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Improving the efficiency of fracturing pump drive motors is key to improving the performance of fracturing equipment. For this purpose, this paper investigates the losses and efficiency of five-phase fracturing pump drive motors with different stator winding connections. Inverters generate different phase voltages in different stator winding connections, which leads to different spatial harmonics and losses. Of the various losses in the motor, the iron loss is hard to measure. Component theory is proposed, and a corresponding equivalent circuit is developed in this paper. Calculation of the iron loss based on the phase voltage of the different stator winding connections. In order to verify the validity of the equivalent circuit, the proposed model was simulated in MATLAB/Simulink and some experimental tests were carried out on several 15 kW motors. The results show that the total harmonic distortion (THD) coefficient of voltage and current is the smallest for the pentacle winding in the single winding, the voltage, and current THD coefficient is the smallest for the pentagon–star winding in the combine d winding. And according to the efficiency calculation, it can be seen that the fracturing pump drive motor with the pentagon–star winding is highly efficient and energy-saving, as well as having a high fault tolerance.

For the optimization of motor efficiency, a kind of control efficiency optimization of induction motor based on sliding mode variable structure is presented to solve the problem without considering the iron loss of motor vector control system. The parallel resistance motor loss model in the two-phase stationary coordinate is set up. The controller is designed based on the two order sliding mode, and solves the problem of chattering of sliding mode control for the correlation degree 1 by the super twisting algorithm. The stability of the control system is proved by Lyapunov stability theorem, and the gain parameter of controller is deduced. Matlab Simulink simulation shows that the efficiency optimization control method based on the sliding mode can reduce the motor loss, improve the operating efficiency of the motor, has good dynamic speed performance and good anti-interference performance and strong robustness. [ABSTRACT FROM AUTHOR]

• Modelling of precipitation effect on magnetic coercive field and iron losses. • Using JMAK law to assess the evolution of magnetic properties during ageing. • Integration of JMAK law into an iron loss model to predict magnetic ageing effect. This article deals with the modelling of iron losses due to the magnetic ageing of electrical steels used in energy conversion devices. This phenomenon is the consequence of irreversible mechanisms in the material which can be triggered by the operating temperature of electrical devices. At first, an experimental study is carried out at 180° C in order to assess the effect of isothermal ageing on electromagnetic properties of a magnetic steel sample. The results show that, during the thermal ageing, the hysteresis losses and the coercive field increase. These experimental observations, mainly caused by the formation of precipitates at the material microstructural scale, are then discussed. Considering the link between the effect of magnetic ageing on macroscopic magnetic properties (effect) and the microscopic precipitation (cause), the Johnson – Mehl – Avrami – Kolmogorov (JMAK) law describing the kinetics of precipitation was applied to model the time evolution of magnetic ageing. Once this approach was validated, it is proposed to integrate the JMAK law in the Steinmetz iron loss model. [ABSTRACT FROM AUTHOR]