AC generator and DC generator
Most commercial machines and equipment is AC generator. However, commercial DC generator are commonly founded in electromagnetic applications. Some are used in Traction applications like subways and trains. Some DC motor-generator sets provide the field currents for large commercial power Alternators/ AC generators as in hydro-electric dams.
Generator working principle: Generator works by moving electrical conductors through a magnetic field. If your generator doesn’t have magnets, it won’t produce electricity. The magnetic field is created by taking some of the generator output voltage and converting it to DC and feeding it to a coil to make an electro magnet. In other words, the process of converting energy is performed by electromagnetic induction. There are also two types of generators and these produce currents that differ in terms of the manner in which they move.
All electrical generators whether AC or DC, depend upon principle of magnetic induction regardless of their size. In a DC generator, the armature is always the rotor. In alternators, the armature may be either the rotor or stator.
Although both generators produce current using the same process, they have different design, mechanisms, uses, output connection and types.
First - design differences
As mentioned before, both AC and DC generators produce currents via electromagnetic induction. In AC generators, the coil through which the current flows is fixed, and the magnet is moving. The magnet’s north and south poles cause the current to flow in opposite directions, producing an alternating current. With DC generators, the coil through which the current flows rotates in a fixed field. The two ends of the coil attach to a commutator: different halves of a single, rotating split ring. Metal brushes connect these split rings to an external circuit. The commutator balances the charges leaving and returning to the generator, resulting in a current that does not change direction.
Please know that both AC and DC generators follow electromagnetic principles, yet these two machines have difference means of collecting and transferring induced electromotive forces in the external circuit. Since the connection of external circuit and armature varies with these two types of generators, this explains the difference in how electromotive forces are collected and transferred.
AC generators have two commutators while DC generators have only one. The slip ring contains two semi-circular metal rings. These rings are insulated from one another. AC generators produce an output voltage called alternators. On the other hand, DC generators produce a steady output voltage.
Third - Primary Uses of AC and DC Generators
AC and DC generators serve different uses. AC generators are used to power small motors and common electrical appliances at home. These appliances that can be operated using AC generators include vacuum cleaners, food mixers, juicers and electrical fixtures. However, DC generators are functional in supplying power to large electric motors — such as those needed for subway systems. Moreover, DC generators provide a reliable and efficient energy supply that can charge banks of batteries used for mobile and off-grid uses.
Fourth - Output connections
In the alternator used in AC generator, the generated AC is brought to the load unchanged by means of slip rings.
In the DC generator, the emf generated in the armature windings is converted from AC to DC by means of the commutator.
Types of AC generators are rotating armature alternator and rotating field alternator. Single phase AC generator produces 25 KW or less. Single phase generates power at specific voltage. Polyphase generates two or more AC voltages usually two, three or six phases.
