Explanation: fr is called the rotational or speed frequency, since its value depends upon the relative velocity between the flux density wave and the armature coil. 4. In AC rotating machines, the generated or speed EMF
A. leads Φ by 90°
B. lags Φ by 90°
C. is in phase with working flux
D. lags Φ by 180°
Answer:A
Explanation: fr is called the rotational or speed frequency, since its value depends upon the relative velocity between the flux density wave and the armature coil. 4. In AC rotating machines, the generated or speed EMF
A. leads Φ by 90° B. lags Φ by 90° C. is in phase with working flux D. lags Φ by 180°
Explanation: e = Emaxcos(ωrt-π/2)