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The main differences between domestic and industrial fuses are the nominal
voltage and current levels (which require much larger physical dimensions) and
their fault-current breaking capabilities. Type gG fuse-links are often used for the
protection of motor circuits, which is possible when their characteristics are capable
of withstanding the motor-starting current without deterioration.
A more recent development has been the adoption by the IEC of a fuse-type gM for
motor protection, designed to cover starting, and short-circuit conditions. This type of
fuse is more popular in some countries than in others, but at the present time the
aM fuse in combination with a thermal overload relay is more-widely used.
A gM fuse-link, which has a dual rating is characterized by two current values. The
first value In denotes both the rated current of the fuse-link and the rated current of
the fuseholder; the second value Ich denotes the time-current characteristic of the
fuse-link as defined by the gates in Tables II, III and VI of IEC 60269-1.
These two ratings are separated by a letter which defines the applications.
For example: In M Ich denotes a fuse intended to be used for protection of
motor circuits and having the characteristic G. The first value In corresponds to
the maximum continuous current for the whole fuse and the second value Ich
corresponds to the G characteristic of the fuse link. For further details see note at the
end of sub-clause 2.1.
An aM fuse-link is characterized by one current value In and time-current
characteristic as shown in Figure H14 next page.
Important: Some national standards use a gI (industrial) type fuse, similar in all main
essentails to type gG fuses.
Type gI fuses should never be used, however, in domestic and similar installations.
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What is transconductance?
Conductance is the reciprocal of resistance. If it is taken between one output parameter and one input parameter, then it is called transconductance i. e. the ratio of output current to the input voltage.It is given by gm= Iout/Vin
What is the inverse of transconductance?
Roughly speaking, resistance. Transconductance refers to the reciprocal of the amplifying device's internal resistance. The concept is particularly useful if the device is a voltage-controlled current source (tube or FET). In vacuum tube amplifiers, transconductance (Gm) is (u / Rp), where... u is the amplification factor. u= (Gm x Rp). Rp is the anode (drain) resistance. Rp is the internal resistance of the amplifying device. Gfs is synonymous with Gm. The reciprocal of Gm (or Gfs) is (Rp / u). Another term for this reciprocal is transresistance.
What is the re-model of npn common base transistor?
Thus if we go back to the circuit model for the common emitter transistor, and re-draw it as a small signal model it would look something like Figure 1. Here we have replaced the diode with a linear element (a resistor, called rπ) and we have changed the notation for the currents from IB and IC to ib and ic respectively, to remind us that we are now talking about small signal ac quantities, not large signal ones. The bias currents IB and IC are still flowing through the device (and we will leave it to ELEC 342 to discuss how these are generated and set up) but they do not appear in the small signal model. This model is only used to figure out how the transistor behaves for the ac signal going through it, not have it responds to large DC values. Figure 1: Small signal linear model for the common emitter transistor Figure 1 (3.16.png) Now rπ the equivalent small signal resistance of the base-emitter diode is given simply by the inverse of the conductance of the equivalent diode. Remember, we found rπ===1qkTIB1qkTICββ40IC (1) where we have used the fact that IC=βIB and qkT=40V-1. As we said earlier, typical values for βin a standard bipolar transistor will be around 100. Thus, for a typical collector bias current of IC=1mA, rπ will be about 2.5 kΩ. There is one more item we should consider in putting together our model for the bipolar transistor. We did not get things completely right when we drew the common emitter characteristic curves for the transistor. There is a somewhat subtle effect going on when VCE is increased. Remember, we said that the current coming out of the collector is not effected by how big the drop was in the reverse biased base-collector junction. The collector current just depends on how many electrons are injected into the base by the emitter, and how many of them make it across the base to the base-collector junction. As the base-collector reverse bias is increased (by increasing VCE the depletion width of the base-collector junction increases as well. This has the effect of making the base region somewhat shorter. This means that a few more electrons are able to make it across the base region without recombining and as a result α and hence β increase somewhat. This then means that IC goes up slightly with increasing VCE. The effect is called base width modulation. Let us now include that effect in the common emitter characteristic curves. As you can see in Figure 3, there is now a slope to the IC(VCE) curve, with IC increasing somewhat as VCE increases. The effect has been somewhat exaggerated in Figure 2, and I will now make the slope even bigger so that we may define a new quantity, called the Early Voltage. Figure 2: Common emitter response with base-width modulation effectFigure 2 (3.17b.png) Figure 3: Finding the Early VoltageFigure 3 (3.18b.png) Back in the very beginning of the transistor era, an engineer at Bell