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 1: No-load test at 60 Hz; Applied voltage V = 219 V line-to-line; Average phase current I1,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 ll,bl = 18.57 A; Power Pbl = 675 W; Test 3: Average dc resistance per stator phase (measured immediately after test R1=0.262?; Test 4: Blocked-rotor test at 60 Hz; Applied voltage V = 212 V line-to-line; Average phase current l1,bl = 83.3 A; Power Pbl = 20.1 kW; Measured starting torque Tstart = 74.2 N. m a. 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. b. Compute the electromechanical starting torque from the input measurements of test 4. Assume the same temperature as in test 3.

Answer 1