P1. Determine the number of poles, the slip, and the frequency of the rotor currents at the rated load for three-phase induction motors rated at: (a) 2200 V, 60 Hz, 588 rpm. (b) 120 V, 600 Hz, 873 rpm.

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Chapter35: Harmonics 916
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INDUCTION MACHINES
PROBLEMS
P1
Determine the number of poles, the slip, and the frequency of the rotor currents
at the rated load for three-phase induction motors rated at:
(a) 2200 V, 60 Hz, 588 rpm.
(b) 120 V, 600 Hz, 873 rpm.
P2.
The full-load speed of a 25 Hz induction motor is 720 rpm, while its no-load speed
is 745 rpm. Find the slip at full load.
P3.
A 50 hp, three-phase, 60 Hz, wye-connected induction motor operates at a shaft
speed of almost 900 rpm at no load and 873 rpm at full load. Determine the
following:
(a) The number of poles of the motor
(b) The per-unit and percent slip at full load
(c) The slip frequency of the motor
(d) The speed of the rotor field with respect to the rotor itself
(e) The speed of the rotor field with respect to the stator
(f) The speed of the rotor field with respect to the stator field
(g) The shaft torque of the motor at full load
P4.
The following data is read on the name plate of a three-phase cage induction motor:
output power Pout = 3 kW, input frequency f = 50 Hz, speed n = 2800 rpm, voltage
V₁ = 380 V (line-to-line), efficiency n = 80%, power factor cosp = 0.92. If the
stator windings are Y-connected, find:
1) the number of poles 2p, and the slip s,
2) the input current Is, and input power Pin.
3) the mechanical power Pm and electromagnetic power Pem. given rotational
losses Prot 120 W,
4) the shaft torque T and the electromagnetic torque Tem.
P5.
A three-phase, 480 V, 25 hp, two-pole 60 Hz induction motor has a full-load slip
of 5%. Determine the following:
(a) The synchronous speed of the motor
(b) The rotor speed at full load.
(c) The slip frequency at full load
Transcribed Image Text:INDUCTION MACHINES PROBLEMS P1 Determine the number of poles, the slip, and the frequency of the rotor currents at the rated load for three-phase induction motors rated at: (a) 2200 V, 60 Hz, 588 rpm. (b) 120 V, 600 Hz, 873 rpm. P2. The full-load speed of a 25 Hz induction motor is 720 rpm, while its no-load speed is 745 rpm. Find the slip at full load. P3. A 50 hp, three-phase, 60 Hz, wye-connected induction motor operates at a shaft speed of almost 900 rpm at no load and 873 rpm at full load. Determine the following: (a) The number of poles of the motor (b) The per-unit and percent slip at full load (c) The slip frequency of the motor (d) The speed of the rotor field with respect to the rotor itself (e) The speed of the rotor field with respect to the stator (f) The speed of the rotor field with respect to the stator field (g) The shaft torque of the motor at full load P4. The following data is read on the name plate of a three-phase cage induction motor: output power Pout = 3 kW, input frequency f = 50 Hz, speed n = 2800 rpm, voltage V₁ = 380 V (line-to-line), efficiency n = 80%, power factor cosp = 0.92. If the stator windings are Y-connected, find: 1) the number of poles 2p, and the slip s, 2) the input current Is, and input power Pin. 3) the mechanical power Pm and electromagnetic power Pem. given rotational losses Prot 120 W, 4) the shaft torque T and the electromagnetic torque Tem. P5. A three-phase, 480 V, 25 hp, two-pole 60 Hz induction motor has a full-load slip of 5%. Determine the following: (a) The synchronous speed of the motor (b) The rotor speed at full load. (c) The slip frequency at full load
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