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PAGES HOW THE ALTERNATOR WORKS! To understand this we first have to understand the theory behind generating electricity. This is simple and should take you back to your school-days! I will keep it as simple as I can. If a copper conductor is passed through a magnetic field it causes electricity to flow in the conductor. In the alternator the copper conductor is represented by many coils of copper arranged as the fixed stator that is mounted around the inner side of the case. The magnet in a modern alternator is once again coils of copper arranged as the rotor, the part that rotates inside the alternator and is connected to the pulley via the shaft. If we connect a DC voltage to the rotor coils the rotor then becomes an electro-magnet, its power being determined by the voltage applied to it. when we rotate the rotor we induce the magnetic field into the Stator coils and , hey- presto! we have our electricity! Its not that simple! Because of the rotating magnetic field we produce the direction that the current flows in the stator coils alternates (reverses) constantly. This is called Alternating current (AC) and is useless for our needs! We have to condition the AC to give a simulated DC (Direct Current). We use a simple semi conductor device called the Diode to do this, the diode is like a one way valve That only allows current to pass it in one direction, we call this rectification. We now have the DC voltage appearing at the outputs of the diodes but another problem! It will change its value and increase with the speed that the rotor (and engine) is rotating. No good for our 12 volt boat! Remember I said the magnet in the alternator is an electro-magnet? and that its strength is dependant on the voltage applied to its coils? Well we can use this to set the output of the alternator to any voltage we require, in practice we constantly vary this rotor voltage to give us a stable dc output. This is under the control of the regulator pack! This little electronic device constantly measures the voltage at the output of the alternator or the battery posts and then varies the voltage to the rotor to constantly vary the magnetic field the rotor produces. It can be explained simply by looking at the way we drive a car! Lets say we are cruising on the M25 at 70 mph (in my dreams!) The car is traveling up and down hills all the time so the power needed to the wheels to keep us at 70 mph is constantly changing, The driver acts as the regulator, constantly monitoring the engine speed by looking at the speedometer. As the speed drops the driver increases the pressure on the accelerator peddle, as the speed rises he decreases the pressure on the peddle. He is regulating the engine speed in the same way the regulator in the alternator regulates the output voltage. This rotor voltage is what the alternator controller uses to control the alternator output. the controller bypasses the internal regulator. The regulator also provides a control signal to an indicator to show us when the alternator is actually working, and this connection is also used to turn the alternator on when we start the engine. Some boats need another connection to the alternator, this is made to the output of the stator before the diodes This voltage is not rectified and so is AC. We feed this into another electrical circuit inside the rev-counter Tat actually counts the number of cycles (revolutions) of the alternator and uses this information to display the engine speed! If you understand any of this please let me know! I have been asked to write some pages on how things work! I am technically inclined so it all seems simple to me! If you can understand what I am trying to put over I will carry on, if not I wont waste my time!
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This site is published with the sole intention of providing information. The authors take no responsibility for any damage to yourself or your possessions whatsoever, caused by the misuse of this information .
Compiled using Microsoft FrontPage 2000 MARCH 2001
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POWER! 