# Energy Efficiency Analysis of Fixed-Speed Pump Drives with Various Types of Motors
## 3 Assessment of the Energy Consumption of the Pump Unit
(**b**) Energy cost savings over electric motor No. 8. 1—LSPMSM IE4 SEW DRU J; 2—LSPMSM IE4 Synchrotron; 3—LSPMSM IE4 Weg WQuatrro; 4—IM IE4 Siemens 1 LE1004; 5—IM IE4 Weg W22; 6—IM IE3 Siemens 1 LE1003; 7—IM IE3 Weg W21; 8—IM IE3 ABB M3 BP. Figure 6: Energy cost savings over electric motor No. 8 (for numbers of the motors see the caption of Figure 5). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Type of Motor** & \(\mathbf{E_{d,m}}\) **(kW-h)** & \(\mathbf{E_{y,m}}\) **(kW-h)** & \(\mathbf{C_{y,m}}\) **(€)** & \(\mathbf{C_{LCCen,m}}\) **(k€)** & \(\mathbf{S_{y,m}}\) **(€)** \\ \hline
1. LSPMSM SEW DRU J & 29.1 & 10,635 & 2113.1 & 34.55 & 73.8 \\
2. LSPMSM SynchroVERT & 28.9 & 10,535 & 2093.3 & 34.23 & 93.6 \\
3. LSPMSM WEG WQuatrro & 29.8 & 10,882 & 2162.3 & 35.36 & 24.6 \\
4. IM Siemens 1 LE1004 & 29.0 & 10,585 & 2103.1 & 34.39 & 83.8 \\
5. IM WEG W22 & 29.1 & 10,630 & 2112.1 & 34.54 & 74.8 \\
6. IM Siemens 1 LE1003 & 29.6 & 10,822 & 2150.3 & 35.16 & 36.6 \\
7. IM WEG W21 & 29.7 & 10,843 & 2154.4 & 35.23 & 32.5 \\
8. IM ABB M3 BP & 30.2 & 11,006 & 2186.9 & 35.76 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Cost characteristics of the power consumption. The results shown in Figure 5a,b are a consequence of the fact that, according to the adopted standard [6], electric motors are classified in accordance with the efficiency in the rated mode (a load of 100%). However, in pump units, electric motors run at 2-4 times lower power than their rated value for a significant part of the time, and as a result, exhibit a reduced efficiency. At the same time, the existing standards do not establish the minimum efficiencies at loads below the rated value for electric motors powered directly from the mains. Thus, the selection of an electric motor based on its IE energy efficiency class will not necessarily result in minimum energy consumption in a number of applications, such as variable flow pumps. It should be noted that for frequency-controlled electric motors, the IEC 60034-30-2 standard [30] establishes the efficiencies in seven load modes different from the rated mode. In the draft version of the IEC 60034-30-2 standard [31], it was proposed that the total efficiency be calculated for frequency-controlled electric motors of pumps and fans (drives with a quadratic torque-speed dependence) as the average efficiency coefficient at reduced speeds and loads. Figure 6 shows the energy cost savings over the worst case of electric motor No. 8 (in %). Therefore, when selecting an electric motor for a pump unit operating with a variable flow, one should not be guided only by the IE energy-efficiency class and the rated efficiency value; instead, one should calculate the energy consumption depending on the operating conditions or should take into account the energy efficiency index of the pump unit (see Section 4). It is worth noting that LSPMSMs have a higher cost compared to IMs (especially IE3 class) due to the use of expensive rare-earth magnets in its design. The process of obtaining rare-earth elements from raw ore is associated with significant environmental damage, and in de Lima [32], it is claimed that the production of each ton of rare-earth element material results in the generation of 1-1.4 tons of radioactive waste. Only a small part of the resulting slush contains rare-earth elements and is subsequently extracted for refinement [32]. There is also a technological dependence on rare-earth element suppliers from China, as more than 95% of the world's rare-earth element mining is controlled by China [33]. In the current situation on the market, the prices of rare-earth elements are unstable and can change several times over several years [34]. Also, the difficulty in starting up LSPMSMs at a significant load moment of inertia severely limits their potential applications.