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.…
Textbook
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.…
Textbook
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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