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Actuators

Course: Process Control, NMBU. Dec 2017 - April 2018. Actuators. By Finn Aakre Haugen, PhD, TechTeach (finnhaugen@hotmail.com). Valves Pumps Motors Heaters. Where is the actuator in the control loop?. Control valve. Here is a pneumatic

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Actuators

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  1. Course: Process Control, NMBU Dec 2017 - April 2018 Actuators By Finn Aakre Haugen, PhD, TechTeach (finnhaugen@hotmail.com) F. Haugen. Process Control. NMBU. 2017.

  2. Valves • Pumps • Motors • Heaters Where is the actuator in the control loop? F. Haugen. Process Control. NMBU. 2017.

  3. Control valve Here is a pneumatic control valve, using air pressure to manipulate the valve opening. Valves are used to manipulate gas and liquid flows. F. Haugen. Process Control. NMBU. 2017. [http://en.wikipedia.org/wiki/Control_valves]

  4. Control valve Principal design of a pneumatic control valve: Air pressure supply Control air pressure Control signal (from controller) IP-converter (from current (I) to pressure (P)) Spring Indicator displaying valve opening Packing box Plug Fluid outlet Seat Fluid inlet F. Haugen. Process Control. NMBU. 2017. [http://nn.wikipedia.org/wiki/Reguleringsventil + FH]

  5. Centrifugal pump: The most common pump type in industry. F. Haugen. Process Control. NMBU. 2017. [http://en.wikipedia.org/wiki/Pump]

  6. Peristaltic pump (displacement pump): Applied for small, precise liquid flows, in dosing applications. Rotational speed is manipulated with voltage or current. F. Haugen. Process Control. NMBU. 2017. [http://en.wikipedia.org/wiki/Pump]

  7. AC-motors are controlled (manipulated) by frequency converters. AC-motors(Fans; Pumps; Conveyors; Compressors.) F. Haugen. Process Control. NMBU. 2017. [http://en.wikipedia.org/wiki/Electric_heating]

  8. Example: Motor control The purpose of a frequency converter is to convert the "fixed" alternating mains voltage (e.g. 230 V, 50 Hz) to an alternating voltage with variable amplitude and frequency appropriate to control the rotational speed of an AC-motor. F. Haugen. Process Control. NMBU. 2017.

  9. Actuator: Heating element (resistor) It can be manipulated using PWM... (next slide) F. Haugen. Process Control. NMBU. 2017. [http://en.wikipedia.org/wiki/Electric_heating]

  10. Principle of pulse-width modulation (PWM) : Purpose of PWM: To deliver approximately continuous (analog) power to a process using relatively quick On/Off-switching of the power source. Typical applications are electrical heaters and motors. F. Haugen. Process Control. NMBU. 2017.

  11. Application of PWM for temperature control The SSR (Solid State Relay) switches the mains in/out over the heating element. In average the process receives power which is proportional to the control signal from the PID controller, hence analog power supply, even if the power is actually turned on/off! F. Haugen. Process Control. NMBU. 2017.

  12. Simulator of PWM-controlled actuator in aPID control system(download and unpack zip-file, then run exe-file) F. Haugen. Process Control. NMBU. 2017.

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