relationship between rotor flux angle and Iq for IPM

   I read  SPRUHP4.pdf, and see "Ideal Orientation: 90 degrees for non-salient synchronous; slightly more for salient machines, and slightly less in asynchronous machines since part of the current vector is also used to produce rotor flux" on page 11. 

    So can you give me the relationship or formula between rotor flux angle and Iq for IPM?

    Best regards,

Qian.Miao