I. Dismantling:
Normally, i have to dismount an alternator from the car first. That means i have to remove the driving belt, unscrew the mountings, make sure I don't damage anything on my way of taking it out. There is one big notice that we all have to make, that it is dependent on the construction of each car to determine the difficulty of dismounting its alternator, so I make a note of that.
But in this off-car assessment, we were provided a dismounted alternator, so the main thing is i just have to make sure i follow the instruction to dismantle the alternator correctly part-by-part.
II. Testing (I have to make sure i follow the instruction carefully because there are numberous tests with flipping, easily mistaking contents). Before every resistance test, internal resistance of meter is always accounted for.
1. Rotor windings:
a. Rotor winding to ground test:
The slip rings are hooked on the shaft to guaranty its spinning motion when the alternator is being driven. The brushes are the slip rings electrical contact to bring in-and-out the current from the battery. So it is very important that the slip rings are fully insultated with the shaft because we don't want any short-to-ground during the operation which can potentially damage the circuit. By carrying out the test i can understand more about the importance of correct wiring.
b. Rotor winding internal resistance test
Specification of the circuit between the 2 slip rings is 2-6 Ohms, to ensure there is a strong but not overheating conduction. Lower than 2 Ohms, possible overheating when current passing through is too high is anticipated. Resistance too high, power generated may not catch up with load applied on the battery.
2.Stator windings.
Similar to rotor windings in the concept of induced voltage, stator windings is a force-multiplier. More coils means more voltage is induced. Therefore the resistance quality of the stator coil must be minimized from 0 to 0.2 Ohms, to ensure most efficient ducting and prevents too big of a current. So in order to check this, we had to touch the black lead to the common point, and the other open terminal to red lead consequently, and record the readings.
Again, stator windings to ground must be absolutely zero, which means it reads infinity on resistance. Grounding is fatal, unacceptable, operation-jeopardizing so if there is any readable value means that there is a circuit exists, we will have to check and replace the stator wirings.
3. Rectifier
The rectifier component of an alternator is truly "where the miracle happens". By using phase rectification diodes, it successfully converts the alternating current into a one positively directied DC current, no matter what way the AC is going. Testing this componet can be confusing, so I put it this way NOT to be confusing:
a. Anode test:
P-inputs
(Direction of positive diode current)
The AC current generated goes through Ps to be converted and continues to output B. This mean when tesing: common lead on B, red lead on Ps, we will get a low resistance readings (i.e 0.5 to 0.7 VD) . If we do the opposite, the resistances must be infinite, because reversing current is completely prevented by diodes.
b. Cathode test:
Let say P is inputs, E stands for Earth is output. Because there isn't supposed to be any outcome to E, the reading must read "infinity".
On the opposite, since these are diodes, it is reasonable for the opposite test to have low resistance readings( i.e 0.5-0.7 VD)
So this being said: preventing current to go to ground is essential as the function of the rectifier being rectified by this practical test. For example, one of our readings were Infinity for the reverse test of the negative diodes test, this means a negative diode is deflected and it is reasonalbe to replace the whole rectifier.
4. Voltage Regulator
The next piece of the puzzle, now to make sure the amplitude of the current generated does not damage the circuit when various applications apply to the performance of the rotor's speed, especially when reving @ high rpm. It's circuitry (of combination of BJTs, reostats, resistors and diodes) brings back a regulated voltage that is safe for the circuit.
While testing, faults from the rectifier or anywhere that inputs the regulator can jeopardize its test result. So before we deem the regulator to be faulty, we must have accounted for the fore-operations. This our case, a negative diode from the rectifier is faulty, then this alters the test result of the regulator on a Transpo Tester. This could be the short circuit light didn't turn off during testing or turn-off of the tester. The field light didn't flash as rapidly .etc...
5. Brushes and Bearings:
Make sure these are in contact with the slip rings, so protrusion length is essential to test( ie. minium 4mm long)
Bearings are components those operate under high friction and compression conditions, they are the kevlar for rotating operation of the alternator. So it is being said, replace them regularly.
So by carrying out the alternator dismantling test, we really have a deeper look into the operation of the alternator. We now understand more about its role in the charging system, along with all inputs and outcomes aspect about it. ANYWAY, IF UR ALTERNATOR F*** UP, THROW THAT DEAD WEIGHT AWAY AND BUY A NEW ONE, IF WE'RE TALKING ABOUT TURBOS AND STUFFS!!!
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