The solution for the contact-free rotation is the magnetic bearings technology. The rotating shaft is held in by the electromagnetic forces generated in radial and axial directions.
The radial bearing rotor is equipped with ferromagnetic laminations which are held in position by magnetics fields created by the electromagnets placed on the stator.
The axial bearing is based on the same priciple. The rotor consits of a disk mounted perpendicular to the rotation axis, and opposite the electromagnets.
The rotor is levitated in the center without touching the stator. The rotor’s position is monitored by variable inductive sensors. These sensors detect any deviation from nominal position, and emit signals which command currents in the electromagnets in order to bring the rotor back to its nominal position.
MAGNETICS BEARINGS CONTROLLER AND UPS
The external controler drives the magnetic bearing located inside the machine. The controler is characterized by the rating of its power amplifiers supplying 300VDC at 30A. The controler is associated to a sophisticate UPS with internal batteries designed by Alpha Technologies. The UPS delivers 300V DC and 24V DC with a back up time of 5 minutes, the UPS is driven by its own controler in communication with the bearing controler.
The reliability of the UPS is essential: indeed the rotor speed is very high and in case of an interruption of the main, a procedure of rotor stop has to be launched to slow down the rotor speed before a stop. An immediate stop at full speed could destroy of the bearing.