2. a) b) Explain why Permanent Magnet AC machines with surface mounted magnets are referred to as non-salient, whilst those with buried magnets are referred to as salient. [4] A 3-phase 6-pole buried magnet PMSM has a saliency ratio of L/Ls = 3. The d-axis inductance Ld is 5mH. The back-emf per phase of the machine is 240V at a base speed of 3000rpm. The rated phase current is 30A. i. Determine the rated excitation frequency in electrical rad/s. [2] ii. Determine the advance angle y that results in maximum torque that this machine can achieve with rated current. Hence calculate the respective values of the d- and q-axis currents under this condition and determine the maximum torque. [8] iii. Neglecting stator resistance, draw neatly the phasor diagram for the case when the machine is drawing maximum torque at a speed of 1500rpm. [6] 2. a) b) Explain why Permanent Magnet AC machines with surface mounted magnets are referred to as non-salient, whilst those with buried magnets are referred to as salient. [4] A 3-phase 6-pole buried magnet PMSM has a saliency ratio of L/Ls = 3. The d-axis inductance Ld is 5mH. The back-emf per phase of the machine is 240V at a base speed of 3000rpm. The rated phase current is 30A. i. Determine the rated excitation frequency in electrical rad/s. [2] ii. Determine the advance angle y that results in maximum torque that this machine can achieve with rated current. Hence calculate the respective values of the d- and q-axis currents under this condition and determine the maximum torque. [8] iii. Neglecting stator resistance, draw neatly the phasor diagram for the case when the machine is drawing maximum torque at a speed of 1500rpm. [6]