Labs, Jim Early, predicted that there would be a slope to the IC curves, and that they would all project back to the same intersection point on the horizontal axis. Having made that prediction, Jim went down into the lab, made the measurement, and confirmed his prediction, thus showing that the theory of transistor behavior was being properly understood. The point of intersection of the VCE axis is known as the Early Voltage. Since the symbol VE, for the emitter voltage was already taken, they had to label the Early Voltage VA instead. (Even though the intersection point in on the negative half of the VCE axis, VA is universally quoted as a positive number.) How can we model the sloping I-V curve? We can do almost the same thing as we did with the solar cell. The horizontal part of the curve is still a current source, and the sloped part is simply a resistor in parallel with it. Here is a graphical explanation in Figure 4. Figure 4: Combining a current course and a resistor in parallelFigure 4 (3.19.png) Usually, the slope is much less than we have shown here, and so for any given value of IC, we can just take the slope of the line as ICVA, and hence the resistance, which is usually called ro is just VAIc. Thus, we add ro to the small signal model for the bipolar transistor. This is shown in Figure 5. In a good quality modern transistor, the Early Voltage, VA will be on the order of 150-250 Volts. So if we let VA=200, and we imagine that we have our transistor biased at 1 mA, then ro==200V1mA200kΩ (2) which is usually much larger than most of the other resistors you will encounter in a typical circuit. In most instances, ro can be ignored with no problem. If you get into high impedance circuits however, as you might find in a instrumentation amplifier, then vbe has to be taken into account. Figure 5: Including ro in the small signal linear modelFigure 5 (3.20.png) Sometimes it is advantageous to use a mutual transconductance model instead of a current gain model for the transistor. If we call the input small signal voltage vbe, then obviously ib==vberπvbeβ40IC (3) But ic=βib=βvbeβ40IC=40ICvbe≡gmvbe (4) Where gm is called the mutual transconductance of the transistor. Notice that β has completely cancelled out in the expression for gm and that gm depends only upon the bias current, IC, flowing through the collector and not on any of the physical properties of the transistor itself! Figure 6: Transconductance small signal linear modelFigure 6 (3.21.png) Finally, there is one last physical consideration we should make concerning the operation of the bipolar transistor. The base-collector junction is reverse biased. We know that if we apply too much reverse bias to a pn junction, it can breakdown through avalanche multiplication. Breakdown in a transistor is somewhat "softer" than for a simple diode, because once a small amount of avalanche multiplication starts, extra holes are generated within the base-collector junction. These holes fall up, into the base, where they act as additional base current, which, in turn, causes IC to increase. This is shown in Figure 7. Figure 7: Ionization at the base-collector junction causes additional base currentFigure 7 (3.22.png) A set of characteristic curves for a transistor going into breakdown is also shown in Figure 8. Figure 8: Bipolar Transistor going into breakdownFigure 8 (3.23b.png) Well, we have learned quite a bit about bipolar transistors in a very short space. Go back over this chapter and see if you can pick out the two or three most important ideas of equations which would make up a set of "facts" that you could stick away in you head someplace. Do this so you will always have them to refer to when the subject of bipolars comes up (In say, a job interview or something!).
IS CODE for transformer oil?
Refer to:International Electrotechnical Commission IEC 836"Specifications for silicone liquid for electrical purposes" (Silicone Fluid Type T-1) andASTM D 4652 "Silicone Fluids for Electrical Insulation" specifications for repair or top-off of existing liquid-filled units.These standards cover both the physical and electrical properties of fluid suitable for dielectric applications.Also refer following:IS-335/1993 - Specification for uninhibited new insulating oils.IS-12463/1988 - Specification for inhibited mineral insulating oils.IEC -60296/2003 - Specification for unused mineral insulating oils for transformers and switchgear. This standard cover both uninhibited and inhibited oils.ASTM - D3487/2000-StandardSpecification for Mineral Insulating Oil used in Electrical apparatus. This standard also covers both uninhibited and inhibited oils.Unused Mineral Insulating oils filled inNew transformersIS -1866/2000-Code of Practice for Electrical Maintenance and supervision of Mineral Insulating oil in Equipment. (Refer Table.1 for limiting values of various parameters)IEC -60422/1998-Supervision and maintenance guide for mineral insulating oils in electrical equipment.In service Mineral Insulating oils:IS -1866/2000 -Code of Practice for Electrical Maintenance and supervision of Mineral Insulating oil in Equipment.