Permanent magnet machines in magnetic bearings
In rotating machinery there exist mechanical and electrical losses. With the advent of more
efficient power-electronic devices, the shift has been towards reducing mechanical losses.
There are solutions that exist, such as air bearings and oil-mist bearings that go some way
to reducing these losses. In order to produce an even more efficient machine, windage
losses must be reduced. This can be achieved by placing the machine in a vacuum. It
becomes clear, therefore, that the bearing system can only be of the magnetic type.
An area of research interest that has developed as a result of higher-efficiency machines is
that of flywheel-energy storage systems. The most effective machine for flywheel energy
storage is the permanent-magnet machine. This does not require external excitation for
motoring or generating and is easier to operate as a generator than an induction machine.
In this work a permanent-magnet synchronous machine is designed and constructed, with
the aid of finite-element analysis. The rotor is a novel design which uses six magnets in a
two-pole configuration. This gives a rotor which is mechanically and magnetically good,
yet it does not require the use of a can. The testing of this machine shows a good
correlation between predicted and measured results.
When a permanent-magnerto tor is placed in bearingst hat allow it to move radially, there
exists an unbalanced magnetic pull between rotor and stator. These forces are predicted
using a finite-element method and then measured. These results are then used as a basis
for the design of an active magneticb earing The magneticb earingw as found to be able to
cope with these forces. The magnetic bearing itself was used as a novel way of measuring
the unbalanced magnetic forces, which required no contact between the rotor and the