powersys
Advanced Member level 1
d-axis q-axis
Copied from "Electric Machinery" by Fitzgerald (pg. 282, 6th edition):
Note that, by definition, the field winding produces flux which is oriented along the rotor d-axis. Thus, when phasor diagrams are drawn, the field-winding mmf and its corresponding flux are found along the rotor d-axis. The generated internal voltage is proportional to the time derivative of the field-winding flux, and thus it's phasor leads the flux by 90 deg. Since by convention the q-axis leads the d-axis by 90 deg, we see that the generated voltage phasor lies along the q-axis...
Questions
1) Which theory that motivated the author came to this comment: "...by convention, the q-axis leads the d-axis by 90 deg"? Why not the other way round?
2) The generated internal voltage is proportional to the time derivative of the field-winding flux, and thus it's phasor leads the flux by 90 deg. From mathematical point of view, how does the 'derivative' suggest that the voltage phasor leads the flux?
Thanks
Copied from "Electric Machinery" by Fitzgerald (pg. 282, 6th edition):
Note that, by definition, the field winding produces flux which is oriented along the rotor d-axis. Thus, when phasor diagrams are drawn, the field-winding mmf and its corresponding flux are found along the rotor d-axis. The generated internal voltage is proportional to the time derivative of the field-winding flux, and thus it's phasor leads the flux by 90 deg. Since by convention the q-axis leads the d-axis by 90 deg, we see that the generated voltage phasor lies along the q-axis...
Questions
1) Which theory that motivated the author came to this comment: "...by convention, the q-axis leads the d-axis by 90 deg"? Why not the other way round?
2) The generated internal voltage is proportional to the time derivative of the field-winding flux, and thus it's phasor leads the flux by 90 deg. From mathematical point of view, how does the 'derivative' suggest that the voltage phasor leads the flux?
Thanks