A motor system includes an air core motor having a rotor with opposed
permanent magnet poles defining therebetween a magnetic airgap and
driving magnetic flux across the magnetic airgap. A stationary armature
with air core windings is located within the magnetic airgap. The
permanent magnet poles produce a magnetic flux density through the air
core windings to produce a back emf in the windings comparable to the
voltage of the line power when the rotation of the permanent magnet poles
is synchronous with the line power. A electronic variable speed drive
coupled by a switch to the air core windings ramps up the frequency of
power to the air core windings for accelerating the rotor to near line
synchronous speed. When the frequency of the back emf approaches the
frequency of the line power, the switch decouples the electronic variable
speed drive and couples the air core windings to the line power for
synchronous operation.