The key difference between alternator and generator is that an alternator transforms mechanical energy into AC electrical power, while a generator is a mechanical apparatus that converts mechanical energy into either AC or DC electrical power.
What is Alternator?
An alternator is an electromechanical device that transforms mechanical energy into alternating current (AC) electrical energy. It comprises two primary components: the stator, housing the armature winding, and the rotor, which holds the magnetic field winding or poles.
When the rotor rotates, its magnetic field intersects with the armature conductors, generating an electromotive force (emf) in the armature winding. Since the rotor’s magnetic poles (N and S) continually intersect with the armature windings, they induce an alternating emf in the armature.
What is Generator?
A generator is a broad term referring to an electromechanical device that converts mechanical energy into electrical energy. This electrical output can take the form of either alternating current (AC) or direct current (DC).
A generator typically comprises two main components: an armature and a magnetic field system. Electricity is generated through the relative motion between the armature and the magnetic field system.
Depending on the specific type of generator, this may involve a moving (or rotating) magnetic field system with a stationary armature, as seen in synchronous generators, or a moving armature with a stationary field system, as observed in DC generators. Consequently, the type of electricity produced by a generator varies based on its design.
Alternator vs Generator
The primary difference between alternator and generator is given below:
| Aspect | Alternator | Generator |
| Energy Conversion | Converts mechanical energy into AC electrical energy. | Converts mechanical energy into AC or DC electrical energy. |
| Types of Output | Generates Alternating Current (AC) only. | Can generate both Alternating Current (AC) and Direct Current (DC). |
| Rotating Part (Rotor) | The rotor is the magnetic field. | The rotor is the armature. |
| Stationary Part (Stator) | The stator is the armature. | The stator is the surrounding magnetic field. |
| Output Current Source | Output current is taken from the stator. | Output current is taken from the rotor. |
| Output Voltage | Output voltage is lower than a Generator. | Output voltage is higher than an Alternator. |
| Brush Longevity | Brushes last longer due to no rotor friction. | Brushes wear out quickly due to rotor friction. |
| Polarization Requirement | The output voltage is higher than an Alternator. | Requires polarization after installation. |
| RPM Range | Has a wide range of RPM. | Has a low range of RPM. |
| Voltage Stability | Output voltage varies with the load. | Widely used as a backup power supply in various sectors. |
| Battery Charging Capability (Drained) | Cannot charge a completely drained battery (may burn up). | Can be used to charge a completely drained battery. |
| Energy Efficiency | More efficient and conserves energy. | Less efficient and wastes some energy. |
| Size | Smaller in size compared to a Generator. | Larger in size compared to an Alternator. |
| The output voltage remains constant regardless of the load. | Used in vehicles to charge batteries. | No polarization is needed after installation. |