## 1 Introduction  
Induction motor (IM) is still one of the most widely used types of rotating electrical machine. The typical control of modern inverter-fed IM drives utilizes either the direct torque control (DTC) or field-oriented control (FOC) [1]. However, as another perspective strategy, the model predictive control (MPC) has received attention in recent years [2, 3, 4]. MPC aims to search for an optimal inverter voltage vector, which brings the system closest to the reference values. This optimum is mathematically expressed via the so-called cost function and is found analytically or by enumerating the whole feasible set. One of the typical MPC implementations in electric drives is predictive torque control (PTC), which regulates the developed torque and stator flux amplitude. The PTC avoids using a modulator, so only the eight fundamental voltage vectors are considered feasible candidates within a two-level inverter. This makes the searching for the optimal voltage vector more straightforward since the cost function must be enumerated only eight times. The torque and flux amplitude control approach using only eight voltage vectors remains the same for the DTC and PTC [4]. Because of this similarity, the drawback of increased current and torque ripple is also shared [5]. Several approaches suppressing the ripple were introduced in the literature. Most of them reduce the current ripple at the cost of increased switching frequency, i.e., shorter sampling time [6], variable switching point [7], or extended feasible set by space-vector modulation (SVM) [8], which is not admissible in many applications due to the increased switching losses. Other solutions are based on hardware modification, i.e., the utilization of multi-level inverters [9; 10] or adjustable DC-link voltage [11; 12]. The ability to suppress the current ripple by software without the switching frequency increase is possible only to some extent. Such an approach lies within the cost function design focused on the switching frequency decrease [6], the efficient zero voltage vector selection [13], or optimal duty-cycle control [3]. Moderate improvements were also achieved with an extended prediction horizon [6; 14]. The IMs utilized in the industry are designed to operate either in star or delta winding configuration. Online winding changeover techniques are a common practice either for inverter-fed [15; 16; 17; 18; 19; 20] or for direct-online (DOL) [21; 22; 23] operated electrical machines. Within DOL motors, star-delta switches are predominantly used to improve the motor power factor and efficiency. The primary purpose of winding configuration changeover in inverter-fed machines is to extend the base-speed range, either by a star-delta switch or using a center tap in the winding. The winding configuration can then be altered either with a mechanical contactor or semiconductor switch. This paper investigates another merit of winding changeover--the possibility of using an online delta-star winding switchover for the current and torque ripple reduction of a PTC-controlled IM drive. By switching from delta to star at a constant DC-link voltage, the inverter voltage vectors' magnitude is decreased by a factor \(\sqrt{3}\), which lowers the drive torque capabilities at higher speeds. On the other hand, the peak instantaneous motor phase voltage is reduced 1.5 times, and two voltage levels (\(\pm 1/3\) of the DC-link voltage) are added. This leads to lower current and torque ripple, and improved efficiency since the total harmonic distortion (THD) of the machine currents directly contributes to power losses [12; 24]. Publications on predictive control of IM drive (or control of IM drives in general) usually silently assume the use of a star-connected motor [25]. However, if the machine is delta-connected, the current and voltage transformations and the control algorithm have to be adjusted [26].