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Cars electrification – Simulation of the Toyota Prius IPMSynch motor using EMWorks2D

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Computer CAD design and simulation in profit of cars electrification 

Battery and electric motor are the main keys of any zero-gas emissions vehicle. Hence, engineers, researchers and labs are working to design and develop more reliable products that could meet any user requirements. In this application note, the Prius 2004 electric motor we analyzed using EMWorks2D. it is a 2D electromagnetic tool embedded inside SOLIDWORKS and provided by EMWorks. 

Figures below show 2D and 3D CAD models, created with SOLIDWORKS, of the 2004 Prius electric motor. Toyota Prius is among the earliest mass-produced hybrid car in the world. It came with an Interior permanent magnet synchronous motor (IPMSM). The Prius 2004 electric motor has the specifications data shown in table 1.

2004-Prius-IPMSM-a)-3D-CAD-model-b)-2D-CAD-model

Figure 1 - 2004 Prius IPMSM, a) 3D CAD model, b) 2D CAD model
 
Specifications Values
Rated Current 230A RMS
Rated Speed 1200RPM
Rated Torque 400Nm
Rated Power 50kW
Lamination Material M-19
Table 1 - Specifications of the 2004 PRIUS IPMSM [1] [2] [3]
 

The interior PM synchronous motor of Prius 2004 has 48 slots and 8 poles buried inside the rotor laminations core. Both rotor and stator cores are made of laminated steel M-19 (stacking factor is 0.94). This studied motor has 3 phase distributed windings, single layered with 9 turns per slot connected in series. Buried synchronous machine offers higher torque values compared to surface mounted machine. The torque is composed of two components: permanent magnet torque and reluctance torque. The V-shaped magnet housing is designed to increase the quadrature axis reactance, and this will help to obtain higher reluctance torque synchronized with PM torque. 

The following sections will show the different analyses performed using EMWorks products. 

No-Load Analysis

The rotor initial position is chosen as following: a north rotor pole axis (d-axis) is coincident with the phase AA’ axis. The cogging torque is the torque generated by the interaction between the ferromagnetic core and the permanent magnets. Prius IPMSM cogging torque results are shown in Figure 2. The no-load torque has a sin-wave shape with period of 7.5 deg (360 deg/48slots).  It reaches its peak of 1.79Nm at 2.5 deg. Figure 3 illustrates the magnetic flux density distribution at the position 0 deg when the windings excitation is zero. 

Cogging-torque-results

Figure 2 - Cogging torque results
 
No-load-magnetic-flux-density
Figure 3 - No-load magnetic flux density

Locked Rotor Analysis 

Measurement results realized by labs and published in [1] [2] [3], show the locked rotor torque results at different current rates. Figure 4 contains comparison of the torque results at different current values between EMWorks2D and measurement data. It shows that the peak torque can be reached around 60-68 deg (mechanical angle). Peak torque values versus current are plotted in Figure 5. 

Locked-rotor-torque

Figure 4 - Locked rotor torque
 
Motor-peak-torque-values-versus-the-motor-current-amplitude
Figure 5 - Motor peak torque values versus the motor current amplitude

Loaded Analysis 

The PM synchronous machine is supplied with sine wave excitation (230A RMS, 80Hz). The rotor speed is 1200 RPM. Figure 6 shows the magnetic flux density at 0 deg. High field spots are located near to the rotor magnets bridges. Animation of the magnetic field is shown in Figure 7. 

As mentioned above, in interior permanent magnet synchronous machine, the total torque is the sum of permanent magnet torque and reluctance torque. To have maximum total, a specific current angle should be determined. Figure 8 shows different torque types versus current angle. The total torque is maximum when the current angle is around 50 el. deg. The load torque results versus rotor angle are illustrated in Figure 9. it is oscillating between 434 Nm and 339 Nm. Hence, an average torque of 386.5 Nm is reached while the torque ripples are around 50 Nm. 

Flux-density-distribution-at-0-deg–windings-are-excited

Figure 6 - Flux density distribution at 0 deg – windings are excited


Magnetic-field-animation-versus-rotor-angle

Figure 7 - Magnetic field animation versus rotor angle
 
Different-torques-versus-current-angle
Figure 8 - Different torques versus current angle
 
Load-torque-versus-rotor-mechanical-angle
Figure 9 - Load torque versus rotor mechanical angle

Summary

During the past few years, the development of autonomous and efficient electric cars showed an important progress. The use of computer CAD design and simulation software has demonstrated its reliability to improvemajor componentsof an electric vehicle like the electric motors. EMWorks provides novel and easy to use products to help modeling and simulating electric motors inside SOLIDWORKS.
 

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