Split-Range Controllers

摘要

The most common split-range application is the heating and cooling of the barrel zones of plastics extruders (figure 1). On startup, the heat output of the controller takes the barrel zone up to working temperature. Heat delivery is usually modulated (that is, turned up or down) using the time-proportioning mode, by magnetic or solid-state contactors. A calrod-type heater element would be embedded in the heat/cool unit (two half - cylinders of cast aluminum that clamp on to part of the barrel). The cool output could be water or heat transfer fluid, piped through coils in the same cast aluminum unit. Alternatively the cast aluminum unit would be finned, and heat is removed by blown air. Cooling would be modulated by pulsing a solenoid valve or fan motor contactor in the same manner as the heat is pulsed.