ALTERNATOR ON CAR TESTING
Today in practical we did alternator on car testing. WE started by carrying out some visual checks first be we started any testing as this is safe and will give a good and accurate reading. We checked that there were proper connections and that nothing was loose. After this we carried out a no load test with none of the accessories on and engine running at about 1500 rpm. We recorded the battery's ocv which was 12.3, after that we checked the regulator voltage reading which gave us a reading of 12.3 which is below the spec range of 14.5 and 14.6. The last test on no load was the output amps test. We did this by putting a clamp meter through battery wire which goes to the alternator, we got a reading of 0.2 which well below the spec of 5 and 12. This reading can vary due to the state of charge of the battery and the current needed to run the engine. After break we came back and prem had bring the carbon pile so that we can use it to put a load on the alternator. we did the output amps check again but when it was under load we got a reading of 29.1 Amps And the charging voltage under load to be 12 Volts. These test's show us that the alternator is correctly charging the battery when there is a load put on, it is out putting the right amount of current and that the alternator is able to hold the load. If for example the alternator was out putting less amps it would mean the the battery would be getting drained and that the alternator is at fault and not working properly. The last test we did was a voltage drop test, first was from the battery to the alternator we got 0.17 which is a pass and it needed to be under .2 volts. This just tell's us that there is no extra voltage being used up some where. We also did a voltage drop test between battery negative and alternator body to check if there was any loss of volts in the grounding of circuit.
ALTERNATOR OFF CAR TESTING
Today in practical we got to dismantle an alternator and check the different components of it. First we took the rear cover off and the regulator and the brush holder on the alternator. The first test we diid was the rotor winding to ground test i place the black lead of the meter to the rotor shaft and the red lead on the slip rings. I got a reading of infinity this is because there is no circuit between the shaft and slip ring. If i did get a reading it would have meant that the rotor winding has been shortened to ground and should be replaced. After that we did the rotor winding internal resistance test and we got a reading of 3.1 ohms. This meant that there is a circuit between the slip rings. After that i removed the rectifier and the housing. Then we tested the stator winding to ground test and we got a reading of infinity this is because there should be no circuit between the circuit and ground. We then tested the voltage regulator, the short circuit light was off signaling no short circuit. The warning light came on and stayed on as well as the field light continuously flashing meaning we had wired it up properly. We got a set point voltage spec of 14.5 meaning the output voltage will not exceed this in controlling the strength of the magnetic field. The last check we did was checking the length of the brushes. The minimum requirement of the length of brushes was 4.0mm, we got 8mm which meant the brushes had constant contact with the slip rings so that it can supply electricity efficiently.
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