1. Problem # 5-7
A 3-phase, 8-pole, induction motor, rated at 874rpm, 30hp, 60Hz, 460V, operating at reduced load, has a shaft speed of 880 rpm. The combined stray power loss, windage loss, and friction loss is 350W. The rotor parameters in Ω/phase are
R1= R2=0.191 XM=14.18
X1=1.338 X2= Rfe=189.1
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2. Equivalent Circuit for an Induction Motor with all parameters referenced to the stator
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3. Need to determine the value of s.
Problem # 5-7 continued
The motor is NEMA Design C and Y-connected.
Determine
the motor input impedance/phase
Need to determine the value of s.
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6. The Input Impedance per Phase
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7. Solution continued
Determine the line current
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8. 3-Φ Delta and Wye Connections
(a) shows the sources (phases) connected in a wye (Y).
Notice the fourth terminal, known as Neutral.
(b) shows the sources (phases) connected in a delta (∆).
Three terminals
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9. Solution continued
Determine the active, reactive, and apparent power and power factor
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10. Solution continued
Determine the equivalent rotor current
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11. Solution continued
Determine the stator copper loss
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12. Solution continued
Determine the rotor copper loss
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13. Solution continued
Determine the core loss
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14. Solution continued
Determine the air gap power
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15. Solution continued
Determine the mechanical power developed
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16. Solution continued
Determine the developed torque
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17. Solution continued
Determine the shaft horsepower
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18. Solution continued
Determine the shaft torque
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19. Solution continued
Determine the efficiency
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20. Solution continued Sketch the power flow diagram and enter all data
24.33hp
631.5W W W W
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21. Solution continued
Determine the expected minimum locked-rotor torque, breakdown torque, and pull-up torque
From Table 5-1, Tlr=200%Trated
Tlr = (2)(180.27) = lb-ft
From Table 5-3, Tbreakdown = 190%Trated
Tbreakdown = (1.9)(180.27) = lb-ft
From Table 5-6, Tpull-up = 140%Trated
Tpull-up = (1.4)(180.27) = lb-ft
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