Product Overview

Positioning the

Actuator with the

Controller

If the sensed media is within the controller’s setpoint range, the actuator can be positioned

by adjusting the controller setpoint up and down. Check for proper operation of the actuator

(valve or damper) while the actuator is being stroked.

Theory of Operation

Actuator variations are shown in Figure-24 through Figure-32. Refer to the actuator

selection tables beginning on page 3 to determine which Internal Wiring Figure applies to a

certain actuator.

The actuators are powered by shaded pole motors that are of the induction type, using what

is commonly know as a squirrel cage rotor. These motors, like all single phase induction

motors, must be provided with some means of starting. This is accomplished by the shading

coils in the poles of the motor and hence the name “Shaded Pole.” However, unlike most

single phase induction motors, the shading coils are also essential for running.

The field coil produces a magnetic field in the iron core (stator) and in the rotor. When

actuator terminal x is shorted to a terminal attached to CW shading coils, it causes a lag in

part of the field which provides the equivalent of a rotating field. This rotating field induces a

voltage and current in the rotor bars, and the attraction between the rotating field and these

current carrying bars pulls the rotor around with the field in a CW direction. When actuator

terminal x is shorted to a terminal attached to CCW shading coils, it operates the same

except it drives the actuator CCW. A voltage of 24 to 30 Vac with current of 9 amps is induced

in the shading coils in much the same manner as the secondary of a transformer.