AC & DC Generators - What's the Difference?

    (Provided by Steven Nameroff - Friday, August 19, 2016)

AC and DC Generators

AC and DC generators generate electric current through electromagnetic induction. Electromagnetic induction occurs when an electric current passes through a shifting magnetic field, which allows mechanical energy to be converted into electrical energy.

One of the key differences between an AC and DC generator is that in the former, the electrical current reverses direction occasionally, while in the latter, electric current flows progressively in one direction. Below are several other differences.

Basic Uses & Design

AC and DC generators serve different primary purposes. This is especially evident in the type of devices they each power. Typically, AC generators power home electrical appliances and small motors such as juicers, vacuum cleaners, and food mixers.

However, DC generators are used to power large electric motors such as those used in subway systems.  Batteries used for off-grids are also charged using direct current generators because they provide efficient and reliable energy supply.

In an AC generator, the coil through which current flows is fixed and the magnet usually moves. The south and north poles of the magnet make the current flow in opposite directions, thereby creating an alternating current.

In contrast, the coil in a DC generator is not fixed; rather it rotates in a fixed field. The two ends of the coil are attached to the commutator, which balances the charges to and from the generator, thus resulting in a current that does not alter direction.

Commercial Power Generators

Output Voltage & Safety

The output voltage produced by an AC generator varies in time and amplitude. However, in a DC generator, the output power is often steady. It does not vary in time and amplitude because the commutator balances the voltage.

The output power of an AC generator is normally 120 volts and above. This high voltage can sometimes easily result in injury or even death in some cases. On the other hand, a DC generator is typically low voltage. Hence, minimal inspection and certification is required.


The design of a DC generator provides seamless connectivity and efficient power flow because it does not require a transfer switch. However, an AC generator often requires considerable engineering and incurs high expenses to transfer electricity to remote sections of the grid.



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