Induction Motors with Copper Rotor: A New Opportunity for Increasing Motor Efficiency

The content of this introductory paper is based on the article "[Title of the paper: Induction motors with copper rotor: a new opportunity for increasing motor efficiency]" published by [Publisher: International Journal of Electrical and Computer Engineering (IJECE)].

1. Overview:

  • Title: Induction motors with copper rotor: a new opportunity for increasing motor efficiency
  • Authors: Percy R. Viego Felipe, Vladimir Sousa Santos, Julio R. Gómez Sarduy, José P. Monteagudo Yanes, Enrique Ciro Quispe
  • Publication Year: 2023
  • Publication Journal/Academic Society: International Journal of Electrical and Computer Engineering (IJECE)
  • Keywords: Copper rotor induction motor, Economic feasibility, Electric motors, Energy efficiency, High-efficiency motors

2. Abstract:

The copper rotor induction motor (CURIM) was recently introduced because it has lower rotor fusion losses than the aluminum rotor (ALRIM). Furthermore, with CURIM, it is easier to reach IE4 and IE5 efficiency levels. The CURIM is advantageous for compact motors, escalators, and electric vehicle applications. However, CURIMs present slip, power factor, temperature increase, and torque decrease problems that must be analyzed. This study compared the economic feasibility of using CURIM with ALRIM by applying discount techniques. A case study was carried out in a sugar company with a cyclical operation, where 5.5 kW motors will be installed in the intermediate conductors of the mill's feeders. The facility works three shifts between 3 and 6 months. The cost increase (ACI) of CURIM over ALRIM was between 1.1 and 1.5 times. With 3,600 h/year and 4,000 h/year of operation, the ACI greater than 10%, it was found that the payback is more than four years, and the net present value (NPV) grows linearly.

3. Introduction:

A significant reduction in rotor losses is achieved using copper rotor induction motors (CURIM) instead of aluminum rotor induction motors (ALRIM). This is mainly because the electrical conductivity of copper is approximately 170% that of aluminum; therefore, the total machine losses also decrease. In a medium power induction motor, from 15% to 25% of the total losses, the efficiency increases from 2% to 5% [1], [2]. However, problems regarding the copper casting process have had to be solved first due to the high melting temperature of copper compared to aluminum (1,083 °C for copper compared to 660 °C for aluminum). The fundamental difficulties that appeared were shortened life of the die, oxidation in the casting process of pure copper, and porosity distributed in the molten copper [2].

As the electric power cost grew, awareness grew that the motor life cycle cost is essential, and consumers realized the convenience of paying a higher initial cost for more efficient motors [3]. Additionally, a driving factor has been government regulations and incentives. So, many companies and associations have worked to eliminate the drawbacks of copper casting and have developed die materials and casting processes for rotor manufacturing, which have made mass production possible and economical [1], [2], [4].

4. Summary of the Study:

Background of the Research Topic:

The copper rotor induction motor (CURIM) was recently introduced because it has lower rotor fusion losses than the aluminum rotor (ALRIM). Furthermore, with CURIM, it is easier to reach IE4 and IE5 efficiency levels. The CURIM is advantageous for compact motors, escalators, and electric vehicle applications.

Status of Previous Research:

Problems regarding the copper casting process have had to be solved first due to the high melting temperature of copper compared to aluminum (1,083 °C for copper compared to 660 °C for aluminum). The fundamental difficulties that appeared were shortened life of the die, oxidation in the casting process of pure copper, and porosity distributed in the molten copper [2].

Purpose of the Study:

This paper compares CURIMs with ALRIMs based on construction characteristics and associated costs, operation, losses, electromechanical, energy, and temperature characteristics. Finally, an economic feasibility study of replacing a 5.5 kW motor in a sugar factory is conducted by comparing the results of replacing a CURIM with an ALRIM of equal capacity.

Core Study:

The study carried out on the copper casting process at CURIM indicates that the cost of designing, casting, and installing a copper rotor motor of a specific type (that is, rated power, number of poles, voltage) built by a manufacturer, may differ from the cost of another manufacturer.

5. Research Methodology:

Research Design:

A case study was carried out in a sugar company with a cyclical operation, where 5.5 kW motors will be installed in the intermediate conductors of the mill's feeders. The facility works three shifts between 3 and 6 months.

Data Collection and Analysis Methods:

The economic analysis was carried out in a case study using the criterion of the differential net present value (Differential NPV) [27] so that the equal or almost equal costs are eliminated (for example, those related to the cost of the stator, those of installation, maintenance).

Research Topics and Scope:

Economic feasibility study of replacing a 5.5 kW motor in a sugar factory is conducted by comparing the results of replacing a CURIM with an ALRIM of equal capacity.

6. Key Results:

Key Results:

  • Table 1. Average loss segregation in seven CURIMs of 11.2 kW [5]
  • Table 2. Other performance characteristics of the 11.2 kW motor [5]
  • Table 3. Measured torque values for the 11.2 kW motor [5]
  • Table 4. Efficiency increase and total loss reduction in various CURIM compared with ALRIM [5]
  • Table 5. Comparison between Al and Cu compact rotors 75 kW motors [2]
  • Table 6. Parameters for 11 kW, six pole escalator copper rotor motor [2]
  • Table 7. Parameters for a 160 kW electric vehicle [2]
  • Table 8. Parameters for economic analysis using the differential NPV method for a 5.5 kW motor [27]
Figure 1. NPV and Payback period function as the initial incremental cost for 4,000 h of operation
Figure 1. NPV and Payback period function as the initial incremental cost for 4,000 h of operation
Figure 2. Payback period and NPV as a function of initial differential cost and 8,000 hours of operation
Figure 2. Payback period and NPV as a function of initial differential cost and 8,000 hours of operation
Figure. 3. NPV and payback period as a function of initial incremental cost and variable operating time
Figure. 3. NPV and payback period as a function of initial incremental cost and variable operating time

Figure Name List:

  • Figure 1. NPV and Payback period function as the initial incremental cost for 4,000 h of operation
  • Figure 2. Payback period and NPV as a function of initial differential cost and 8,000 hours of operation
  • Figure. 3. NPV and payback period as a function of initial incremental cost and variable operating time

7. Conclusion:

The study evaluated the advantages and disadvantages of CURIMs, as one of the new technological improvements of induction motors to increase energy efficiency. As a result, it was possible to show that the copper losses of the rotor, friction, and beating, and the additional losses are lower in the CURIM than in the ALRIM, and therefore the efficiency is higher.

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9. Copyright:

  • This material is a paper by "[Percy R. Viego Felipe]". Based on "[Induction motors with copper rotor: a new opportunity for increasing motor efficiency]".
  • Source of the paper: [DOI: 10.11591/ijece.v13i3.pp2409-2418]

This material is summarized based on the above paper, and unauthorized use for commercial purposes is prohibited.
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Tags: Applications; , CAD; , Copper Rotor; , Die casting; , Efficiency; , 고효율 모터; , 자동차