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No-Load and On-Load Analyses of a 24slot/ 8pole-Spoke Type Motor using EMWORKS2D inside SOLIDWORKS

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Electric motors are becoming increasingly used in industrial applications. They offer a high efficiency, high power factor and a wide speed range. The spoke type motor is one of the common electric motor types presented in the market today. 

Spoke type motors use a compact permanent magnets structure, arranged in spokes for a better torque generation [1]. With the adequate material selection, the spoke type motors have the highest torque density architecture among the permanent magnet motor types, provided they are cost-effectively manufactured and especially effectively cooled [1]. 

In this application note, the no-load and on-load analyses of the 24slot/8pole spoke type motor under study are computed using EMWORKS2D software inside SOLIDWORKS.  

Figure 1 illustrates a 2D model of the studied 24slot/ 8pole spoke motor designed using SOLIDWORKS.

 2D cross section of the 24slot/8pole Spoke Type Motor using SOLIDWORKS.

Figure 1 - 2D cross section of the 24slot/8pole Spoke Type Motor using SOLIDWORKS. 

Spoke Motor Settings 

1- Materials Selection

The materials selection of the spoke type motor directly affects the motor performance. It has been shown in [1] that the best material for the magnets is the neodymium iron boron, since they can be kept cooled. Table 1 illustrated the materials used for the spoke motor under study.

Motor component Material
Stator AISI 1010 Steel
Rotor AISI 1010 Steel
Magnets NdFeB: N4212
Table 1 - Selected materials for the spoke motor under study. 

2- Coercivity Direction for the Magnets

The coercivity directions of the spoke motor magnets is expressed in local cartesian coordinate systems.  The direction of the magnet magnetization can either be positive (case of north magnet) or negative (case of south magnet), as illustrated in figure 2.

Coercivity Direction of the Spoke Magnets

Figure 2 - Coercivity Direction of the Spoke Magnets. 

3- Defined Rotor Angle 

The rotor angle is defined in SOLIDWORKS as the angle between both the rotating rotor axis and the stationary axis of the stator, as shown in figure 3.

Rotor Angle Definition in SOLIDWORKS

Figure 3 - Rotor Angle Definition in SOLIDWORKS. 

4- Defined Winding Configuration

The spoke type motor under study is equipped with 24 double layer slots, presenting one parallel path and each phase is equipped with 30 turns.  

The 3-phase winding configuration of the spoke motor (A, B and C) is illustrated in the figure 4.

Winding configuration for the spoke motor

Figure 4 - Winding configuration for the spoke motor. 

Simulation and results 

1- No-Load analysis of the spoke type motor 

a- Cogging Torque of the Spoke Type Motor

The cogging torque of the spoke type motor is simulated for one period using EMWORKS2D inside SOLIDWORKS. The properties of the cogging torque study are listed in table 2. The cogging torque versus time curve is presented in figure 5.
 

Parameter Value
Start Simulation Time (s) 0
End Simulation Time (s) 0.03
Step Simulation Time (s) 0.001
Angular Velocity (deg/s) 500
Initial Angle (deg) 0
Table 2 -  Properties of the Cogging Torque Study. 
Cogging Torque versus time curve of the spoke type motor
Figure 5 - Cogging Torque versus time curve of the spoke type motor. 

b- No Load Analysis of the Spoke Type Motor 

The no load analysis of the spoke type motor is simulated for one period using EMWORKS2D inside SOLIDWORKS. Its properties are listed in table 3. The 3-phase winding linkage versus time curve is presented in figure 6, and the 3-phase induced voltage versus time curve is presented in figure 7.

Parameter Value
Frequency (Hz) 50
Start Simulation Time (s) 0
End Simulation Time (s) 0.02
Step Simulation Time (s) 0.00066667
Angular Velocity (deg/s) 4500
Initial Angle (deg) 0
Table 3 - Properties of the No Load Study. 
Flux Linkage versus time curve of the spoke type motor
Figure 6 - Flux Linkage versus time curve of the spoke type motor. 
Induced Voltage versus time of the spoke type motor
Figure 7 - Induced Voltage versus time of the spoke type motor. 

c- Magnetic field mappings of the Spoke Type Motor

The magnetic field mapping of the spoke type motor, one of the multiple no load analysis results, is viewed for an initial angular position of 0 degree, as presented in figure 8.

Magnetic Field Mapping of the spoke type motor under no load conditions, 0deg

Figure 8 - Magnetic Field Mapping of the spoke type motor under no load conditions, 0deg. 

2- On Load analysis of the spoke type motor

a- On Load Torque of the Spoke Type motor

The spoke type motor has been simulated under load conditions. The applied 3-phase sinusoidal current is given in equation (1), where the on-load study parameters are listed in table 4.

open curly brackets table attributes columnalign left end attributes row cell I subscript a equals space I subscript m a x space end subscript asterisk times space sin space left parenthesis 2 pi f asterisk times t i m e minus T subscript s h i f t end subscript right parenthesis end cell row cell I subscript a equals space I subscript m a x space end subscript asterisk times space sin space left parenthesis 2 pi f asterisk times t i m e minus fraction numerator 2 pi over denominator 3 end fraction minus T subscript s h i f t end subscript right parenthesis end cell row cell I subscript a equals space I subscript m a x space end subscript asterisk times space sin space left parenthesis 2 pi f asterisk times t i m e minus fraction numerator 4 pi over denominator 3 end fraction minus T subscript s h i f t end subscript right parenthesis end cell end table close

Parameter Value
Frequency, f (Hz) 50
Max Current,  I subscript m a x end subscript(A) 10
Time Shift,  T subscript s h i f t end subscript(s) 0.019
Start Simulation Time (s) 0
End Simulation Time (s) 0.04
Step Simulation Time (s) 0.0005
Angular Velocity (deg/s) 4500
Initial Angle (deg) 0
Table 4 - Properties of the On Load Study. 

The resulting on load torque versus time is illustrated in figure 9.
 

On Load Torque versus Time of the spoke type motor

Figure 9 - On Load Torque versus Time of the spoke type motor. 

b- Core Loss Results

The core loss has also been investigated. The non-linear AISI 1010 Steel material, applied for both the rotor and stator cores, has the Steinmetz loss coefficient as shown in table 5.

Coefficient Signification Value
Kh Hysteresis Loss Coeff. 2020
Kc Eddy Current Loss Coeff. 0.116
Ke Excess Loss Coeff. 3.31
Table 5 - Core Loss Coefficient for the AISI 1010 Steel Material 

The total core loss for the spoke type motor under study versus time is illustrated in figure 10.

Total Core Loss of the Spoke Motor versus Time

Figure 10 - Total Core Loss of the Spoke Motor versus Time. 

c- Magnetic field mappings of the Spoke Type Motor

The magnetic field of the spoke motor under on load condition and for an initial angular position of 0 degree is presented in figure 11.

Magnetic field mapping of the spoke type motor under no load conditions

Figure 11 - Magnetic field mapping of the spoke type motor under no load conditions. 

References 

[1] Website, https://www.eurekamagazine.co.uk/design-engineering-features/technology/cooling-technology-in-this-electric-spoke-motor-makes-it-more-efficient-and-lightweight/176765/.