AC motors (asynchronous motors) and DC motors (synchronous motors) are two very popular models of electric motors, but what sets them apart?
Here is a comparison of AC motors and DC motors to help you better understand and distinguish between them.
An AC motor operates on alternating current. Alternating current flows in one direction and then the other. It is measured in hertz (Hz), representing the number of changes in current direction per second. AC is commonly used for electricity distribution due to its limited intensity and reduced heat loss compared to direct current.
A DC motor is powered by direct current. Direct current flows in only one direction (from the negative pole to the positive pole) and is generated by a source such as a battery, cell, or photovoltaic solar panels. It is occasionally used for electricity transmission but typically over very long distances.
The speed variation
Varied speed control of an electric motor is essential for certain domestic or industrial processes. However, the speed of motors is mostly constant in the majority of cases. Speed variation becomes interesting to transform the operation of the motor and the driven machine.
The rotational speed of a motor allows the conversion of electrical energy into mechanical motion. It depends on the motor’s construction, the type of power supply, and slip.
There are 3 techniques to vary the speed of an asynchronous electric motor:
- Increasing or decreasing the number of pole pairs (during construction);
- Adjusting the frequency of the power supply;
- Manipulating the slip of the motor (for slip-ring motors).
To vary the frequency of an AC electric motor, there are several solutions, but the most common and straightforward method is to adjust the supply frequency using a frequency converter. AC motors are preferably used in cases where speed variability does not require high precision. They are perfect for constant speed applications with minimal speed changes.
For a DC motor, it’s the variation in voltage that will modify the motor’s rotational speed. Speed variation is achievable here without additional equipment and very precisely.
Le moteur AC, conรงu pour un usage intensif
The AC motor is a robust motor with a long lifespan, requiring minimal maintenance and offering an excellent cost-to-performance ratio. It is also energy-efficient.
The DC motor, a high-precision motor
The DC motor is a precise and fast-responsive motor (quick start/stop/acceleration). Additionally, it is perfect for applications requiring a high starting torque.
No three-phase motor for the DC motor
The DC motor is available only in single-phase, whereas the AC motor can be found in both single-phase and three-phase configurations. Today, DC motors are fading in favor of AC motors with frequency inverters. DC motor parts are indeed expensive and hard to find, while AC motors are offered at a more affordable price and require minimal maintenance.
