Abstract
A comprehensive comparison of the dynamic and steady state performance
characteristics of permanent magnet synchronous motors (PMSM) with
interior and surface rotor magnets for line-start operation is presented.
The dynamic model equations of the PMSM, with damper windings, are
utilized for dynamic studies. Two typical loading scenarios are examined:
step and ramp loading. The interior permanent magnet synchronous motor
(IPMSM) showed superior asynchronous performance under no load, attaining
faster synchronism compared to the surface permanent magnet synchronous
motor (SPMSM). With step load of 10 Nm at 2 s the combined effect of the
excitation and the reluctance torque forced the IPMSM to pull into
synchronism faster than the SPMSM which lacks saliency. The ability of the
motors to withstand gradual load increase, in the synchronous mode, was
examined using ramp loading starting from zero at 2 s. SPMSM lost
synchronism at 12 s under 11 Nm load while the IPMSM sustained synchronism
until 41 seconds under 40 Nm load. This clearly suggests that the IPMSM
has superior load-withstand capability. The superiority is further
buttressed with the steady state torque analysis where airgap torque in
IPMSM is enhanced by the reluctance torque within 90E to 180E torque angle.
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