User Guide

6. Reconnect the actuator wires to the controller.

7. Remove power from the actuator.

THEORY OF OPERATION

Refer to Figure-17 . The permanently sealed, oil-filled case contains a movable hydraulic

piston assembly and an electric pump/motor for the hydraulic system. The electric

pump/motor is powered by the input supply voltage and runs continuously, generating a fluid

pressure which is transmitted to the top of the piston. This fluid pressure creates a hydraulic

force which drives the piston downward. Opposing the hydraulic force is the spring of the

valve or damper linkage. When the hydraulic force becomes great enough to overcome the

opposing spring force, the piston translates downward, extending the output shaft.

The pump/motor contains a transformer winding which provides power to the Vdc power

supply. The power supply, in turn, provides power to the transducer assembly. To

proportionally position the shaft, first the control signal (135 Ω slidewire or the 4 to 20 mA)

input is compared to the shaft position feedback signal, through the actuator controller

circuit. Then, the actuator controller circuit emits an output signal which positions the flapper

in the transducer. The flapper opens or closes further to decrease or increase the hydraulic

pressure above the piston, resulting in an upward or downward movement at the shaft.

Figure-17 MPR-56XX and MPR-57XX Series Actuators.

REPLACEMENT PARTS

The installation of replacement actuators, in place of the obsolete series of MPR-56XX and

MPR-57XX actuators (refer to Figure-18 ), may require additional items. These replacement

items are required for the following reasons:

1. The AM-601 damper linkage is used to convert base actuators to damper actuators when

damper models are not available.

2. The AM-602 spacer is used when current actuators are installed on old linkages (refer

to Figure-19 and Figure-20 ).

3. The AE-249 transformer (208 Vac to 120 Vac) is used when replacing 208 Vac

actuators (MPR-5XX2) with 120 Vac actuators (MPR-5XX0).

Oil-Filled Case

Transducer

Assembly

Electric

Motor/Pump

Controller Printed

Circuit Board

Red

Blue

Yellow/White

Feedback

Vdc Power

Supply

Hydraulic Piston

Assembly

To AC Power

Source

Controller

Input