Alternator Problems (3 phase and single phase AC Motor)

In summary: Find the number of armature conductors in series per phase required for 3 phase, 10 pole alternator when driven at a speed of 600 RPM. Armature has 90 slots and armature winding is star connected to give induced emf of 11KV between lines. Assume flux per pole as 16 mwb?3. Find the number of armature conductors in series per phase required for 3 phase, 10 pole alternator for a 3 MW load when driven at a speed of 600 RPM. Armature has 100 slots and armature winding is star connected to give induced emf of 12.5KV between lines. Assume flux per pole as 20 mwb?4. Find the number of armature conductors in
  • #1
asteg123
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Homework Statement



1. A 4MVA, 13.3kV, 60Hz, 3 phase, delta-connected alternator has an effective resistance of 5.2 ohm/phase and a combined armature reactance of 54 ohm/phase. Determine the full-load generated voltage per phase, a. At unity pf, b. at 0.8 pf lagging, and at 0.866 leading pf.

2. A 750kVA, 2300V, delta-connected, 3-phase alternator has had open and short circuit tests performed and the following date were obtained:

Short Circuit test

Field current = 31.5A
Line current = rated

Open-circuit test

Field-current = 31.5A
Line voltage=1050V

The dc resistance across the terminals was measured at 0.38 ohm. Calculate the V.R. at 0.8pf lagging.

3. Calculate the open circuit votlage of a 3phase, star-connected alternator, 4 pole, 60Hz, 120 slots with each slot having 6 conductors in two layers. The machine is running at 1800rpm with a flux per pole of 125 milliWeber. The coil span is 12.

4. A single phase alternator, 50kVA, 460V supplies the rated load at 0.88 pf lagging. The dc resistance across the terminals ais 0.5 ohm and the synchronous reactance is 2.5 ohm. Calculate the angle of the power.


Homework Equations





The Attempt at a Solution



I have completely no idea on how to solve these problems...

I don't need the direct answers, I just want you guys to help me solve it, more on the procedure of solving it. Suffice to say, i want you guys to guide me in solving these problems.
 
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  • #2


you know, I'm also wondering how to solve this exact 4 questions..

are you my classmate or something?!

i hope someone solves this ASAP.. coz I'm really desperate.. i need the solutions by tom.. :cry:
 
  • #3
1. Find the number of armature conductors in series per phase required for 3 phase, 10 pole alternator when driven at a speed of 600 RPM. Armature has 90 slots and armature winding is star connected to give induced emf of 11KV between lines. Assume flux per pole as 16 mwb?
 
  • #4
hey guys please help me in above problem...
 
  • #5


I understand the importance of being able to solve problems and analyze data in order to gain a deeper understanding of a system or phenomenon. In the case of alternator problems, it is important to have a solid understanding of the principles of electromagnetism and circuit analysis in order to effectively solve these problems.

For the first problem, we are given the parameters of a 3 phase, delta-connected alternator and asked to determine the full-load generated voltage per phase at different power factors. To solve this, we will need to use the equations for calculating voltage, which is V=IZ, where V is voltage, I is current, and Z is impedance. We will also need to use the power factor formula, which is cosφ=P/S, where φ is the power factor, P is the active power, and S is the apparent power.

a. To determine the full-load generated voltage per phase at unity power factor, we can use the formula V=IZ=I(R+jX), where R is the effective resistance and X is the combined armature reactance. Plugging in the values given, we get V=I(5.2+j54). Since the alternator is delta-connected, the line voltage is equal to the phase voltage, so the full-load generated voltage per phase at unity power factor is 13.3kV.

b. To determine the full-load generated voltage per phase at 0.8 power factor lagging, we can use the power factor formula to find the reactive power, Q, and then use the equation V=I(R+jX) to find the voltage. Plugging in the values given, we get Q=13.3*10^6*0.8*tan(cos^-1(0.8))=8.7MVAr. Using the equation V=I(R+jX), we get V=I(5.2+j54+8.7j). Solving for I, we get I=1.3kA. Plugging in this value for I in the original equation, we get V=13.3kV+j8.7kV. The full-load generated voltage per phase at 0.8 power factor lagging is therefore 14.4kV.

c. To determine the full-load generated voltage per phase at 0.866 power factor leading, we can follow a similar procedure as in part b, but with a negative value
 

Related to Alternator Problems (3 phase and single phase AC Motor)

1. What are the common symptoms of alternator problems?

The most common symptoms of alternator problems include dimming or flickering headlights, a dead battery, strange noises coming from the engine, and difficulty starting the vehicle.

2. How can I diagnose a faulty alternator?

There are several ways to diagnose a faulty alternator. You can use a multimeter to test the voltage output of the alternator, inspect the belt and connections for any damage, and check the condition of the battery. A professional mechanic can also perform a load test to determine if the alternator is functioning properly.

3. Can I drive my car with a bad alternator?

It is not recommended to drive a car with a bad alternator. The alternator is responsible for charging the battery and powering the electrical components of the vehicle. If the alternator fails completely, the car may stop running and leave you stranded.

4. How can I prevent alternator problems?

Maintaining your vehicle's alternator is key to preventing problems. Regularly checking the belt and connections for any damage, keeping the battery terminals clean, and following the recommended maintenance schedule for your vehicle can help prevent alternator issues.

5. Can I replace the alternator myself?

Replacing an alternator can be a complex and difficult task. It requires knowledge of the electrical system and specialized tools. It is recommended to have a professional mechanic replace the alternator for the best results.

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