Dual-Pole LSPM Motor with Dahlander Winding for High Inertia Loads

To improve the starting, the synchronization capability and the steady state performance of dual-pole synchronous motors, conventional stator winding arrangement with two separate sets of windings is being replaced with a single set of Dahlander type winding. This reduces the slot size, which ultimately contributes to a higher power density. Meanwhile, the use of single set of winding could effectively reduce the stator resistance, which limits the braking torque as well as the ohmic loss. For verification purposes, the performance characteristic of the dual-pole motor with these two winding structures are compared in terms of the starting and the synchronization capability. Finite Element (FE) simulation results confirm that the motor with Dahlander type winding exhibits a better synchronization capability, in particular, in case studies with higher load inertia.

I. Introduction

Inverter driven Induction Motors (IMs) are mainly adopted for applications where a wide and continuous range of operating speed is required. However, in many cases the cost of the drive unit itself could exceed the cost of the actual motor. Therefore, for two-speed applications such as desert coolers, the speed change is normally done through the pole-changing concept as opposed to the use of a drive unit. However, IMs normally operate at low power factor and efficiency duo to the motor slip. Line Start Permanent Magnet (LSPM) synchronous motor is another type of self-starting motor but with a higher efficiency, power factor, and power density [1]-[6]. The magnetic flux generated by the Permanent Magnets (PMs) gets locked in with the rotating three phase stator field, which eliminates the motor slip. Despite the advantages, the fixed polarity of the rotor poles had always prevented incorporating the pole-changing concept in LSPM motors.