T rated90 20lbf ft ⋅ = T rated90 n s60 n s90 T rated ⋅ = HP rated90 10hp = HP rated90 HP 60 = n s90 2700 min = n s60 1800 min = c. Above rated frequency, the motor operates at rated voltage and current, so rated power can be produced. Since the speed increases, rated torque will drop HP 30 5hp = HP 30 30 60 HP 60 ⋅ = T rated30 30 lbf ⋅ ft ⋅ = b. Below rated frequency, the motor can produce rated torque since the flux is constant. The hp is directly proportional to frequency T rated 30 lbf ⋅ ft ⋅
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