The collapsing magnetic field will then induce an electric current into the coil (Figure 4). If the electric current is switched off, the magnetic field will collapse. When a magnetic field has been created by applying an electric current to a coil of wire, any change in the electric current (increase or decrease in current flow) creates the same change in the magnetic field. Using a collapsing magnetic field to induce an electric current The greater the number of windings in the coil, the greater the induced voltage.The faster the change (or speed of movement) of the magnetic field and the greater the change in the strength of the magnetic field, the greater the induced voltage.There are two main factors that affect how much voltage is induced into the coil: The movement or change in the magnetic field or magnetic flux induces an electric current into the coil wire (Figure 3).įigure 3: A changing or moving magnetic field induces an electric current in a coil This can be demonstrated simply by moving a permanent magnet across a coil. If a coil of wire is exposed to a magnetic field and the magnetic field then changes (or moves), it creates an electric current in the coil of wire. Using a changing magnetic field to induce an electric current There are two main factors that affect the strength of the magnetic field:ġ) Increasing the current being applied to the coil of wire strengthens the magnetic fieldĢ) The higher number of windings in the coil, the stronger the magnetic field. When the electric current is then switched off, the magnetic field will collapse back in towards the coil of wire. Simultaneously, the magnetic field or flux will progressively grow to its maximum strength, and will become stable when the electric current is stable. When the electric current is initially switched on, the current flow rapidly increases to its maximum value. The magnetic field (or, more precisely, magnetic flux) is effectively a store of energy, which can then be converted back into electricity.įigure 2: Creating a magnetic field by flowing electric current through a coil When an electric current flows through an electrical conductor such as a coil of wire, it creates a magnetic field around the coil (Figure 2). To produce the required high voltages, ignition coils make use of the relationships that exist between electricity and magnetism. The Kettering ignition system became virtually the only type of ignition system for mass-produced petrol cars, and stayed that way until electronically switched and controlled ignition systems started to replace mechanical ignition systems during the 1970s and 1980s. These contacts were then connected by spark plug wires to the spark plugs in a sequence that made it possible to distribute the high voltage to the spark plugs in the correct cylinder firing order.įigure 1: The main components of a Kettering ignition system
#How to build a ignition coil driver series#
The Kettering system (Figure 1) used a single ignition coil to produce a high voltage, which was passed to a rotor arm that effectively pointed the voltage to a series of electrical contacts located in the distributor assembly (one contact for each cylinder).
#How to build a ignition coil driver generator#
The battery, a generator and a more complete vehicle electrical system provided a relatively stable electrical supply to the ignition coil. For the first time, he devised an electrical system that powered the starter motor and ignition at the same time. The first coil-based ignition system is credited to the American inventor Charles Kettering, who developed a coil ignition system for a major vehicle manufacturer around 1910/1911. Although ignition systems have certainly evolved over time – in particular incorporating more and more electronics – they still bear the hallmarks of the original coil ignition systems that were introduced more than 100 years ago.
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