Finding motor line current and induced e.m.f?

In summary, for a 400 V, 10 HP, 3-phase synchronous motor with negligible armature resistance and a synchronous reactance of 10 Ω/phase, the line current is 0.833 A and the corresponding induced e.m.f at full load is 408.33 V. The efficiency of the motor is 85% and the calculated induced e.m.f at unity power factor is 263.5 V with an angle of -28.7° between the e.m.f and current.
  • #1
RegardedBody
2
0
1. A 400 V, 10 HP, 3-phase synchronous motor has negligible armature resistance and a synchronous reactance of 10 Ω/phase. The motor runs at unity power factor. Determine the motor line current and the corresponding induced e.m.f for full-load conditions. The efficiency of the motor is 85%



2. P=[itex]\sqrt{3}[/itex] VI

EGP (unity) = [itex]\sqrt{ (V+IR)^2 + (IX)^2}[/itex]

3. I tried isolating for current using the first formula then used that value in the second formula but got the wrong answer.
The correct answer is supposed to be EGP= 263.5 angle=-28.7 degrees. Please help guys :(
 
Physics news on Phys.org
  • #2
Answer: The line current of the motor is given by,I = P/(3V) = 10 HP/(3*400 V) = 0.833 A The induced e.m.f for full load conditions can be calculated using the equation,EGP = V + I X = 400 V + 0.833 A * 10 Ω = 400 V + 8.33 V = 408.33 V The power factor for this motor is unity and hence the angle between the e.m.f and current is zero. The corresponding induced e.m.f at the rated power factor is given by,EGP = \sqrt{ (V+IR)^2 + (IX)^2} = \sqrt{ (400 + 0.833*0)^2 + (0.833*10)^2 } = 263.5 V The angle between the e.m.f and current is -28.7°.
 

What is motor line current?

Motor line current refers to the amount of electrical current that flows through the motor's power supply lines. It is an important parameter to measure and monitor in order to ensure the proper functioning of the motor.

What factors affect motor line current?

The motor line current is affected by various factors such as the motor's design, the load it is operating under, and the input voltage. Other factors such as the motor's temperature, speed, and efficiency can also have an impact on the line current.

How can I calculate motor line current?

Motor line current can be calculated using Ohm's law, which states that current is equal to the voltage divided by the resistance. In a motor, the resistance is typically very low, so the current can be calculated by dividing the voltage by the motor's impedance.

What is induced e.m.f in a motor?

Induced electromotive force (e.m.f) in a motor refers to the voltage that is generated in the motor's windings as a result of the changing magnetic field produced by the motor's rotation. This voltage is responsible for creating the motor's torque and driving its rotation.

How can I measure induced e.m.f in a motor?

Induced e.m.f can be measured using a voltmeter or multimeter, by connecting the probes to the motor's terminals. The voltage reading will give an indication of the induced e.m.f, which can then be used to calculate the motor's speed or other parameters.

Similar threads

  • Engineering and Comp Sci Homework Help
Replies
4
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
4
Views
3K
  • Engineering and Comp Sci Homework Help
Replies
2
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
7
Views
1K
  • Engineering and Comp Sci Homework Help
Replies
8
Views
6K
  • Engineering and Comp Sci Homework Help
Replies
9
Views
1K
  • Engineering and Comp Sci Homework Help
Replies
4
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
6
Views
1K
  • Engineering and Comp Sci Homework Help
Replies
5
Views
2K
Replies
2
Views
432
Back
Top