**6. High power vehicles**

When the required power of the vehicle motorisation exceeds the threshold of 30 kW (approximate), it becomes difficult, if not impossible, to supply the motor with a single controller because the phase currents become prohibitive at VLV. The two examples discussed in this paragraph show how to solve this problem using power partitioning.

#### **6.1 Sporty electric vehicle**

The first considered case of high power motorisation is that of a rally type sporty vehicle (**Figure 21**).

**Figure 21.** *Sporty full electric vehicle.*

*High Power Very Low Voltage Electric Motor for Electric Vehicle DOI: http://dx.doi.org/10.5772/intechopen.99134*

The simplified specifications of the motor are as follows:


In order to divide the power supplied to the motor, the winding was designed based on the technique described earlier in **Figure 15**, and is split into two electrically isolated stars, as depicted in the following **Figure 22**; each half-winding being fed by a dedicated controller and delivering half of the total required power.

**Table 6** summarises all the main characteristics of the electric motor. In this case, we are using the solid bar configuration corresponding to case 3 in **Table 2**.

The losses at simultaneously maximum power and maximum speed are too high, more than 7 kW, particularly due to a high KAC coefficient, but this is only a transient regime occurring during the acceleration phase. Again, here the steady-state thermal behaviour also depends on the nature of the track which cannot be defined a priori, but in all cases the efficiency is high and greater than 95%. However, at low speed acceleration, the copper losses are halved at constant current because the KAC coefficient tends towards 1, the efficiency, therefore, remains high over a wide speed range. The partition of the power on multiple converters makes it possible to reduce the phase current to 650 A during the transient regime. The bar winding has allowed the design of a very compact motor reaching high power density (4 kW / kg in transient regime).

#### **6.2 Utility vehicle**

The second example of power partitioning is that of an utility vehicle, an electric tractor for winegrowers (**Figure 23**).

This tractor is equipped with four electrified wheels fully independent. The topology of the motors is very similar to that described in section 4. The solid bars configuration corresponds to line 4 of **Tables 1** and **2**. The four electric motors drive the wheels via a gearbox with a reduction ratio of 1/40.

The simplified specifications of the motors are as follows:


**Figure 22.** *Dual stars winding layout.*


#### **Table 6.**

*Characteristics of the sporty vehicle electric motor.*

**Figure 23.** *Electric tractor.*


*High Power Very Low Voltage Electric Motor for Electric Vehicle DOI: http://dx.doi.org/10.5772/intechopen.99134*

The nominal operating condition of the electric tractor corresponds to the ploughing phase, where the displacement speed is low and the total required mechanical power does not exceed 20 kW. The tractive force applied on the plough is approximately 16 kN. The sizing was carried out based on the tractor behaviour with a conventional thermal engine.

The power partition, via the use of four electric motors, enables to have a significant power available for the transient mode, approximately 160 kW, thanks to the capacity of over-torque necessary for obstacles clearing and vehicle overspeed during the road trips. During the latter operating conditions, the motors are running without flux weakening. However, this high power is only used very rarely, and only temporarily, in the case of transporting heavy loads on steeply sloping roads.

The efficiency of each electric motor at the nominal conditions, at low speed and at an output torque of 50 Nm per motor, is about 95% and this because the copper losses in the 24 mm<sup>2</sup> solid bars are very low due to the very low electrical frequency (133 Hz).

### **7. Conclusion**

According to the various examples discussed in this chapter, it can be seen that it is possible to design an electric vehicle drive train operating at very low voltage (battery voltage below 120 VDC) and over a wide power range (up to 100 kW). An original, compact and high efficiency motorisation solution using a solid bar winding has been presented. In all the cases, the sizing constraints of the motor controller have been taken into account.

#### **Main symbols and abbreviations**


*New Perspectives on Electric Vehicles*
