Hence some modifications are necessary for satisfactory operation on ac. These modifications are

(i) Series field with as few turns as possible in order to reduce reactance.
(ii) Large number of armature conductors to compensate for reduced field and develop a given torque
(iii) Compensating winding is provided to neutralize the armature reaction effect
(iv) Large number of poles with lesser flux per pole in order to lower transformer emf in the short-circuited element of the armature winding
(v) Very small ari gap due to weak field
(vi) Laminated all parts of magnetic circuits to reduce eddy current losses
(vii) Design for operation on low voltage and low frequency in order to give less inductance and so to improve operating characteristics and
(viii) Provision of commutating or inter poles in order to have good commutation, increased efficiency and also increased output with a given size of armature core.