Magnetic Lines of Force (MMF)

Lines of magnetic force (MMF) have an effect on adjacent conductors and even itself. This effect is most pronounced if the conductor overlaps itself as in the shape of a coil.

Figure. Magnetic Self-Inductance

Any current-carrying conductor that is coiled in this fashion forms an Inductor, named by the way it induces current flow in itself (selfinductance) or in other conductors.


Inductance (L, Henrys)

Opposition to current flowing through an inductor is inductance. This is a circuit property just as resistance is for a resistor. The inductance is in opposition to any change in the current flow. The unit of inductance is Henry (H) and the symbol is L.


Frequency (f, Hertz)

Any electrical system can be placed in one of two categories direct current (dc) or alternating current (dc). In dc systems the current only flows in one direction. The source of energy maintains a constant electromotive force, as typical with a battery. The majority of electrical systems are ac. Frequency is the rate of alternating the direction of current flow. The short form is f and units are cycles per second or Hertz (short-formed to Hz).


Reactance (X, Ohms)

The opposition to alternating current (ac) flow in capacitors and inductors is known as reactance. The symbol for capacitive reactance is XC and for inductive reactance XL.

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Magnetic Flux (Unit of Measurement is Webers)

When current flows in a conductor, a magnetic field is created around that conductor. This field is commonly presented as lines of magnetic force and magnetic flux refers to the term of measurement of the magnetic flow within the field. This is comparable to the term current and electron flow in an electric field. The following illustration shows the direction of magnetic flux around a conductor and the application of the easily remembered right-hand-rule. Mentally, place your right hand around the conductor with the thumb pointing in the direction of current flow and the fingers will curl in the direction of magnetic flux.

Although we will not go into the derivation of the values, it can be shown that when f is the frequency of the ac current:

XL= 2 (Phi) f L

XC=1/2(Phi)fC

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Level switches

A level switch is one detecting the level of liquid or solid (granules or powder) in a vessel. Level
switches often use floats as the level-sensing element, the motion of which actuates one or more
switch contacts.
Recall that the “normal” status of a switch is the condition of minimum stimulus. A level switch
will be in its “normal” status when it senses minimum level (e.g. an empty vessel).

Level switch symbols
Two water level switches appear in this photograph of a steam boiler. The switches sense water
level in the steam drum of the boiler. Both water level switches are manufactured by the Magnetrol
corporation:
The switch mechanism is a mercury tilt bulb, tilted by a magnet’s attraction to a steel rod lifted
into position by a float. The float directly senses liquid level, which positions the steel rod either
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238 CHAPTER 8. DISCRETE PROCESS MEASUREMENT
closer to or further away from the magnet. If the rod comes close enough to the magnet, the mercury
bottle will tilt and change the switch’s electrical status.
This level switch uses a metal tuning fork structure to detect the presence of a liquid or solid
(powder or granules) in a vessel:
An electronic circuit continuously excites the tuning fork, causing it to mechanically vibrate.
When the prongs of the fork contact anything with substantial mass, the resonant frequency of
the structure dramatically decreases. The circuit detects this change and indicates the presence
of material contacting the fork. The forks’ vibrating motion tends to shake off any accumulated
material, such that this style of level switch tends to be resistant to fouling.
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8.6. LEVEL SWITCHES 239
Yet another style of electronic level switch uses ultrasonic sound waves to detect the presence of
process material (either solid or liquid) at one point:
Sound waves pass back and forth within the gap of the probe, sent and received by piezoelectric
transducers. The presence of any substance other than gas within that gap affects the received audio
power, thus signaling to the electronic circuit within the bulkier portion of the device that process
level has reached the detection point. The lack of moving parts makes this probe quite reliable,
although it may become “fooled” by heavy fouling.

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Pressure switches

A pressure switch is one detecting the presence of fluid pressure. Pressure switches often use
diaphragms or bellows as the pressure-sensing element, the motion of which actuates one or more
switch contacts.
Recall that the “normal” status of a switch is the condition of minimum stimulus. A pressure
switch will be in its “normal” status when it senses minimum pressure (e.g. n applied pressure, or
in some cases a vacuum condition)1.

