For additional assistance, please contact Toshiba Adjustable Speed Drive Marketing Dept. at (800) 872-2192
Page: 1 of 6
Pressure
Transducer
Air Flow
Damper
Damper
Damper
Area in which constant
pressure is desired
4-20 mA Feedback
Q9
APPLICATION GUIDELINE 1.1
Process PID
Introduction
The built-in Process PID control of the Q9 can be used to maintain a constant process variable such
as flow, pressure, temperature, or level. In the example below, the Q9 is being used to vary the speed
of the motor/fan to maintain a constant static pressure in the ductwork. As the dampers on the output
side of the fan are opened, the static pressure in the system will begin to drop. The drive senses this
change in static pressure via a 4-20mA feedback signal and the drive will increase the speed of the
motor/fan to bring the static pressure to the desired level. Conversely, the drive will slow the
motor/fan down as the dampers close to compensate for the increase in pressure. The rate at which
the drive responds to changes in the feedback signal is adjustable via three parameters (Proportional
Gain, Integral Time, and Differential Time) and will need to be field-tuned.
