Generator Alternator electrical repair

Here is the video covering all these details in motion.

House hold generator or alternator is a machine which runs using fuel like gasoline or methane gas and producing line electricity to run electrical appliances like lights, motors and other house hold equipment. The generators are great machines to produce emergency electricity. They work very nicely if they are in their service life. They produce very clean and nice quality electricity suiting to most house hold needs. These machines are very reliable as long as they are good maintained.  An alternator consists of engine and generator or dynamo part. The engine is known as prime mover and running the generator to produce electricity. The dynamo or generator part is electrical part and is producing electricity which is further used.

The alternator or generator has same like synchronous motor construction. It has two major parts like stater or armature and rotor or field. These two parts have winding on them. The stater or armature is producing electricity and the rotor or field winding is producing magnetic field which is necessary to produce electricity. The rotor or field winding is supplied power through slip rings. The slip rings have carbon brushes touches to them and they are providing power all the time to field winding. The field current is known as excitation also.

The carbon brushes are connected to AVR automatic voltage regulator. The AVR is an electronic circuit which is regulating the output AC voltage of the generator produced. AVR is monitoring the generator voltage all the time and regulating it to a certain value. The regulation is achieved by controlling the field current. The field current is directly proportional to the alternator produced emf. So this is actually a closed loop which is monitoring the output all the time and based on output voltage the AVR is controlling the field current to achieve regulated output voltage or line voltage. The AVR output can be adjusted through a potentionmeter or variable resistor to get the appropriate output voltage. That variable resistor is located on the AVR body. One can adjust it using a screw driver.

The wiring to the AVR and from the AVR to the carbon brushes should be firmed and tight. If there will be any loose connection or bad contact in the wiring, the output will be badly effected. Here in the following screens I am showing a problem which occurred in a generator due to loose connection and also demonstrating the output voltage adjustment through AVR. 

There is no out put on the generator output voltmeter. Or zero output voltage when the generator had been started and is running at its normal speed.

No output voltage at alternator output volt meter read out and output power socket.

The generator is only producing output voltage when its wiring is wiggled. The output voltage produced is not 220V but less as 165V.

The generator wiring having some problem as it only produces voltage when wiggled.

The following image is showing the output voltage when the generator wiring is wiggled.

The generator is only generating voltage when its wiring harness is wiggled and is pressed.

To diagnose this problem it is required to open the end cover of the alternator where its wiring and connection is located. This cover is held by two screws. Both screws are needed to be removed using appropriate screw driver.

Unscrew both screws to remove the generator end cover. Under this cover generator connections are located.

After opening the end cover keep it side and look at the wiring connections and wiring. Make a visual inspection for any abnormality and damage.

Under the end cover check the wiring and all connections for any damage.

I found an earth or ground wire Yellow and Green loose in its thimble. I found it loose when wiggling on this wire. Removed it and soldered it in its thimble to avoid any loose connection in future.

check for any abnormality, I found this wire loose in its thimble.

Open the screw for carbon brush holder to remove the brush assembly. Check and inspect it for worn out and any damage. Replace if needed. In my case it only needs a little cleaning. Also inspect the slip rings underneath. Clean them using cloth and sand paper if needed.

Alternator carbon brush holder inspection. Inspect for any damage and worn out carbon brush.

Unscrew all screws for AVR to bring it off the generator. Secure all the screw for fixing them back in the end.

Remove the AVR screws to bring it off.

Look at the AVR. You will find a variable resistance or potentiometer to adjust the out put voltage. Adjust this variable to adjust the output voltage using a small screw driver.

Locate the variable resistance of potentiometer on the AVR for output voltage adjustment.

Inspect the circuit board for the AVR for any damage. Repair if you find any loose connection on the board. In my case it was perfect.

Inspected AVR circuit and check it for any damage. Repair if needed.

Now start the generator to adjust output voltage. Be very much careful as you are dealing with 220V AC power. It is lethal and can kill. Don't touch any open wire or connection.

Adjust the output voltage of the alternator by adjusting the potentiometer on AVR using a small screw driver. Keep an eye on the output meter and adjust the potentionmeter till you set it to the desired 220V.

Stop adjustment and fix every thing back when you get the desired 220 V or 230 V output on the generator output panel meter. Use the generator then for your regular use.