What types of electric motors are there?

Ludmilla Dekker | 27. October 2021

For linear axes and handling systems, igus® offers an extensive range of electric motors. Hybrid stepper motors, DC motors and brushless DC motors find their applications in lead screw drives, toothed belts and rack drives. The electric motors complete the range of igus® automation technology. In this way, entire handling systems can be configured in combination with linear axes.

This blog will describe the principle of operation using the DC motor as an example and then explain the different types and their applications.

The principle of operation using the example of a DC motor

Electric motors are electromechanical converters. This means that added electrical power is converted into mechanical power. In most igus® cases, the mechanical energy is accomplished by a shaft.

A simple electric motor consists of a fixed magnetic part, the so-called stator, and the rotating component the rotor. The stator is an immovable permanent magnet firmly connected to the motor housing. Between the poles is the rotor. The rotor is an armature wrapped with enamelled copper wires. Current is supplied to the rotor through the commutator, which consists of two halves of a slip ring insulated from each other. At both ends of the commutator, the sliding contacts are connected to the current source. As soon as the current flows through the rotor coils, the rotor starts to turn. After each half turn, the commutator reverses the polarity of the current. This reverses the magnetic poles of the rotor. The shaft of the motor rotates due to the recurring polarity reversal.

Different types and their applications

igus® offers a wide range of motors. These include stepper motors, DC motors and EC/BLDC motors. These will be explained in more detail below and their areas of application will be dealt with in regards to advantages or disadvantages the motors have.

There are three different types of stepper motors, the permanent magnet stepper motor, the reluctance stepper motor and the combination of both motors, the hybrid stepper motor. The only one igus® offers. This combines the advantages of both motors. The advantages are that the stepper motor can apply a high and full torque at standstill and has an accurate step angle. Furthermore, the stepper motor has a holding torque. The disadvantage of a stepper motor is the high energy requirement, as it always operates at maximum current. However, this can be counteracted by means of a motor control system . Due to a rotary encoder and the close loop, both of which are adapted to the application, only the required current is consumed. The hybrid stepper motor is mainly used in industry for positioning tasks that require precise motion control.

DC motors are simple electric motors that are operated with DC voltages. This means that they can also be operated with simple batteries. DC motors have two terminals, one for positive and one for negative. Therefore, for a different direction of rotation of the shaft of the DC motor, only the connections of the supply line must be swapped.
This allows the DC motors to be used in a wide range of applications. Typical applications are toothbrushes, children’s toys or fans. However, they are also used in cars as drives for the windscreen wipers or the seat adjusters. Furthermore, simple screen adjustments can be implemented in the area of access control. DC motors are also used in furniture construction and caravans to adjust TV sets.
DC motors are cost-effective because of their simple design. The disadvantage of DC motors without motor control system is that they do not switch off automatically at increased torque, but draw more and more current until they come to a standstill. If a blockage is permanently present, the motor could become thermally defective.

Brushless DC motors, also called EC/BLDC motors, are motors that do not have carbon brushes. EC/BLDC motors operate in principle like three-phase synchronous motors. This is achieved by an electrical circuit that controls the coils one after the other.
The advantage of brushless DC motors is that they have a much longer service life due to the lack of carbon brushes and are maintenance-free. In general, EC motors are to be used for dynamic and higher speeds. The disadvantage of the motors are higher costs compared to stepper and DC motors.

Typical applications are model air planes, hard disc drives and PC fans. In the trade, EC/BLDC motors are gradually replacing DC motors in cordless screwdrivers and hand-held circular saws. And in the industry or in the field of automation technology, brushless DC motors are used for actuators, pick and place applications and in joints of industrial robots.

Conclusion

In summary, each motor has its advantages and disadvantages. But there is the right motor for every application!
igus® has a large product portfolio that consists of different sizes and different mounting parts for each motor. Mounting parts include e.g. encoders, brakes, clutches and gears.
In addition, igus® offers a wide variety of motor control systems for the respective motors in different price classes.

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