This paper has discussed some parameters that affect the efficiency of the power train used in electrical vehicles, mainly affected by the electrical motor, considering PMSM (permanent-magnet synchronous motor) and induction motor that are the most used in this kind of applications. The efficiency is a key subject affecting directly the electrical vehicle autonomy. In a first analysis, it has been shown how the PI coefficients used in the speed controller affect the energy needed to change the motor steady state (acceleration and braking in vehicle application), being necessary an increase of the input energy up to 20% if these coefficients are not selected correctly. In a second analysis, the influence of the switching frequency in the driver total losses, which include the electronic converter and electrical motor losses, has been evaluated. It has been shown that there is a value of switching frequency that minimises the total losses; under this value the electrical losses will cause an increase in the total losses and above, the total losses increase due mainly to the increase of the converter losses. For the case of the PMSM, the switching frequency that minimised these total losses is near 1 kHz, that is a value much lower than the value usually recommended by manufacturers. By selecting this low switching frequency, a total losses reduction of nearly 30% can be achieved. This value of switching frequency that minimises the total losses does not depend on the motor speed, as it has been shown through experiments for the induction motor. This result has to be taken into account when selecting the most convenient switching losses to operate the set converter and motor. In some cases, the designer selects the value of the switching converters to achieve that the motor currents be sinusoidal with a low THD, but these selections could produce a total losses value greater than the optimal value (due to the converter losses). Following the results presented in this study, one can conclude that in some case it is better to not achieve low THD in currents, but to minimise the total losses (taking into account that these losses are produced by the motor and the electronic converter). Because of the similarity of the results of the experimental test and the simulation in PSIM (Physical Security Information Management Software), using the induction motor, it is possible to draw an analogy with the PMSM comparing the test carried out in PSIM platform to the future experimental results (currently developing).