The different types of electric motors: how to choose?

DC motors are widely used in industrial applications. Their basic principle is based on the presence of a permanent magnet or an electromagnet that generates a fixed or variable magnetic field. This magnetic field acts on nearby electric conductors, called coils or armature windings. The armature windings are mounted on the rotor (rotating part) of the motor.

These motors offer several advantages, including:

• Precise speed and torque control

• High torque at low speeds, making them an ideal choice for applications requiring frequent maneuvers

• Adaptability to battery voltage

However, they also have some disadvantages:

• Higher cost compared to asynchronous motors

• More advanced control system required to manage current switching

Synchronous motors are electric motors in which the rotational speed is directly proportional to the frequency of the power supply. 

In synchronous motors, the stator contains copper coils that are supplied with three-phase AC current, creating a rotating magnetic field. The rotor is equipped with a set of permanent magnets or an excitation winding that generates another magnetic field. When AC current is applied to the stator, the rotating magnetic field induces a magnetic field in the rotor. The two magnetic fields interact, creating a rotational torque that rotates the rotor at a speed equal to the frequency of the power supply.

These motors offer several advantages, including:

• High efficiency

• Fast dynamic response allowing precise propulsion control

• Constant torque at specific rotational speeds

However, synchronous motors also have some disadvantages:

• Control complexity requiring more complex control systems and a frequency converter to adjust the rotational speed

• Higher cost

Asynchronous motors, also known as induction motors, are the most commonly used electric motors due to their relatively low cost and simple design. 

In asynchronous motors, the rotor consists of copper bars or short-circuited windings. Unlike synchronous motors, the rotational speed of the rotor is not synchronized with the frequency of the power supply.

These motors offer several advantages, including:

• Affordable cost

• Simple control that does not require a frequency converter to adjust the rotational speed

However, asynchronous motors also have some limitations, such as decreased torque at low speeds.