Electrical Drives
AC Controllers
Eddy-current Drives:
The primary elements of an eddy-current drive are an ac motor, an eddy-current clutch,
a tachometer, and a solid-state regulator. The eddy-current clutch consists of a drum
driven at constant speed by the ac motor and, concentric with the drum, a rotor
for driving a load.
Torque is transmitted from the drum to the rotor through an adjustable magnetic
field that is established in an air gap between the two members. The magnetic field
is produced by a coil on the rotor. Power for the coil, which is equivalent to about
2% of the drive rating, is provided by the regulator. The regulator adjusts coil
excitation to a level where output speed as indicated by a tachometer is equal to
that set on a speed-reference potentiometer.
Eddy-current drives typically have a 30-to-1 speed range at constant torque,
produce intermittent torque up to 200% of rated, provide 0.5% speed regulation from no
load to full load, and when stalled, deliver up to full-load torque without pulsations.
|
