4841 Alternators & Batteries

Alternators

Rotor windings

This week in class we started new subject alternators. First we had to disassemble it and carry out a test on rotor winding to ground test. To carry out these test all u need it a Multimeter, we had to set the Multimeter on 2k and place the positive lead on the rotor shaft and the negative lead on the slip rings and the reading should be infinity, if we get a reading that means that the rotor windings is shorted to the ground and we need to replace. After this this test we carried a test on internal resistance (slip rings) and according to the specs we need to within 2-6 ohms.

Stator windings

The next test we carried out was on the stator windings to carry out this test we had to place the negative lead on the common point (the one with most wires) and the positive lead on the other winding terminals, to meet the specs we had to get a reading between 0.0-.2 ohms the readings we got was 0.00 so we were within the specs. After the test we had to carry out a ground test for this we did set the Multimeter on 2k place the positive lead on the common terminal and the negative on an alternator body, to meet the specs we had to get a reading infinity if there was a circuit the stator has grounded and needed to replace. The readings we got was infinity and we were within the specs.

Rectifier positive & negative diodes.

The rectifier is the part that coverts the ac current to dc current, for the rectifier to meet the specs, out of four terminals the three terminals should show high resistance and one terminal to show infinity.

Voltage regulator

To test the voltage regulator we had to use a Transpo regulator tester, by using the information chart we had to set the tester on 12 volts and field current to 0.5 amps and had to connect the leads according to the diagram of the regulator. To meet the specs we had to get a reading of 14.6 volts.

It is used in alternator to maintain a constant level of voltage to the battery when required.                                                                                                            

The next day in class we had to do an assessment on car similar to what we did in the class.

Batteries

The last day of this week we got introduced to batteries the first thing we had to do was a visual check on the company, model no and cc rating. Then another visual check we had to do was on loose connections, corrosion, cut or any damaged wires and leaking on the batteries. After that we had to check the electrolyte levels and we did an open circuit voltage test and then find out the state of charge. Then we carried out a electrolyte specific gravity test and refill the battery if the water is low, record the readings on each cell and the colour of water in it (murky or clear). We finished of the day by carrying a load test on the battery using a load tester.

Safety

In the first theory class Ian went over the safety hazards & safety precautions while working in the workshop.  The main safety precaution while in a work shop is to always wear safety boots and an overall at all times. When the safety precautions are not followed in the workshop can lead to serious injuries and may lead to death.

4841 Electrical Blog

Circuits

In the first practical class Prem handed us a booklet and went over the book briefly what is going to be covered in circuits.

•  Series Circuit
• Parallel Circuit
• Compound Circuit

Series Circuit

Unitec provides us with a premade circuit board we create circuits on them using the 12 volts supply.

We started making a series circuit with one bulb (smaller Bulb) using a control switch and a 10 amp fuse. We slowly made our way through using 2 bulbs (2 larger bulbs) with a control switch and a 10 amp fuse.  We finished off series circuit by using 3 bulbs using a control switch and 10 amp fuse.

While we were doing the circuits we had to get the readings with multimeter and fill in the practical book we detailed explanations.

In a series circuit the current (amps) will be the same but the voltage is different, that is why the bulbs are not brighter in a series 

circuit.

Parallel Circuit

We made a parallel circuit on the same circuit board as earlier.

The first parallel circuit consists of 2 larger bulbs and a control switch and 10 amp fuse. And followed by we did a circuit this time use used all three bulbs and a control switch and a 10 amp fuse. 

All the circuits we made on a parallel circuit all the bulbs were brighter because of the same voltage going through the each bulb.

Compound Circuit

When a parallel and a series circuit are made together it is called compound circuit.

We made a compound circuit with 3 bulbs and 2 of the bulbs are connected in  parallel and the other 1 is connected in series. It is controlled with a switch and consists a 10 amp fuse. In a compound circuit the parallel bulbs are dim and the series bulbs are brighter.

Fuels

TPS Sensor

Cold – AC Volt 0.3mv

Crank – AV Volt 0.3mv

Idle – AC Volt 0.4mv

Rev – AC Volt 5.6 mv

Tps sensor measures the throttle position in an internal combustion chamber. We did some tests to found out how much mv was putting out. When it is cold it was putting out 0.3mv (av) when we cranked the engine it was still putting out 0.3mv when the engine was idling at a normal temperature it was 0.4mv when we rev the engine it was at the  highest volt 5.6mv. All the reading will be sent to the ecu and the ecu process it and it will adjust the engine and the fuel injection timing.

Knock Sensor

Cold – 0.277 HZ

Crank – 6.35 HZ

Idle – 5.55 HZ

Rev – 12.7 HZ

Knock sensor is listing device which is located by the intake manifold. We did some test to find out to see how the frequency differs in different scenarios when the engine was cold it was 0.277HZ and when we cranked the engine it was 6.35 HZ and when the engine was idling at a normal temperature it was 5.55 HZ and when we rev the engine it was at its highest 12.7 Hz. All this information is sent to the ecu and ecu process it and it adjust the engine timing. The engine knocking is also known as pining.

Closed loop fuel control

The closed loop fuel system determines how hc, co and nox leaves the tail pipe. The closed loop system works during normal idle and cruise operations and makes adjustments to the fuel injection based on the signals from the oxygen system.

During closed loop operation the air / fuel mixture is 14:7 to 1 air/fuel ratio (stoichiometry).