*3.2. Changes in the Performance of SCIMS*

It was not just the masses and volumes that changed. Successive changes in the performance of SCIMs occurred from the first commercially available versions to the mass manufacturing versions of today (2022).

Several technological advances explained the changes in the performance of SCIMs, from the technological innovations already mentioned to improvements in production processes and the purification of active materials. Sven Sjöberg [66] presented the reasons for the performance gains of SCIMs manufactured by the company ABB Motors after the great cycle of innovations that closed in the 1970s:


Sven Sjöberg (1997) presented the performance changes to SCIMs manufactured by ABB Motors between 1935 and 1996, as shown in Figure 11. According to Sven Sjöberg, performance changes did not result from any performance regulation but occurred due to materials improvements, technological innovations, and improvements in production processes [66].

**Figure 11.** Changes to performance of 4-pole SCIMs between 1935 and 1996. Source: adapted from [65,66].

It is observable in Figure 10 that in the 1960s and 1970s there was a reduction in the average performance of SCIMs, considering a wide range of power. In some periods, the performances were inferior to those obtained by the industry in 1935. The researcher Sven Sjöberg, in his text, does not identify the elements that led to this temporary drop in performance between the 1970s and 1980s.

For the United States Department of Energy (DOE), the 1960s and 1970s were periods of global economic crisis, where SCIM manufacturers built lower-cost equipment compared to previous years. These SCIMs were less efficient, as shown in Figure 12, as they minimized the use of materials such as copper, aluminium, and steel. According to the DOE, these SCIMs had lower initial costs than previous projects. However, they consumed more electrical energy due to their inefficiency, so their use throughout the life cycle was more expensive [85].

**Figure 12.** Changes to performance of 4-pole SCIMs between 1944 and 2012. Source: adapted from [85].

Figure 12 shows that the four-pole SCIMs manufactured and marketed in North America in the 1980s had even lower performance than SCIMs manufactured in 1944, which were the first officially registered by the DOE.

According to the DOE, less-efficient and more-compact SCIMs became possible with insulating materials that could withstand high temperatures. These SCIMs were designed to admit higher losses due to the increase in temperature in the coils located in the stator, making it possible to accommodate the winding wires in smaller frames without damaging the insulation [85].

Figure 13 shows the performance changes to four-pole SCIMs with motor rated output powers of 37 and 45 kW, operating at 50 or 60 Hz, at low voltage.

Figure 13 shows the average performance presented by Sjöberg and the DOE. The SCIMs showed a performance reduction between the 1960s and 1980s, and only the data provided by WEG (2015) showed a continuous increase in performance. Figure 13 illustrates the performance data available in the company's publications, beginning in 1960, which was the year the company was established. The data show performances below those obtained in the international market, with high performances recorded for 2010.

**Figure 13.** Changes to performance of 4-pole SCIM performance between 1935 and 2012. Source: adapted from [65,66,85].
