The key to understanding how three-phase electric motors work is to have an accurate mental picture of the…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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Regulating the electric power sent to an electric motor is a task performed by high-speed switching…
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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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The simplest form of 4-20 mA current loop is the type used to represent the output of a process controller,…
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A limit switch detects the physical motion of an object by direct contact with that object. An example of a…
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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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Phasors are to AC circuit quantities as polarity is to DC circuit quantities: a way to express the…
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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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In order for any PID controller to be practical, it must be able to do more than just implement the PID…
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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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To better understand the design and operation of self-balancing pneumatic mechanisms, it is helpful to examine…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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A special type flowmeter suited for powdered or granular solids is the weighfeeder. One of the most common…
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Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…
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“Radio” systems use electromagnetic fields to communicate information over long distances through…
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Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…
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Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…
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Layer 1 of the OSI Reference Model is where we define the “physical” elements of a digital data…
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A variety of technologies exist to measure the quantity of stored material in a vessel. For liquid…
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Level gauges are perhaps the simplest indicating instrument for liquid level in a vessel. They are often found…
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As previously defined, calibration refers to the checking and adjustment of an instrument so that its output…
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Capacitors store energy in electric fields, proportional to the square of voltage. Inductors store energy in…
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At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication…
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Although it seems each model of PLC has its own idiosyncratic standard for programming, there does exist an…
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Calculus has a reputation for being difficult to learn, and with good reason. The traditional approach to…
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AC induction motors are based on the principle of a rotating magnetic field produced by a set of stationary…
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At the root of successful system diagnosis is a rigorous adherence to scientific reasoning. There exists no…
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As a general rule, high achievement only takes place in an atmosphere of high expectations. Sometimes these…
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Mechanical pressure-sensing elements include the bellows, the diaphragm, and the bourdon tube. Each of these…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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Electrical power grids primarily consist of three-phase AC circuits. This means most power lines (transmission…
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