Active Permanent Magnet (PM) Bias Homopolar Bearings
FMC Technologies’ Direct Drive Systems® business provides the only Active Permanent Magnet (PM) Bias Homopolar Bearings available today for high power machines.
The unique nature of Direct Drive Systems’ PM bearings provides a number of inherent user benefits:
- The bias flux is provided by the permanent magnets therefore eliminating the need for electrical current (and its associated losses)
- Greater efficiency versus conventional bearings
- Do not require any active cooling in the actuators for high loads
- The permanent magnet helper pole creates additional thrust load capability without the need of additional coils, current and controls
- The combination bearing includes a single bearing for both radial and axial positioning, occupies less space on the shaft and allows for higher speed operations and a more stiff and robust shaft
- Controller is extremely compact in size [L 15 in. (381 mm.), W 18 in. (457 mm.), H 9 in. (229 mm.), weight 42 lbs. (19 kg.)] compared to other controllers available today
Magnetic Bearing Technology
Magnetic bearings have been utilized by a variety of industries for over a decade with benefits that include non-contact rotor support, no lubrication and no friction.
Conventional mechanical bearings, the kind that physically interface with the shaft and require some form of lubrication, can be replaced by a technology that suspends a rotor in a magnetic field, which eliminates friction losses.
There are two types of magnetic bearing technologies in use today - passive and active. Passive bearings are similar to mechanical bearings in that no active control is necessary for operation. In active systems, non-contact position sensors continually monitor shaft position and feed this information to a control system. This in turn, based on the response commanded by the system, flows to the actuator via current amplifiers. These currents are converted to magnetic forces by the actuator and act on the rotor to adjust position and provide damping.
Additional benefits of magnetic bearings include:
- No friction
- No lubrication
- No oil contamination
- Low energy consumption
- Capacity to operate within a wide temperature range
- No need for pumps, seals, filters, piping, coolers or tanks
- Environmentally friendly workplace
- Impressive cost savings