Multiposition Valve Actuator

Triggering starts when the signal at port A exceeds 50% of the Nominal signal value. After the time set by the Switching-on time parameter has elapsed, the drive starts to move to the Push-pin stroke value. When the input signal at port A falls below 50% of the Nominal signal value, the drive reverses direction after the time specified by Switching-off time. Movement can be interrupted at an intermediate position. The graph shows the position of the actuator as a function of time.

In this graph, is the value of the Switching-on time parameter, which is divided into three time periods: , and . In the region, the drive is travelling at a constant acceleration and the positions are changing quadratically. In the area, the actuator moves linearly, at constant speed, in the direction of full extension of the spool. The actuator switches direction when the control signal is below 50% of the Nominal signal value:

If the Actuator positions parameter is set to 2, the Actuator travel direction parameter sets the direction of the spool movement.

The actuator movement can be interrupted at any time. If the pin movement is interrupted in the middle of the stroke, the ON/OFF time is set in proportion to the position of the spool relative to its stroke.

When Actuator positions is set to 3, the signal at port A sets the movement in the positive direction and the signal at port B sets the movement in the negative direction. Only one signal from one port is processed at a time. To switch control between ports A and B, i.e. between positive and negative motion control, the drive must first move to the neutral position. If the movement is interrupted in the middle of the stroke, the switch-on and switch-off times are set in proportion to the position of the spool valve relative to its stroke. The movement of the actuator can be interrupted at any time.

With signal control via A, a three-step actuator has the same travel characteristic as a two-step actuator with Actuator travel direction set to `Positive'. When the signal is controlled via port B, it has the same travel characteristic as a two-step actuator when Actuator travel direction is set to `Negative'.