Pressure switch symbols

The following photograph shows two pressure switches sensing the same fluid pressure as an
electronic pressure transmitter (the device on the far left):

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Series and parallel circuits

Impedance in a series circuit is the orthogonal sum of resistance and reactance:
Z =(R2 + (X2L− X2C)) ^1/2
Equivalent series and parallel circuits are circuits that have the exact same total impedance
as one another, one with series-connected resistance and reactance, and the other with parallelconnected
resistance and reactance. The resistance and reactance values of equivalent series and
parallel circuits may be expressed in terms of those circuits’ total impedance:

If the total impedance of one circuit (either series or parallel) is known, the component values of
the equivalent circuit may be found by algebraically manipulating these equations and solving for
the desired R and X values:
Z2 = RseriesRparallel


Z2 = XseriesXparallel

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Electron versus conventional flow

When Benjamin Franklin advanced his single-fluid theory of electricity, he defined “positive” and
“negative” as the surplus and deficiency of electric charge, respectively. These labels were largely
arbitrary, as Mr. Franklin had no means of identifying the actual nature of electric charge carriers
with the primitive test equipment and laboratory techniques of his day. As luck would have it,
his hypothesis was precisely opposite of the truth for metallic conductors, where electrons are the
dominant charge carrier.
This means that in an electric circuit consisting of a battery and a light bulb, electrons slowly
move from the negative side of the battery, through the metal wires, through the light bulb, and on
to the positive side of the battery as such:

Unfortunately, scientists and engineers had grown accustomed to Franklin’s false hypothesis long
before the true nature of electric current in metallic conductors was discovered. Their preferred
notation was to show electric current flowing from the positive pole of a source, through the load,
returning to the negative pole of the source:

This relationship between voltage polarity marks and conventional flow current makes more
intuitive sense than electron flow notation, because it is reminiscent of fluid pressure and flow
direction:

If we take the “+” sign to represent more pressure and the “-” sign to represent less pressure,
it makes perfect sense that fluid should move from the high-pressure (discharge) port of the pump
through the hydraulic “circuit” and back to the low-pressure (suction) port of the pump. It also
makes perfect sense that the upstream side of the valve (a fluid restriction) will have a greater
pressure than the downstream side of the valve. In other words, conventional flow notation best
honors Mr. Franklin’s original intent of modeling current as though it were a fluid, even though he
was later proven to be mistaken in the case of metallic conductors where electrons are the dominant
charge carrier.

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FLUID MECHANICS | Gas Laws

The Ideal Gas Law relates pressure, volume, molecular quantity, and temperature of an ideal gas
together in one neat mathematical expression:
PV = nRT
Where,
P = Absolute pressure (atmospheres)
V = Volume (liters)
n = Gas quantity (moles)
R = Universal gas constant (0.0821 L · atm / mol · K)
T = Absolute temperature (K)
An alternative form of the Ideal Gas Law uses the number of actual gas molecules (N) instead
of the number of moles of molecules (n):
PV = NkT
Where,
P = Absolute pressure (atmospheres)
V = Volume (liters)
N = Gas quantity (moles)
k = Boltzmann’s constant (1.38 × 10−23 J / K)
T = Absolute temperature (K)
Although no gas in real life is ideal, the Ideal Gas Law is a close approximation for conditions of
modest gas density, and no phase changes (gas turning into liquid or visa-versa).
Since the molecular quantity of an enclosed gas is constant, and the universal gas constant must
be constant, the Ideal Gas Law may be written as a proportionality instead of an equation:
PV ∝ T
Several “gas laws” are derived from this Ideal Gas Law. They are as follows:
PV = Constant Boyle’s Law (assuming constant temperature T)
V ∝ T Charles’s Law (assuming constant pressure P)
P ∝ T Gay-Lussac’s Law (assuming constant volume V )
You will see these laws referenced in explanations where the specified quantity is constant (or
very nearly constant).

For non-ideal conditions, the “Real” Gas Law formula incorporates a corrected term for the
compressibility of the gas:
PV = ZnRT
Where,
P = Absolute pressure (atmospheres)
V = Volume (liters)
Z = Gas compressibility factor (unitless)
n = Gas quantity (moles)
R = Universal gas constant (0.0821 L · atm / mol · K)
T = Absolute temperature (K)
The compressibility factor for an ideal gas is unity (Z = 1), making the Ideal Gas Law a limiting
case of the Real Gas Law. Real gases have compressibility factors less than unity (< 1). What this
means is real gases tend to compress more than the Ideal Gas Law would predict (i.e. occupies less
volume for a given amount of pressure than predicted, and/or exerts less pressure for a given volume
than predicted).

