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Basic Understanding of a Automobile Alternator

Basic Understanding of a Automobile Alternator


What is an Alternator ?


The alternator is a generator whose purpose is to distribute electricity to the car and recharge the battery. Outside of some hybrid models, all vehicles with a standard internal combustion engine will have an alternator. The alternator is generally mounted to the front of the engine and has a belt running around it.

Basic misconception is that the battery is powering all things electrical components in your car, be it your windshield wipers, headlights or radio. In reality, it’s the car alternator that produces the majority of your vehicle’s electricity. The battery is mainly just used to Crank up the engine and provide power when the engine isn’t running.

The alternator is a critical component of a car’s charging system, so it’s helpful to understand how it operates.


Main Components of the Alternator:

  1. Rotor:  The rotor is the spinning mass inside the alternator that rotates via the pulley and drive belt system. The rotor acts as a spinning electromagnet. Slip Rings. The Slip rings are used as a means of providing direct current and power to the rotor. 








Type of Fault of a Rotor:

  • Overloading: Overloading is caused due to the high current which causes the Rotor winding to heat up
  • Reverse power: This occurs due to the failure of the prime mover and insufficient torque supplied to the alternator.
  • Lack of Power: Can occur when the excitation to the generator is cut off and the Power factor goes to the leading side. This can lead to the failure of the Diodes on the Rotor and pole slipoings.
  • Negative Phase: Can occur is fixed in an unbalanced manner. This results in overheating of the rotor.
  • Over speeding: When the speed of the alternator is above normal, the forces developed in an alternator will be very high and the ends of the Rotor can slip from their position and hit other parts of the alternator.


 2. Stator: The stator is fixed to the body of the alternator, and does not move. As the rotor turns within the stator  windings, the magnetic field of the rotor sweeps through the stator windings, producing an electrical current in the windings. Because of the rotation of the rotor, an alternating current is produced.




Type of Fault of a Stator:

  • Stator winding Fault: Due to overheating of the stator the insulation of the coil will be torn and the system will get short.


 3. Regulator: A voltage regulator is a system designed to automatically  maintain a constant voltage. A voltage regulator may use a simple feed-forward design or may include negative feedback. It may use an electromechanical mechanism, or electronic components.




Type of Fault of a Regulator: 


  • High Voltage Output: If the output voltage is measuring at 16 volts or more, it’s very likely you have a faulty voltage regulator. Too high of a voltage can actually cause damage to various electrical components. Most commonly, the bulbs in your headlights or taillights will prematurely burn out.
  • Occasional Dips in Power: If you have a bad regulator, it may cause many components such as the fuel pump, ignition system, or other parts which require a minimum amount of voltage to not function correctly.
  • Instrument Cluster Doesn’t Work: Like other electrical components, the instrument cluster requires a certain amount of voltage to display all the information you need while driving. A bad voltage regulator may cause it to simply not work or behave erratically.
  • Dimming or Flickering Lights: You’ll usually notice this with your headlights but it can affect your interior lights and even your stereo system. It again points to a current that is not being adequately controlled.
  • Battery is Dead: It might be due to a host of other causes, including forgetting to switch off your lights, a problem with the alternator, or simply an old battery that needs to be replaced. But it could also be because of poorly managed current due to a bad voltage regulator.


4. Rectifier: The Rectifier is used to convert current from alternating current (AC) to direct current (DC) during the charging process. Rotor. The rotor is the spinning mass inside the alternator that rotates via the pulley and drive belt system. The rotor acts as a spinning electromagnet.




Type of Fault of a Rectifier:  

  • One of the most common causes of low or no charging output from the alternator is one or more bad diodes in the back of the alternator. There are three diode pairs (6 total) in the "rectifier" assembly that convert the alternator's alternating current (AC) output to direct current (DC).


5. Pulley: The alternator pulley allows the V-shape or serpentine belt to spin the alternator and is driven by the      engine's accessory drive system. Commonly made from stamped steel or cast aluminium, alternator pulleys are   available in two types.




Type of Fault of a Pulley:  

  • short chirp noise during engine start-up or shut down is most likely caused by a worn overrunning alternator pulley. A worn overrunning alternator pulley often blocks and performs like a solid pulley. This will cause the belt to slip across the pulley surface during belt and alternator speed fluctuations.


For more information, please visit our website for Technical training -  Basic Product Training - Alternator