Calnetix Technologies specializes in high-speed rotating machinery supported by patented active magnetic bearings (AMBs), which help optimize system efficiency and enhance reliability and sustainability.
We have developed numerous magnetic bearing systems used in a wide variety of commercial systems, including high-efficiency blowers, high-speed compressors, Organic Rankine Cycle (ORC) systems and many more. We have been able to reduce the costs associated with magnetic bearing integration by improving the manufacturing processes of our magnetic bearing components and further optimizing our controllers, which are a substantial percentage of the overall system cost.
We offer Powerflux™ Magnetic Bearings in radial and side by side combination configuration and Xcelflux™ Magnetic Bearings with a unique coil architecture. The unique advantages of Calnetix’s active magnetic bearings include the following:
Powerflux™ AMBs utilize homopolar permanent-magnet-bias magnetic fields in conjunction with an electromagnetic field, whereas Xcellflux™ AMBs use heteropolar electromagnetic bias fields in conjunction with electromagnetic control fields. Both products are low-cost and easy to assemble, as shown and described below.
Magnetic bearings do not function on their own; they require multiple components working together as a unique system. Calnetix has designed and developed all of the components that make up the active magnetic bearing system, and these components are shown and described below.
The actuator in an Active Magnetic Bearing (AMB) is the electromagnet that applies a controlled force to the shaft of a machine to control its position. A radial actuator consists of a lamination stack with control coils and poles arranged to give two orthogonal axes of control. An arrangement of permanent magnets is also used in Calnetix actuators to produce a linearizing bias flux. Other AMB manufacturers produce the linearizing flux with a DC current in the control coil. Two other common actuator configurations are a combination radial/axial actuator and a stand-alone axial actuator.
An AMB actuator must be connected to a Magnetic Bearing Controller (MBC) that supplies the control current to the coils based on a position sensor feedback signal and a control algorithm.
A position sensor is a device capable of sensing shaft displacement (position) with a wide bandwidth. In Active Magnetic Bearings (AMB), information from the position sensors is used by the Magnetic Bearing Controller (MBC) to control the actuator coil currents, and thus the magnetic force on the shaft. Most often the position sensor will include a sensor head (transducer) in the machine adjacent to the magnetic actuator and drive/demodulation electronics in the MBC.
A speed sensor is a device capable of measuring rotational speed of the shaft about its spin axis. Information about the shaft speed is used by the MBC to ignore the synchronous component of the shaft position variations, thus allowing the shaft to spin about its center of mass. This feature minimizes transmission of the shaft vibrations due to unbalance to the housing of the machine and reduces the load on the magnetic bearings.
Backup bearings provide support for the rotating assembly when the magnetic bearing system is deactivated, and provide rotor support in the event of an overload of the magnetic bearings or a failure of some component of the magnetic bearings. In normal operation, the backup bearings are not active as they will have a small radial and axial clearance to the rotating assembly. This clearance is at most one-half of the magnetic bearing air gap and typically considerably smaller.
The most common backup bearing configuration used by Calnetix is two duplex pairs of angular contact ball bearings preloaded face-to-face (DF). This mounting requires the bearing outer races to be clamped – either hard or through a spring – on the outer race. Hybrid bearings with conventional SAE 52100 steel races and SiN3 balls are standard. Backup bearings for high-speed applications are usually cageless and use either a grease film, dry film lubricant or a light grease fill.
Calnetix Technologies has developed and deployed advanced Magnetic Bearing Controllers (MBCs) that contain all of the elements necessary to operate magnetic bearing systems. The company currently produces two different MBC platforms in the Insight™ series and one in Concurrence™ series.
For more information, see the Magnetic Bearing Controllers product page.
The Calnetix Service Graphical User Interface (GUI) is used for system setup, monitoring, diagnostics and system identification. The upper half of the front panel, shown below, displays orbit plots from the two radial bearing sensors and a time history plot from the axial bearing sensor. Other operating variables shown include spin speed, static current, and synchronous displacement and current. Status variables, such as levitation and fault status, are indicated as well. A system Information window on the right gives version information for the GUI, firmware, parameter file and machine serial number specifier.
More detailed information or functionality can be accessed through the action buttons: Digital Signal Processors (DSP) Actions, View Logs, Fault Summary, View/Set Parameters and Measurements. The additional functionality includes:
Active Magnetic Bearings (AMBs) have been in commercial rotating machinery for over 30 years, offering increased performance and extended machine lifespan due to frictionless operation and the lack of wearable parts. There has been an industry-wide increase in the production of magnetic bearing systems, which has led to overall cost reduction and more rapid market adoption. Some of the advantages of switching to magnetic bearings, include:
To see more information about AMB advantages, click here.
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How A Magnetic Bearing Controller Works
Advantages of Magnetic Bearings
Transient Simulation of Magnetic Bearing and Backup Bearing Interaction in a High Speed Rotary Atomizer Subjected to Impulsive Loads
Demonstrated Operability and Reliability Improvements for a Prototype High-Speed Rotary-Disc Atomizer Supported on Active Magnetic Bearings