
4. To achieve equal distribution of voltage at the poles thereby helping to get sparkless commutation

Answer 1

Correct Answer - Option 3 : To avoid unequal distribution of current at the brushes thereby helping to get sparkless commutation

• All the Conductors lay in any parallel path under one pair of poles in the lap winding.
• If the flux from all the poles is exactly the same, the induced emf and hence current carried by each path will be equal in the ideal condition.
• There is always a slight unbalance of emf in the various parallel paths due to either variation in air gap length or different in magnetic properties of poles material.
• As a result conductors under stronger poles generate greater emf and hence carry larger current than remaining conductors.
• Due to this, the current distribution at the brushes becomes unequal. It means that some brushes are overloaded and carry more current than normal current while the remaining brushes carry less current due to underloaded.
• 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 avoid these conditions.