Smooth running and outstanding efficiency
Small electric motors are used for a variety of drive tasks. In addition to mechanical quality, smooth running plays an important role. Rotek has therefore developed a particularly quiet-running synchronous motor.
There are applications in which drives should operate as quietly and with as little vibration as possible. The high and low frequencies should not be too dominant and individual sounds should not be too prominent. The aim is to achieve the softest, smoothest, barely audible whirring possible. Drives that are used in living rooms should not cause any disturbing background noise. But they should also be as quiet as possible in laboratories and hospitals.
Rotek has been manufacturing synchronous motors in Bremerhaven for many years and offers a modular system with which millions of product variants are possible. Synchronous technology is advantageous for many applications. Thanks to powerful magnetic rotors and efficient coil body winding, synchronous motors are particularly energy-saving and extremely compact compared to conventional capacitor and three-phase motors. They deliver constant speeds regardless of the load and allow starts and stops within fractions of a second. Another typical feature is the self-holding torque, which makes a brake superfluous.
However, the self-holding torque is a disadvantage when it comes to noise generation. This is because the magnetic “engaging” of the rotor poles in the stator teeth generates vibrations that are noticeable as structure-borne noise. Whether the human ear perceives something as loud is determined, among other things, by the frequency and timing of the sound. Some frequencies are perceived as louder than they actually are. We find piercing, shrill sounds such as whistling and squeaking unpleasant. We find sound events with inharmonic frequencies disturbing. Low, harsh sounds such as buzzing and humming are also perceived negatively.
“The application of a customer in Scandinavia was the trigger for us to think about how we could reduce these unwanted vibrations,” explains Rolf Treusch, responsible for the commercial area at Rotek. “In this case, our motors were used in access systems. The structure-borne noise generated by the motor's rotation caused the housing to vibrate, resulting in unpleasant noises.”
Minimize vibrations
So Rotek set about developing a motor that generated fewer vibrations and therefore ran more quietly. The result was the extremely smooth-running Roslyde motor, whose design was christened “SmoothDrive Technology”.
How was this goal achieved? Klaus Treusch, the technical manager and developer, explains it like this: “The first starting point for minimizing noise should always be the motor itself as the source of vibrations.” During the development of the Roslyde, Rotek made two main adjustments in order to achieve the quietest and lowest-vibration running behavior possible.
The alternating magnetic field circulating in the stator winding causes the drive to oscillate. This effect was minimized through targeted optimization of the winding technology. At the same time, the usual cogging torque for synchronous motors was reduced to a minimum through design adjustments to the magnetic rotor. High precision in production is crucial for this.
The rotor is ground so precisely between two points that no further balancing is required. Unwanted noise can also be caused by the bearings. The more precise they are, the better. As Rotek always uses high-quality ball bearings with special lubrication, no changes were necessary in the motor bearing area either. And attention is paid to symmetrical bearings in the particularly precise machining of the end shields.
View the entire drive unit
However, there are a number of other factors that can play a role: The noise level of a drive depends crucially on the mechanical components such as the gearboxes. “You should always consider the entire drive unit, as the majority of all small motors are combined with gearboxes,” Klaus Treusch continues. The motor vibrations are transmitted to the gearbox. At the same time, the mechanical gearbox components generate running noises.
Therefore, in addition to precision, the type of gearing and backlash play a particularly important role in noise development. Lubricants and damping gear materials such as hard fabric and modern plastics also have a major influence. It is not just the audible airborne noise that is important in the drive. Vibrations can cause the housing of the entire application to oscillate, acting like a resonating body. In addition to unpleasant vibrations, the amplified structure-borne sound of the drive also generates unwanted noise emissions. For noise-sensitive applications, Rotek therefore offers low-noise gearboxes which, together with the low-vibration Roslyde, form a particularly quiet drive unit.
Many advantages
Roslyde motors are preferably used to drive the screw conveyors in pellet stoves and kitchen stoves. They are located in living rooms and disturbing background noise is undesirable. This also applies to laboratories. There, Roslyde motors in dosing pumps and analysis devices do their work quietly.
HahnenuferRotary heat exchangers in ventilation systems use Roslyde motors to turn the rotor. They are increasingly being used in building ventilation technology to transfer the heat from the warm exhaust air to the incoming cold supply air. This was implemented, for example, in the residential project „Den Grønne Karré“ in Copenhagen.
Electric actuators are another field of application for Roslyde motors. The decisive factor for the customer here was that normal synchronous motors generated too much vibration. The low-vibration Roslyde was therefore chosen.
Due to their design and good efficiency, Roslyde motors are also ideal for temperature-critical applications. Most models only have a very low self-heating of 20-50 K (degrees Kelvin).
In areas with high ambient temperatures, these do not increase as much if the motor itself emits less heat during operation. When producing ice or in the vicinity of chilled food, a motor with low self-heating ensures that less cooling is required. This also saves energy.
Roslyde motors can be found in pipelines, for air conditioning large rooms and in the water supply in swimming pools, to name but a few.
Particularly efficient as a three-phase version
The Roslyde motors with SmoothDrive Technology are not only characterized by quiet, smooth running and low-vibration behaviour. Another plus point: they are very energy-efficient. As three-phase motors in particular, they achieve outstanding efficiencies of up to 90 percent with low self-heating. The single-phase motors offer power outputs of 11 to 20 W, while the three-phase versions achieve up to 40 W. As four-pole motors, they have a speed of 1500 rpm at 50 Hz. In addition, the three-phase Roslyde motors can be operated very well on frequency inverters in the range from 1 to 70 Hz.
Special windings up to 3~500 V are possible on customer request. “Finally, during development, we took great care to ensure that the Roslyde motors fit perfectly into our modular system,” reports Rolf Treusch. “This means that practically no new parts are required and they can be combined with all existing motors and gearboxes.” Other options include special gearboxes, mechanical adaptations to the housing and special shafts, individual power connections with special cables and plugs and, finally, optional accessories such as encoders.
Advantages
- low vibration
- little self-heating
- good efficiency
- low-noise
- smooth running
Areas of application
- rotary heat exchanger
- pellet stoves and pellet kitchen stoves
- actuators
- access systems
- dosing pumps and analyzers
Low-noise motors Roslyde
contact
27580 Bremerhaven
GERMANY
rotek-motoren.de