Question

The following test data apply to a 7.5-hp, three-phase, 220-V, 19-A, 60-Hz, four-pole induction motor with a double-squirrel-cage rotor of design class C (high-starting-torque, low-starting current type): Test :No-load test at 60 Hz; Applied voltage V - 219 V line-to-line; Average phase current I, nl 5.70 A; Power Pnl -380 W; Test 2: Blocked-rotor test at 15 Hz; Applied voltage V 26.5 V line-to-line; Average phase current lbl 18.57 A; Power Pbl 675 W; Test 3: Average de resistance per stator phase (measured immediately after test Ri-0.2622; Test 4: Blocked-rotor test at 60 Hz; Applied voltage V 212 V line-to-line; Average phase current l,bl 83.3 A; Power Pbl 20.1 kW; Measured starting torque Tstart 74.2 N. m Compute the no-load rotational loss and the equivalent-circuit parameters applying to the normal running conditions. Assume the same temperature as in test 3. Neglect any effects of core loss, assuming that core loss can be lumped in with the rotational losses. a. b. Compute the electromechanical starting torque from the input measurements of test 4. Assume the same temperature as in test 3.