Brushless Motors

Brushless DC-motors from FAULHABER stand for maximum performance in the smallest space. They feature the highest values for speed, torque, and service life. They are very low in noise and vibration. They can even handle overload and continuous operation. The models range from the smallest micromotors to highly efficient flat servo motors and ultra-powerful motors with external rotor technology.

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What makes this motor type unique is in the name: it works without brushes. This means it does not require any sliding contacts, which ensure the transmission of current in conventional DC-motors (commutation). Instead, brushless DC motors use electronic commutation.

This is made possible by the inverse design of the brushless motor. The coil wound from copper wires acts as the stator, while the magnets act as the rotor. The control electronics direct the flow of current so that the coil produces a magnetic field that travels in a circle. This circular motion causes the magnetic rotor to rotate.

The windings of a brushless motor are divided into several parts, which are alternately energized. They each generate a magnetic field. A precisely controlled, constant change in the power supply to the individual parts of the winding creates a corresponding pattern in the change of the magnetic fields.

The attraction and repelling of the magnets "moves" circularly and sets the rotor in motion. With the vast majority of brushless motors, electronic sensors, so-called Hall sensors, constantly measure the position angle of the rotor. The motor electronics use their signals to switch the current on or off at the right time during the rotation or to reverse the direction of the current.

FAULHABER offers brushless motors with four different design principles. The two- and four-pole BLDC motors have an elongated cylindrical shape. Similar to the DC-motors, the winding is on the outside and the magnets on the inside, except that they perform the "reverse" function in the brushless variant: winding = stator, magnets = rotor.

In the two-pole motor, the rotor consists of a single magnet with a north and a south pole. In the four-pole motor, the rotor has two alternating north and south poles.

In a third version, the brushless motors of the B-Flat series feature a flat multi-pole design. In this model, three self-supporting windings are mounted on a circular stator disc. The rotor consists of a magnetic disc that is also circular. This unique layout enables an extremely flat design.

With the external rotor motors of the BXT series, the rotor magnets are on the outside and the windings – in this case with an iron core – are on the inside. The motors have 7 pairs of poles and, thanks to innovative winding technology, achieve an extremely high torque of up to 134 mNm. The ratio of torque to weight and volume is unrivalled.

FAULHABER offers a wide range of motor variants. There is almost always a drive available that offers the optimal solution for your application. We are also offering an equally wide range of gearheards, for example to extend the speed range or adjust the torque.

In the first step you have to define the basic parameters:

• Rated current and rated voltage
• Speed and torque
• Size (max. length and diameter)

Further criteria depend on the requirements of the mechanical integration. Important to consider here are, for example, the location and type of mounting points or the shaft diameter. The equipment of the drives must also match the external conditions of use. Adverse environmental influences such as extreme temperatures, negative pressure, humidity or dust can require a certain degree of protection, vacuum compatibility, or a corresponding temperature range. In many applications, the noise and vibration level of the drives is also important.

Since brushless motors do not require sliding contacts, there is no abrasion due to the commutation. Unavoidable wear only occurs on the bearings, but they have a much longer service life than brushes. Depending on the operating conditions, BLDC motors can therefore have a service life of more than 25,000 hours, which is around five times that of brushed DC-motors. Without brushes, the motors also have very low noise emissions. The same goes for the speed: brushless motors can reach up to 100,000 rpm, around four times that of brushed DC-motors.

Brushless DC-motors require significantly more complex electronics than brushed DC-motors. Accordingly, they are more expensive and require more effort when it comes to integrating them. Because the coil is fixed and the magnets move, the moment of inertia is greater with brushless motors. They require a higher starting voltage, but at the same time they can withstand more overload. They are also available as flat servo motors with a very short overall length.

Brushed DC-motors, on the other hand, are comparatively easy to control and integrate. They do not require a feedback loop and, in theory, only require a DC voltage connection. This simple design allows particularly cost-effective solutions. In the DC-motors from FAULHABER, a self-supporting ironless copper winding with a very low mass and correspondingly minimal moment of inertia rotates. They deliver high performance even at a very low starting voltage and can also work at low speeds. This is especially important when they are operated by battery power. At the same time, these DC-motors can change their speed very quickly. However, due to the low moment of inertia, their overload capacity is limited.