Published 03/25/2025 at 1113 × 780 in Copper Rotor Motors: A Step toward Economical Super-Premium Efficiency Motors? Figure 2. Efficiency Curves for a 15-Hp Copper Rotor and Average of 5 x 15-Hp Energy Efficient Aluminum Rotor Motors Figure 2. Efficiency Curves for a 15-Hp Copper Rotor and Average of 5 x 15-Hp Energy Efficient Aluminum Rotor Motors