Bad commutation

Bad commutation

A machine is said to have poor or bad commutation if  there is sparking at the brushes and commutator surface . the bad commutation may be caused by mechanical or electrical  conditions. The mechanical conditions include uneven commutator  surface non uniform brush pressure, vibration of brushes in the brush holders etc. the electrical condition include an increase in voltage between the commutator segment , an increase in the current density at the trailing edge of the brush etc.