Introduction
Generators and alternators are widely used devices in electrical systems.
If you drive a car, you’ll likely be more familiar with the alternator under the hood. Generators of different sizes are also often seen in household and industrial applications.
But despite their popularity, there is slight confusion as to their differences. Or are there any differences at all?
This guide will unplug the nuanced comparison of alternator and generator.
What is an Alternator?
This energy conversion device turns mechanical energy into Alternating Current (AC).
Alternators are often found under cars’ hoods. They recharge the car battery and help power other devices.
When the engine turns on, the crankshaft rotates. A serpentine belt attached to the crankshaft pulley rotates the alternator rotor. When the rotor shaft turns, it spins the powerful magnets inside to generate AC.
However, the alternator must charge the battery, and an AC output cannot. The rectifier, a one-way diode or valve that converts AC into DC, must first convert the AC into direct current.
You can classify alternators into different types based on design and application. Car alternators are but one type. But all kinds rely on the same principle of energy conversion. Here is a comprehensive guide to choosing an alternator.
What is a Generator?
Like alternators, generators turn mechanical energy into electrical energy. The critical difference is that generators convert the energy into AC or direct current (DC).
However, a generator producing AC output will have a moving magnetic field. By this definition, an alternator can be an AC generator subtype. Only DC generators have a spinning armature and a fixed magnetic field.
A generator converts power to DC through a commutator. This component serves as a mechanical rectifier. The commutator changes the current’s direction from the rotor to the circuit.
Build-wise, generators are relatively larger than alternators. They’re often used in power stations and as backup power supplies.
Difference between Alternator and Generator
This simplified chart should give you a comprehensive contrast between the two.
| Aspect | Alternator | Generator |
| Function | Turn mechanical energy into electrical in the form of Alternating Current (AC). | Turn mechanical energy into electrical as AC or direct current (DC). |
| Output Current | An alternator always produces AC only. | A generator can deliver output current either as AC or DC. |
| Magnetic Field | The magnetic field moves inside the stator. | A DC generator has a stationary magnetic field while the armature is moving. |
| Armature Movement | An alternator has a stationary armature. | A generator has a moving armature. |
| Voltage Generation | Only produces voltage as needed. | Constantly produces voltage. |
| Input Supply | Alternators take input from the stator. | Generators take input supply from the rotor. |
| Voltage Control | Better with voltage regulation. | Have difficulties in voltage regulation. |
| Phases of Voltage | Alternators generate three-phase AC. | Depending on the design, a generator produces multi-phase or single-phase DC. |
| Cooling Type | Most often air-cooled. | Either air or liquid-cooled. |
| Size | Alternators are smaller in build size. | Generators are generally bigger and occupy ample space. |
| Energy Conservation and Efficiency | Alternators conserve more energy and are more efficient. | Generators conserve less energy and are less efficient. |
| Polarization | Alternators do not need polarization after installation. | Generators need polarization after installation. |
| RPM range | Alternators have a wider RPM range. | A generator has a low RPM range. |
| Lifespan and Maintenance | Alternators have longer lifespans and do not need high maintenance. | Generators have a shorter life and need high and regular maintenance. |
| Cost | More cost-effective. | Potentially more expensive due to added components and higher maintenance. |
| Applications | Alternators are most common in the automotive industry to power and charge car batteries. | Generators are used in households and more significant industrial applications. |
FAQs
1. Can alternators and generators be used interchangeably in vehicles?
Generators and alternators are not inter-compatible when used in cars. While they’re similar in purpose, they have distinct functions and performance.
Generators were initially used in automobiles until the 1960s. Before, cars relied on direct current dynamo generators. But modern vehicles have switched to alternators for better performance and efficiency.
While older models rely on generators, they can still upgrade to alternators. But, newer models cannot downgrade to generators. Such devices are not ideal for keeping up with power-hungry car components.
2. What are the advantages of parallel alternators?
A parallel circuit operation ensures constant voltages while dividing the current. Constant voltage guarantees effective and efficient power system operation.
The inherent advantages of a parallel alternator operation include increased load supply. Combining the power ratings of parallel alternators sums up the individual machine ratings. This exceeds the supply of an individual alternator, allowing for higher capacity.
Another advantage comes from a reliable operation. Parallel operation ensures the system continues working even if one alternator fails. The remaining alternators will continue to deliver power, thereby increasing system reliability.
Additionally, parallel alternators allow for enhanced efficiency. Multiple alternators are better and more ideal for load management. This condition guarantees minimal operation costs, which is relative to improved efficiency.
3. What are the losses in a generator?
Not all current produced by a generator will serve a purpose. Some of the current will be lost in the process in the form of dissipated heat. Here are the most common losses in generators.
- Copper losses
Copper loss is the heat dissipation from copper windings. This power loss is due to the wire resistance in primary and secondary windings. Using wires with sizeable cross-sectional areas can help reduce copper losses.
- Eddy current loses
Eddy currents are currents circulating within the core. They are electrical current loops within conductors prompted by a changing magnetic field. Using laminated steel for the armature and cores can maintain eddy current loss at a low value.
The lamination of steel sheets insulates each sheet from one another. This ensures the current will not jump from one sheet to another.
- Mechanical losses
Mechanical loss is induced by the air turbulence caused by armature rotation, called windage. It can also be induced by commutator brush friction and bearing friction. Strict maintenance can reduce mechanical loss. Friction will be minimal if the bearings are clean and lubricated.
- Hysteresis losses
Hysteresis loss is energy loss relative to the delay in magnetization and demagnetization. Heat-treated silicon steel can minimize this slight energy loss.
4. Which is easier to maintain?
Alternators have fewer moving parts than generators. In this case, the alternator has lower maintenance than generators. Check out the replacement cost of your alternator.
Generators’ additional components wear faster, requiring constant maintenance. Generator brushes are also less efficient and have a shorter lifespan. These conditions also contribute to the higher costs of owning a generator.
But this is not to say that generators are not reliable. They are dependable power systems that can still last between 20 and 25 years with proper and regular maintenance.