15 September 2017

Equalization Ring or Equalization connection

  • 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 same, the induced elf and hence current carried by each path will be equal in the ideal condition. 
  • There is always a slight unbalance of elf in the various parallel paths due to either variations 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. 
  • The current distribution at the brushes becomes unequal due to above reason. 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 avoid such conditions. Therefore 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. 
  • The brushes relieves from excessive loading by passing circulating current through the equalizing rings.

Example
  • Let us consider 4 – poles, 12 – coils simplex lap winding of DC Generator. One Equalizer ring is connected to coil sides which are two pole pitch a part in this case.
  • Number of connections to one equalization ring is equal to the pair of poles = 2
  • Maximum numbers of equalization rings
              = Number of coil sides / Number of pair of poles                                                         = 24 / 2
              = 12
  • However the number of equalizer rings is not greater than 20 in higher rating machines.
Is it necessary to connect equalizer rings in simplex wave winding? Why?
  • No, if the magnetic properties under different poles are not uniform, all the armature conductors are distributed over all the poles in the wave winding. Therefore all the parallel paths are equally affected by the magnetic circuit.
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