Yet a-c drives also have inherent disadvantages in constant-torque applications such as extrusion, say detractors.
Others caution against potential thermal problems with a-c drives, particularly if a-c motors have not been tested for variable-frequency duty.
One application that has proven to be successful for a-c drives is on air rings and internal bubble cooling (IBC) systems of some blown film lines.
Another area in which a-c drives may have potential is in extrusion control.
Traditionally, a-c electronics have been more complex than those of d-c drives, making a-c drive systems more expensive.
C-TAC's Green cites an in-house cost survey, conducted last year, that compared average distributor pricing of a-c and d-c systems, including controllers, blowers, and motors, from 11 different drive manufacturers.
- the only major supplier of these drives in higher horsepower ranges - to combine the best characteristics of a-c drives and brush-type d-c drives.