The rotor of 3-phase slip ring induction motor is fed from a 3-phase supply with its stator winding short circuited having rotor rotating clockwise at a speed of Nr, then the _________

• A. speed of air gap field w.r.t. stator is Ns-Nr anticlockwise
• B. speed of air gap field w.r.t. stator is Ns-Nr clockwise
• C. speed of airgap field w.r.t rotor is Ns clockwise
• D. speed of airgap field w.r.t. stator is Ns-Nr clockwise