Permanent Magnet (PMAC) Motors

The PMAC (Permanent Magnet AC) motor is traditionally of a more
complex construction than the standard induction motor. 

With the new motor type, the design has been simplified by using powerful permanent magnets to a constant flux in the air gap.

There by eliminating the need for the rotor windings and brushes normally used for excitation in synchronous motors. 

This results in the accurate performance of a synchronous motor, combined with the robust design of a
standard induction motor. 

The motor is energized directly on the stator by the variable speed drive.

Benefits of a PMAC Motor

Standard induction motors are not particularly well suited for low-speed
operation as their efficiency drops with the reduction in speed. 

They may also be unable to deliver sufficiently smooth torque across the
lower speed range. 

This is normally overcome by using a gearbox. 

The new solution provides a high torque drive coupled directly to the load.

By eliminating the gearbox, the user saves space and installation costs,
as he only needs to prepare the foundations for one piece of machinery.

This also gives more freedom in the layout design.

The PMAC motor can deliver more power from a smaller unit. 

For instance, powering the in-drives of a paper machine directly at 220 to 600 r/min with a conventional induction motor would require a motor
frame substantially larger than that of a 1500 r/min motor.

Using permanent magnet motors also means higher overall efficiency and less
maintenance.