CHARGING SYSTEM

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.

Circuits

Today we did Electricity Circuits individual,Series,And parallel Circuits in practical class. I created a Series circuit on the boards using a battery source,a light bulb switch and wires. I measured the available voltage using a voltmeter..What i found was that as the voltage passes through the different components the voltage starts to drop slightly..the most voltage drop occured at the terminal after the light bulb and at the negative of 12v supply.this is because the bulb is the consumer it uses the most volts..



Terms I Learnt:


Available Voltage:
Is voltage that is available for a consumer to use...We can use a multi meter to do this, by putting black lead from multi meter to ground and red lead to point where we want to measure.

Voltage Drop:
Is how much voltage has been taken by each components (consumers) in a circuit. We use a multi meter and by placing both leads on either side of component.

Series Circuit: Is a circuit with 1 conducting pathway

Parallel Circuit: Is a circuit with 2 or more conducting pathways

Compound Circuit: Circuit which within is a combination of both series and parallel circuits. 

In a series circuit, the voltage is shared between all components, the amps remain the same throughout the circuit. The total voltage is the sum of the voltage through each component.

In a parallel circuit voltage remains the same at each component.but amps are shared through each component. Thus the total current is the sum of the currents through each component.

I learnt how to calculate resistance of light bulb using ohms law by using volts,amps,and resistance...we need to of these to calculate the third part of equation..i also learnt the power law for calculating watts used at light bulbs..we went on carrying out the practical on differen sizes of light bulbs and connecting them in parallel and series which gave us different readings...Experimenting with series and parallel circuits and interpreting the readings we got gave me a clear understanding on voltage drops and current flow in different circuits..