Question

A three-phase, 230-V, 60Hz, Y-connected induction motor was tested for no-load and locked-rotor tests. The test data is presented below.

No-load test Fixed (locked) rotor test

Input power 130W 65W

Line current 0.45 A 1.2 A

Line voltage 230 V 47 V

Friction and wind losses 15 W

Resistance (stator in DC between two terminals = 4.1 W

Determine the parameters of the equivalent circuit of the motor.

Answer 1

To determine the parameters of the equivalent circuit of the motor, we need to calculate the resistance of the stator, reactance of the stator, friction and wind losses, no-load current, locked rotor current, total impedance, X/R ratio, and equivalent resistance.

Step-by-step explanation:

To determine the parameters of the equivalent circuit of the motor, we need to calculate the following:

1. Resistance of the stator: 4.1 Ω
2. Reactance of the stator: 0 (since it is Y-connected)
3. Friction and wind losses: 15W
4. No-load current: 0.45A (from the no-load test)
5. Locked rotor current: 1.2A (from the locked rotor test)
6. Total impedance: The total impedance can be calculated as: Z = V/I, where V is the line voltage and I is the line current. For the no-load test, Z = 230V/0.45A = 511 Ω. For the locked rotor test, Z = 47V/1.2A = 39.17 Ω.
7. X/R ratio: The X/R ratio can be calculated as: X/R = Z/X, where Z is the total impedance and X is the reactance of the stator. Since X = 0, the X/R ratio is also 0.
8. Equivalent resistance: The equivalent resistance can be calculated as: R_eq = V/I, where V is the line voltage and I is the line current. For the no-load test, R_eq = 230V/0.45A = 511 Ω. For the locked rotor test, R_eq = 47V/1.2A = 39.17 Ω.

Therefore, the parameters of the equivalent circuit of the motor are:

• Resistance (stator): 4.1 Ω
• Reactance (stator): 0 Ω
• Friction and wind losses: 15W
• No-load current: 0.45A
• Locked rotor current: 1.2A
• Total impedance: 39.17 Ω
• X/R ratio: 0
• Equivalent resistance: 39.17 Ω