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The Thermodynamic Laws

The laws of thermodynamics explain the effects of heat in an engine. The first law states that energy can be changed but it cannot be destroyed. In a gas turbine engine, heat energy is changed to mechanical energy. The second law of thermodynamics states that heat cannot be transferred from a cooler body to a hotter body. In a gas turbine engine, heat is transferred from the hotter engine to the cooler lube oil.

Newton's first law explains why a force is needed to make the gas turbine work. In the figure, a ball on a level table will not move until it is made to move by some force such as the wind or pushing it by hand. Similarly, until the fuel and air mixture is burned in the gas turbine, there is no force for the turbine to use to turn the rotor shaft.

Newton's Second Law explains why the air must be compressed and accelerated to create a force. In the figure, a hammer is used to drive a nail. The force of hitting the nail is proportional to the mass (weight) of the hammer multiplied by the velocity of the hammer when it hits the nail. If you also use a heavier hammer, it is even easier to drive the nail into the wood. Mass and acceleration directly affect the amount of force created. The more compressed air (mass) that enters the gas turbine, the more force created from the combustion process.

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Osmosis Power Generation

 The need for energy sources, especially electrical energy, encouraging the emergence of many variations of the source of power. Moreover the pressure to create environmentally friendly power source, be one motivating factor to find energy sources other than fossil fuels. One that is currently busy with the concept of renewable energy plants that are already developed in many countries - developed countries. One part of the renewable energy power plants use osmosis energy techniques will be discussed in this article.
In principle, the power generation process involves a change of kinetic energy into electrical energy (turning on the generator rotor). The kinetic energy is commonly the case. This is due to the generation of the conventional methods (such as fossil fuel) fuel will be burned to heat water, which in turn will generate the pressure to rotate the rotor. It is then seen and tried to be utilized in the process of osmosis.
Based on the understanding, Osmosis is one of the properties owned by the liquid (fluid) to move through the fluid layer between 2 semiperrmiabel that have different density. Semipermeable layer serves to separate the two layers and can only be penetrated by water, while other particles are retained. So that the direction of movement of fluid from the fluid with a low density to higher density of the fluid to achieve the same density.
This will result in the displacement of fluid volume changes that also result in pressure on the fluid side is more concentrated. This pressure would then cause the movement of fluid and pressure that can be used as a source of kinetic energy. The concept is then used in power plants with the concept of osmosis technique with the use of seawater. By utilizing the density of sea water and pure water, generating electricity by osmosis technique can be developed.
To better understand the process of osmosis, can be seen in the image below.

On the initial conditions

During the process of osmosis has reached the point of balance
Osmosis technique is used at power plants have two distinct types, namely the PLO SHEOPP Converter and Underground Plant.
SHEOPP Converter
SHEOP Converter is a power plant installed at the bottom of the sea surface. Principles used in these plants is to use sea water as the fluid is concentrated, and utilize the flow of a river or dam which serves as a less dense fluid. Laying the basis of this plant on account of the towing also content of different heights and density of sea water itself. This factor is affecting the electrical energy that can later be resurrected.

SHEOPP Conversion Plant

PLO Underground Plant
In principle, this type of power plant Undergorund PLO has the same working prinsio SHEOPP Converter. The difference lies in the placement of plants. If the SHEOPP Converter, generator placed on the seabed to make sure the pressure and amount of fluid is right, then at power generating plant type Undergorund PLO laid under the ground. It is based to bring the pressure differential, with water from rivers or dams and sea water to the lower pressure level. For more details, can be seen in the figure below:

PLO Underground Plant
However, like many other renewable energy generation, the concept of osmosis plant with a technique still got a lot of challenges. This corresponds to a factor - a factor of quality, quantity, and economically unfavorable. The problems mainly focused on the ability of semipermeable layer as an important part of this technique, and also the cost factor needed to produce electrical energy per Watt-nya.Oleh because it's still a little power plant that was developed with this technique.
Development of plants with this technique until now, there are only a few places, such as the company Starkraft in Tofte, Norway and Eddy Potash Mine in New Mexico. Even when it was first built, the power plant in Norway is only able to produce several kilo-Watt that if converted to heat water for only 1-2 kettle.
Attention on this plant was finally draw some parties to examine and explore further. One is concern for increased work on the side semipermiabelnya layer. However, as time went on, not something that is not possible if the future generation with this technique can be one part of the basic system of power plants with renewable energy.

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Power Systems

On Power Systems are the use of an electronic component which is generally used in a series of electric motors settings. Electronic components used in electrical power systems, in principle, be capable of producing large power or be able to withstand large power dissipation.

