Electrical Machines
To have sparkless commutation, the armature reaction effect in a DC machine is neutralized by

  compensating winding and commutating poles.
 increasing field excitation.
 fixing the brush axis inline with the pole axis.
 shifting the brush axis from GNA to MNA.

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Electrical Machines
Due to magnetic saturation, the flux per pole in a DC machine without brush shift

  decreases in both generators and the motors with load.
 increases in both the generators and the motors with load.
 increases in generators but decreases in motor with load.
 decreases in generators and increases in motor with load.

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