The following observations are made on a 3-phase, 50-Hz, Y-connected, 380 V rms line-to-line induction motor with negligible stator winding resistance.

The following observations are made on a 3-phase, 50-Hz, Y-connected, 380 V rms line-to-line induction motor with negligible stator winding resistance.

i) At no-load the motor is rotating at 745 rpm.

The following observations are made on a 3-phase, 50-Hz, Y-connected, 380 V rms line-to-line induction motor with negligible stator winding resistance.

i) At no-load the motor is rotating at 745 rpm.

a) What is the number of poles of the machine?

The following observations are made on a 3-phase, 50-Hz, Y-connected, 380 V rms line-to-line induction motor with negligible stator winding resistance.

i) At no-load the motor is rotating at 745 rpm.

The following observations are made on a 3-phase, 50-Hz, Y-connected, 380 V rms line-to-line induction motor with negligible stator winding resistance.

i) At no-load the motor is rotating at 745 rpm.

ii) The stator can not be started with a heavy load, but it only starts when the load torque is reduced to 236 Nm

The following observations are made on a 3-phase, 50-Hz, Y-connected, 380 V rms line-to-line induction motor with negligible stator winding resistance.

i) At no-load the motor is rotating at 745 rpm.

ii) The stator can not be started with a heavy load, but it only starts when the load torque is reduced to 236 Nm

iii) When the motor is running at rated speed, the load is gradually increased and it is found that the rotor speed reduced down to 600 rpm, but after it decelerates and stops.

The following observations are made on a 3-phase, 50-Hz, Y-connected, 380 V rms line-to-line induction motor with negligible stator winding resistance.

i) At no-load the motor is rotating at 745 rpm.

==> Number of poles=8

ii) Starting Torque = 236 Nm

iii) Maximum torque at 600 rpm.

b-c) Calculate the referred rotor resistance and total leakage reactance (stator+rotor)?

b-c) Calculate the referred rotor resistance and total leakage reactance (stator+rotor)?

d) If the rotational power is 1518 W, find the air-gap power, rotor copper loss, internal mechanical power and the net output power when the rotor is rotating at 712.5 rpm

b-c) Calculate the referred rotor resistance and total leakage reactance (stator+rotor)?

d) If the rotational power is 1518 W, find the air-gap power, rotor copper loss, internal mechanical power and the net output power when the rotor is rotating at 712.5 rpm

e) Calculate the efficiency at 712.5 rpm

Solutions

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Exercise-2

A 10 hp 3-phase, 60 Hz, 6-pole squirrel-cage induction motor is used to drive a load at a slip of 3%. The friction and windage torque is measured to be 6.1 Nm at this slip. The torque requirement of the load varies as the cube of its speed and is 67.4 Nm at 1200 rpm.

Exercise-2

A 10 hp 3-phase, 60 Hz, 6-pole squirrel-cage induction motor is used to drive a load at a slip of 3%. The friction and windage torque is measured to be 6.1 Nm at this slip. The torque requirement of the load varies as the cube of its speed and is 67.4 Nm at 1200 rpm.

Compute the electromagnetical torque (Te), the power transferred across the air-gap (Pg), adn the rotor copper loss (Pcu2).

Exercise-3

A 480 V, 50 hp induction motor is drawing 60 A at 0.85 pf lagging.

Exercise-3

A 480 V, 50 hp induction motor is drawing 60 A at 0.85 pf lagging. The stator copper losses are 2kW and the rotor copper losses are 700W.

Exercise-3

A 480 V, 50 hp induction motor is drawing 60 A at 0.85 pf lagging. The stator copper losses are 2kW and the rotor copper losses are 700W. The friction and windage losses are 600 W, the core losses are 1800 W and the stray losses are negligible, find:

Exercise-3

A 480 V, 50 hp induction motor is drawing 60 A at 0.85 pf lagging. The stator copper losses are 2kW and the rotor copper losses are 700W. The friction and windage losses are 600 W, the core losses are 1800 W and the stray losses are negligible, find:

• The air gap power.

Exercise-3

A 480 V, 50 hp induction motor is drawing 60 A at 0.85 pf lagging. The stator copper losses are 2kW and the rotor copper losses are 700W. The friction and windage losses are 600 W, the core losses are 1800 W and the stray losses are negligible, find:

• The air gap power.

• The converted power.

Exercise-3

A 480 V, 50 hp induction motor is drawing 60 A at 0.85 pf lagging. The stator copper losses are 2kW and the rotor copper losses are 700W. The friction and windage losses are 600 W, the core losses are 1800 W and the stray losses are negligible, find:

• The air gap power.

• The converted power.

• The output power.

Exercise-3

A 480 V, 50 hp induction motor is drawing 60 A at 0.85 pf lagging. The stator copper losses are 2kW and the rotor copper losses are 700W. The friction and windage losses are 600 W, the core losses are 1800 W and the stray losses are negligible, find:

• The air gap power.

• The converted power.

• The output power.

• The efficiency of the motor

Exercise-3

A 480 V, 50 hp induction motor is drawing 60 A at 0.85 pf lagging. The stator copper losses are 2kW and the rotor copper losses are 700W. The friction and windage losses are 600 W, the core losses are 1800 W and the stray losses are negligible, find:

• The air gap power.

• The converted power.

• The output power.

• The efficiency of the motor

• Torque of the motor

Exercise-3

A 480 V, 50 hp induction motor is drawing 60 A at 0.85 pf lagging. The stator copper losses are 2kW and the rotor copper losses are 700W. The friction and windage losses are 600 W, the core losses are 1800 W and the stray losses are negligible, find:

• The air gap power.

• The converted power.

• The output power.

• The efficiency of the motor

• Torque of the motor

• Rotational speed of the rotor

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