Includes switching power electronics, control and modifier (conversion) large blocks of electric power by means of semiconductor devices. Thus the power electronics broadly divided into 2 (two) parts:
A. Power circuit2. The control circuit
In the following figure shows the relationship between the two sets above are integrated into one, where they are making use of semiconductor devices.

Power circuit components consist of diodes, thyristors and power transistors. While the control circuit consisting of diodes, transistors and integrated circuits (Integrated Circuit / IC).
By using similar equipment reliability and compatibility of the equipment (system) will be repaired. Power electronics is an important part of industries, namely in the power control systems, processes and other electronics.
I. DIODE
Diode is a union of P and N layers as images and symbols layer structure.


Terms of diodes in the ON state is positive Vak Vak while OFF is negative.


These characteristics describe the relationship between current diode (IR and IF) to Vak in the current conditions hold (OFF) or in a state of flow (ON). In the OFF state, Vak = Vr = negative, the diode current holding but there is a small leakage current Ir.
In the ON state, Vak = Vf = positive, but there is a current of the diode voltage drop across the diode Vf = Δ, and if Δ Vf is the greater for the higher diode currents, meaning * If the conduction loss Δ Vf up. Seen also on the characteristics of the diode above that when Vr is too high diode will be damaged.
Switching characteristics
These characteristics describe the nature of the work shift diodes in the ON state to OFF and vice versa.


Diode current will soon pass if Vr has reached more than the minimum diode Vf conducive and OFF at a delay of having to re-diode reverse voltage blocking capability. From the picture above tgerlihat of instantaneous reverse flow in the diode, where the reverse flow occurs at the transition state of the diode from ON state to the reverse voltage blocking conditions.
Given the nature of the reverse flow, the obtained two types of classification of the diode is:A. Fast diodes, ie diodes with Traffic immediately capable of blockingrapid reverse voltage, the order of 200 ns starting from the diode forward currentequal to 0 (zero).
2. Slow diodes, ie for the same diode requires a longer time,Q32> Qs1.
Terminology diode characteristics
Trr Reverse Recovery Time, the time it takes to be blocking diode forward voltage.Tjr: The time required by a PN junction to be blocked.TBR: The time required to form a border zone blocking Junction.Qs: The amount of charge that flows in the reverse direction during the movement of the diode ON to OFF status.
Diode type is used on a much slower converters with commutation slow / natural, such as the rectifier circuit. While Fast Diode type static converter used in the commutation itself, such as the DC Chopper, the converter commutation own dll.
The voltage capability
Reverse voltage blocking diode is, was able to withstand voltage depends on the characteristics of the voltage itself.


VRWM = normal peak working voltage.VRRM = peak overvoltage that occurs periodically.VRSM = Peak voltage is not periodic.
Diode current capability
The existence of Δ conduction voltage drop Vf diode causes power loss at the exit in the form of heat. The maximum junction temperature lies between 110 ° C - 125 ° C. Heat in excess of this temperature will cause diode damage. This maximum temperature can be achieved by a variety of load currents of the diodes.


If (AV): The current average of the maximum allowable each average current price would result in a price of final temperature on the junction diode. If the limit (AV) is also dependent on ambient temperature and type of cooling system (heat-sink).
If (RMS): maximum diode current effective price. Average price is below If (ΔV) maximum, not to guarantee the security operation, especially diode load current diode with a high form factor. (Rate Mean Square)
If (RM): peak flow over periodic price allowed.
If (BC): The price of non periodic peak flows over the allowable
Q: Boundary integral diode current loading which is still able to experience it.
This scale applies to ½ cycles or 1 ms and a guide in the selection of surge protector.
Examples of data Fast Diode Type MF 70Maximum repetitive peak reverse voltage, Vdrm = 1200 Volt.Mean forward current, If (AV) = 70 ARMS forward current, IRMS max = 110 ANon repetitive forward current, If (ms) = 700 AForward V-Drop, VFM = V, the IFM = 210 APeak reverse current, IRM = 5 mAReverse recovery time, trr = 200 nsStored, charger, Qrr = T μc (Qs)Thermal resistance, Rth-jc = 0.37 ° C / w
At follow-up article will discuss: SCR (Silicon Controlled Rectifier), TRIAC (triode Alternating Current Switch), DIAC (Bilateral Trigger Diodes) and UJT (Uni-Transistor Juntion).
May be useful,

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