Alternator (automotive)

[i] After the war, other vehicles with high electrical demands — such as ambulances and radio taxis — could also be fitted with optional alternators.

[1] Alternators were first introduced as standard equipment on a production car by the Chrysler Corporation on the Valiant in 1960, several years ahead of Ford and General Motors.

Since such a magneto system only depended on the engine's motion to generate current, it could even be used when starting a manually cranked engine, provided the crank was pulled sharply, so that the magneto would produce enough current for the coils to make good sparks.

However, the flywheel magneto still powered the ignition, and since models without the starter had no battery, they continued to use magneto-powered lights.

To provide direct current with low ripple, a polyphase winding is used and the pole-pieces of the rotor are shaped (claw-pole).

The claw pole design produces an AC waveform that is more efficiently rectified than a sine wave.

This uses a shaped iron core on the rotor to produce a multi-pole field from a single coil winding.

The coil is mounted axially inside this and field current is supplied by slip rings and carbon brushes.

These alternators have their field and stator windings cooled by axial airflow, produced by an external fan attached to the drive belt pulley.

With two oversized shaft bearings as the only wearing parts, these can provide extremely long and reliable service, even exceeding the engine overhaul intervals.

The drawback of this arrangement is that if the warning lamp burns out or the "exciter" wire is disconnected, no current reaches the field windings and the alternator will not generate power.

[11] This betters very small high-performance permanent magnet alternators, such as those used for bicycle lighting systems, which achieve an efficiency around 60%.

Larger permanent magnet electric machines (that can operate as motors or alternators) can achieve today much higher efficiencies.

Large AC generators used in power stations run at carefully controlled speeds and have no constraints on size or weight.

Hybrid electric vehicles replace the separate alternator and starter motor with one or more combined motor/generator(s) that start the internal combustion engine, provide some or all of the mechanical power to the wheels, and charge a large storage battery.

[13] When more than one motor/generator is present, as in the Hybrid Synergy Drive used in the Toyota Prius and others, one may operate as a generator and feed the other as a motor, providing an electromechanical path for some of the engine power to flow to the wheels.