SX25 Series Process Controller - Spirax Sarco
SX25 Series Process Controller - Spirax Sarco
SX25 Series Process Controller - Spirax Sarco
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3.4 Wiring examples 3.5 Auxiliary Relays for Valve Motor<br />
Drive actuators<br />
Example 1. <strong>SX25</strong>-mA for Pressure control: Using a 4-20mA<br />
pressure transmitter and a control valve with 4-20mA<br />
Electric or Electro-pneumatic positioner.<br />
<strong>SX25</strong>mA<br />
<strong>SX25</strong> VMD<br />
<strong>SX25</strong>mA<br />
When using <strong>SX25</strong> controller’s to directly drive VMD<br />
electric actuator’s, damage to the controller’s internal<br />
relays might occur due to switching the relatively<br />
heavy electrical loads.<br />
Auxiliary relays should therefore always be installed<br />
between the controller and the valve drive actuator.<br />
This will protect the controller from switching the<br />
actuators high current loads, avoid introducing high<br />
current loops within the proximity of the controller, and<br />
provide an easily replaceable switching element<br />
outside of the controller.<br />
Example2. <strong>SX25</strong>-VMD for Temperature control:<br />
Using Pt100 temperature sensor and a control<br />
valve with a Valve Motor Drive Elctric Actuator.<br />
18<br />
This advice is in line with that given by other<br />
manufacturers of similar equipment and is considered<br />
to be good working practice.<br />
IM-P323-25 CH Issue 3
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