What is the difference between magneto and a.c generator?what is meant by frequency of alterneting current?


A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current.

Hand-cranked magneto generators were used to provide ringing current in early telephone systems.
Magnetos adapted to produce pulses of high voltage are used in the ignition systems of some gasoline-powered internal combustion engines to provide power to the spark plugs. Use of magnetos for ignition is limited mainly to engines where there is no low-voltage electrical system available, such as lawnmowers and chainsaws. Magnetos have traditionally been used in aviation piston engines even though a low-voltage electrical system is usually available, to keep the ignition system independent of the battery and charging system and to keep the engine running in the event of alternator or battery failure. For redundancy purposes, virtually all piston engine aircraft are fitted with two magneto systems, each supplying power to one of two spark plugs in each cylinder.

Magnetos were rarely used for power generation, although they were for a few specialised uses.

A Generator is a device which converts mechanical energy into electrical energy.

A.C Generator works on the principle of electromagnetic induction (motional emf). In generator an induced emf is produced by rotating a coil in a magnetic field. The flux linking the coil changes continuously hence a continuous fluctuating emf is obtained.

A.C Generator consists of the following parts.
Powerful field magnet with concave poles.
Armature:It is a rectangular coil of large number of turns of wire wound on laminated soft-iron core of high permeability and low hysteresis loss.
Slip rings:The ends of the coil are joined to two separate copper rings fixed on the axle (S1 & S2).
Carbon brushes:Two carbon brushes remain pressed against each of the rings which form the terminals of the external circuit.


The frequency of alternating current depends on the speed of the alternator/generator at the power production station.

In India, its usually 220 Volts at 50 Hz.
In USA, it is 440 Volts at 60 Hz.
So the variation depends on the speed of the alternator at the time of generation and how the phase changes on the wave.

Hence, its possible to change the frequency of AC.

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