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 key to understanding how three-phase electric motors work is to have an accurate mental picture of the…
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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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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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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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Modern DC and AC motor drives provide features useful when using electric motors as final control elements.…
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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 simple control system drawn in block diagram form looks like this: Information from the measuring device…
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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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Process measurements are often of an analog nature: the temperature of a furnace, the rate of fluid flow…
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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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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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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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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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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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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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Virtually any mass above absolute zero temperature emits electromagnetic radiation (photons, or light) as a…
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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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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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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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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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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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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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 vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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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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There are several different methods useful for causing an AC induction motor to brake, or slow down: DC…
Textbook
An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
Textbook
Three-phase AC is the dominant mode of electric power generation and distribution in modern societies.…
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Perhaps the simplest form of solid or liquid level measurement is with a float: a device that rides on the…
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A form of protection against faults on long-distance power lines is called distance relaying, so named because…
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A machine in the broad sense of the word is any device designed to translate some form of energy into useful…
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Converting between disparate units of measurement is the bane of many science students. The problem is worse…
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Earlier in this chapter you were shown a model of a nitrogen atom with a dense nucleus (comprised of protons…
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Learning from reading printed text is a kind of problem-solving activity it is own right. The problem is how…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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This section shows some of the many instrument symbols found in different types of technical diagrams used to…
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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 completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…
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The following animation shows the calculus concepts of differentiation and integration (with respect to time)…
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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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Another category of control strategies involves the use of signal relays or function blocks with the ability…
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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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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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A temperature switch is one detecting the temperature of some substance. Temperature switches often use…
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A 4 to 20 mA current signal represents some signal along a 0 to 100 percent scale. Usually, this scale is…
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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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