An AC generator refers to an electric generator used to convert energy from mechanical to electrical by using alternating current or alternating EMF, while a DC generator converts mechanical energy into Direct Current or DC.

Direction of current

With AC Generator, the AC alternator directs the electrical current periodically in the reverse direction, which is why it’s called the AC alternator generator.

In contrast, the DC alternator will only allow the electric current to flow in one direction, known as the direct current alternator.

Design

The coil where the AC current flows is fixed with the AC generator, but the magnet is movable. This is a simple and less costly construction.

With the DC generator, the coil used for the electric flow rotates in a fixed field. Overall the design is pretty simple, but the construction is not as simple, especially for the slip rings and commutators.

Commutators and Rings

These are used for both the AC and DC current.

The AC generator does not have commutators, while the DC generators do. Both have slip-rings.

Brush efficiency

With AC generators, the slip rings have an uninterrupted and smooth surface which means they do not wear out too quickly, making them highly efficient. Still, in DC generators, the commutators and brushes wear out quicker and hence less effectively.

Short circuit risks

With AC generators’ highly efficient brushes, there is a less likely risk of short circuits. In contrast, the DC generators, whose commutators and brushes wear out too quickly, have a higher chance of short-circuiting.

Current induction

The AC generator’s AC current can be induced through the rotor or stator, while the current is only induced using the rotor for the DC generator.

Maintenance

AC generators need very little maintenance making them highly reliable, but DC generators frequently need maintenance, making them less reliable.

Cost

The cost of AC generators is initially high, but due to the less maintenance cost, it doesn’t add up as much; but the DC generators are less costly, but with the high maintenance cost, this actually makes them more expensive with time.

Transmission distribution

The AC generators can efficiently distribute the AC current easily through the transformer. Still, the DC generators have a hard time distributing as the transformers cannot be used in this case.

Efficiency

AC generators are pretty efficient and have a lower energy cost. In contrast, DC generators are less efficient as they constantly have sparks and losses in terms of eddy current, copper, hysteresis, and mechanical.

Application areas

AC generators can be used in powering electrical appliances at home such as vacuum cleaners, mixers, etc., and they can also be used to power small motors. In contrast, the DC generators can only be used in powering huge electric motors such as those needed on subway systems.