Copper-Rotor Motors Built, Tested in India Field Experience Shows Motors Gain Efficiency, Run Cooler (continued) Results from tests on two of the 2-pole motors are shown in Tables 1 and 2 and on two 4-pole motors in Tables 3 and 4. As expected, the higher conductivity (copper) rotor material increased speed slightly (i.e., slip is reduced), and efficiency is increased by between about 1.3 and nearly four percentage points, a rather remarkable improvement considering that the motors hadn’t been optimized for copper. However, because copper's higher conductivity was not taken into account in the motor's slot design, there was a reduction in locked rotor torque (Table 5).4 Table 1. Test Results for 2-hp (1.5-kW), 415-V, 2-pole, 3-phase, 50-Hz Motors, Copper and Aluminum Rotors Rotor Material Load, % Input Power, W Speed, rpm Efficiency, % Copper 100 1824 2949 82.54 Aluminum 100 1856 2926 81.14 Copper 75 1440 2955 79.19 Aluminum 75 1456 2940 77.80 Table 2. Test Results for 5-hp (3.7-kW), 415-V, 2-pole, 3-phase, 50-Hz Motors, Copper and Aluminum Rotors Rotor Material Load, % Input Power, W Speed, rpm Efficiency, % Copper 100 4256 2947 87.09 Aluminum 100 4496 2925 83.99 Copper 75 3232 2960 85.99 Aluminum 75 3408 2935 82.19 Table 3. Test Results for 3-hp (2.2-kW), 415-V, 4-pole, 3-phase, 50-Hz-Motors, Copper and Aluminum Rotors Rotor Material Load, % Input Power, W Speed, rpm Efficiency, % Copper 100 2600 1451 85.88 Aluminum 100 2660 1411 83.55 Copper 75 1960 1465 84.15 Aluminum 75 2040 1433 82.82 Table 4. Test Results for 5-hp (3.7-kW), 415-V, 4-pole, 3-phase, 50-Hz Motors, Copper and Aluminum Rotors Rotor Material Load, % Input Power, W Speed, rpm Efficiency, % Copper 100 4344 1469 85.97 Aluminum 100 4544 1429 83.01 Copper 75 3280 1473 84.54 Aluminum 75 3400 1443 82.56 Table 5. Locked Rotor Torque and Temperature Rise in 2- and 4-pole Motors with Copper and Aluminum Rotors hp (Kw) Poles Rotor Material Locked Rotor Torque, % of rated torque Temp. Rise, °C (°F) 2 (1.5) 2 Cu 406.2 39.6 1,2 (103.3) 2 (1.5) 2 Al 442.2 36.8 1 (98.2) 5 (3.7) 2 Cu 174.0 66.7 1 (152.1) 5 (3.7) 2 Al 260.9 80.1 1 (176.2) 3 (2.2) 4 Cu 242.4 57.7 (135.9) 3 (2.2) 4 Al 268.4 68.8 (155.8) 5 (3.7) 4 Cu 168.4 61.8 (143.24) 5 (3.7) 4 Al 205.2 68.9 (156.0) 1 Measured at reduced voltage (353 V). 2 No cooling fins on this die-cast copper rotor. MORE >>

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