1 Name two methods that can be used to minimise the effect of hunting in a synchronous motor. 5.2 Define distribution factor. 5.3 Calculate the terminal EMF on open circuit.

You're on a roll — Here are the solutions to Question 5. 5.1 Name two methods that can be used to minimise the effect of hunting in a synchronous motor. • Using damper windings (or amortisseur windings) in the rotor pole faces. • Using a flywheel to increase the moment of inertia of the rotor. 5.2 Define the term distribution factor. The distribution factor (k_d) is a factor that accounts for the reduction in the induced electromotive force (EMF) in an alternator winding due to the coils being distributed in several slots per pole per phase, rather than being concentrated in a single slot. It is always less than or equal to one. 5.3 Calculate the terminal EMF on open circuit. Given: Number of poles P = 4 Frequency f = 50 Hz Number of phases m = 3 Number of slots S = 38 Conductors per slot Z_s = 18 Flux per pole = 0.04 Wb Winding type: Single-layer Connection: Mesh-connected (Delta) Step 1: Calculate the number of slots per pole (S_p) and slots per pole per phase (q). S_p = (S)/(P) = (38)/(4) = 9.5 q = (S_p)/(m) = (9.5)/(3) = 3.1667 Step 2: Calculate the electrical angle per slot (). = (360^)/(S) × (P)/(2) = (360^)/(38) × (4)/(2) = (360^)/(38) × 2 = 18.947^ Step 3: Calculate the distribution factor (k_d). k_d = ((q)/(2))q(()/(2)) k_d = ((3.1667 × 18.947^)/(2))3.1667 ((18.947^)/(2)) k_d = ((30^))/(3.1667 (9.4735^)) k_d = (0.5)/(3.1667 × 0.16458) = (0.5)/(0.5209) = 0.9598 Step 4: Calculate the number of turns per phase (N_ph). Total conductors Z_total = S × Z_s = 38 × 18 = 684. Conductors per phase Z_ph = Z_totalm = (684)/(3) = 228. For a single-layer winding, N_ph = Z_ph2 = (228)/(2) = 114 turns. Step 5: Calculate the EMF per phase (E_ph). Assuming a full-pitch winding, the pitch factor k_p = 1. The formula for induced EMF per phase is E_ph = 4.44 k_p k_d f N_ph.