The skin-eﬀect coeﬃcient k1R for hollow conductors is given, for example, in 
If msl = 1 and γ = 0, the skin-eﬀect coeﬃcient k1R = ϕ1(ξ1) (as for a cage winding).
If γ = 0 the currents in all conductors are equal and
k1R ≈ ϕ1(ξ1) + m 2 sl − 1 3
Eqn (B.10) can also be used for calculation of additional winding losses in large d.c. commutator motors.