The circuits were modified to allow the power to be
controlled using an external phase controller, which could
automatically and continuously adjust the microwave power
output from 0 to 1,000 W. Dimensions of the microwave
cavity were 44.5×42.0×38.9 cm. The fluidized bed consisted
of a cylindrical chamber with an inner diameter of 9 cm
(10 cm outside diameter), a height of 60 cm, and 12 kW
hot-air heaters controlled by a PID controller (with accuracy
of ±1 °C). The backward curve centrifugal fan was driven by a
1.5 kW motor connected to a frequency inverter to adjust the
air flow rate precisely.