(Refer Table for limiting values of various parameters)IS-335/1993Appearance ------------ Clear and transparentDensity at 29.5 deg.C (Max) 0.89 g/cm2Kinematic Viscosity (Max)1) at 27deg.C ------------------ 27 cSt2) at 40deg.C ------------------ Under considerationIFT at 27deg.C (Min) ---------0.04 N/mFlash Point (Min) --------- 140deg.CPour Point (Max) ---------- 6deg.CNeutralization Value1) Total Acidity (Max) ---- 0.03 mg KOH/gm2) Inorganic acidity ------ NilCorrosive Sulphur ------- Non-corrosiveElectric Strength (BDV)1) New unfiltered Oil (Min) 30 KV (rms)2) After filteration (Min) If the above value is not attained, the oil shall be filtered to 60 KV (rms)Dielectric dissipation factor (tan ) at 90deg.C(max) 0.002Specific resistance (Resistivity)1) at 90deg.C (Min) 35 x 10 12 ohm-cm2) at 27deg.C (Min) 1500 x 10 12 ohm-cmOxidation Stability1) Acidity (max) 0.4 mg KOH/gm2) total sludge (max) 0.1 % by weightAgeing characteristicsa) Resistivity (Min)1) at 27deg.C 2.5 x 10 12 ohm-cm2) at 90deg.C 0.2 x 10 12 ohm-cmb)Tanδ at 90deg.C (Max) 0.20c) Total acidity (Max) 0.05 mg KOH/gmd) Total sludge (Max) 0.05 % by weightPresence of Oxidation inhibitor -The oil shall contain natural anti oxidant additives.Water content - 50 ppmS K value - Under considerationIS-1866/2000-Recommended Limits of Unused Mineral Oil filled in NewTransformerPropertyHighest Voltage of Equipment (KV)< 72.572.5-170>170AppearanceClear, free from sediment and suspended matterDensity at 29.5 deg.C (g/cm2), Max.0.890.890.89Viscosity at 27 deg C (cst), Max272727Flash Point deg. C, Min140140140Pour Point Deg. C , Max-6-6-6Total acidity (mg KOH/gm), Max0.030.030.03Water Content (ppm), Max201510IFT at 27 degC,(mN/m), min353535Tanδ at 90 deg C, Max0.0150.0150.01Resistivity at 90 deg.C (x10e12 ohm cm Min.666BDV Kv Min405060IS-1866/2000-Violation Limits for in service oilsPropertyHighest Voltage of Equipment (KV)< 72.572.5-170>170Flash Point deg. C, MinMaximum decrease of 15deg.C from initial valuePour Point Deg. C , Max-6-6-6Total acidity (mg KOH/gm), Max0.30.30.3Water Content (ppm), MaxNo free water4020IFT at 27 degC, (mN/m), min111Tanδ at 90 deg C, Max110.2Resistivity at 90 deg.C (x10e12 ohm cm Min.111BDV Kv Min304050Sediment and SludgeNo sediment or precipitable sludge should be detected.Results below 0.02% by mass may be neglectedIS-1866/2000 - Frequency of testingPropertyFrequency of TestingAppearanceIn conjunction with other Quantitative testsWater contentAfter filling or refilling prior to energizing, then afterthree and 12 months, subsequently along with DGABDVAfter filling or refilling prior to energizing, then yearlyTotal acidityYearlyIFTAfter filling or refilling prior to energizing, then yearlyResistivityAfter filling or refilling prior to energizing, then yearlyTanδAfter filling or refilling prior to energizing, then yearlyFlash PointYearlySediment and sludgeYearlyIS-1866/2000-Recommended ActionsPropertyRecommended ActionsAppearanceAs dictated by other testsWater contentCheck Source of water and consider reconditioningBDVRecondition the oil or alternatively, if more economical or other tests dictate replace oilTotal acidityReplace or reclaim oilIFTReplace or reclaim oilResistivityReplace or reclaim oilTanδReplace or reclaim oilFlash PointReplace the oil, equipment may require inspectionSediment and sludgeWhere sediment is detected recondition the oilIS-1866/2000 - Classification of oils in service.Group 1:This group contains oils that are in satisfactory condition for continued use. The frequency can be followed as described earlier.Group 2:This group contains oils that requires reconditioning for further service. (LOW BDV and High water content). The frequency can be followed as described earlier after reconditioning.Group 3:This group contains oils in poor condition that it can restore satisfactory properties only after reclaiming. Insulating oils this group should be reclaimed or replaced depending on economic considerations.Group 4:This group contains oils, in such poor state that it is technically advisable to dispose of them.IEC -60296 - General SpecificationFunctional Properties: Viscosity, Pour point, Water content, BDV, Density, Tan.Stability Properties: Appearance, Acidity, IFT, corrosive Sulfur, Antioxident additivePerformance Properties: Oxidation Stabillity, SludgeHSE Properties: Flash Point, PCB content, PCA contentAshokHead Engineering & Project ExecutionEVI, INDIA
EEG?
DefinitionAn electroencephalogram (EEG) is a test to detect problems in the electrical activity of the brain.Alternative NamesElectroencephalogram; Brain wave testHow the test is performedBrain cells communicate with each other by producing tiny electrical impulses. In an EEG, this faint electrical activity is measured by putting electrodes on the scalp.The test is performed by an EEG technician in your health care provider's office, at a hospital, or at an independent laboratory. You will be asked to lie on your back on a bed or in a reclining chair.The technician will apply between 16 and 25 flat metal disks (electrodes) in different positions on your scalp. The disks are held in place with a sticky paste. The electrodes are connected by wires to an amplifier and a recording machine.The recording machine converts the electrical impulses into patterns that can be seen on a computer screen, as well as stored on a computer disk. Before computers, the activity was printed on paper. In either case, the electical activity looks like a series of wavy lines. You will need to lie still with your eyes closed because any movement can alter the results.You may be asked to do certain things during the recording, such as breathe deeply and rapidly for several minutes or look at a bright flashing light.How to prepare for the testYou will need to wash your hair the night before the test. Do not use any oils, sprays, or conditioner on your hair before this test.Your health care provider may want you to stop taking certain medications before the test. Do not change or stop medications without first talking to your health care provider.You should avoid all foods containing caffeine for 8 hours before the test.Sometimes it is necessary to sleep during the test, so you may be asked to reduce your sleep time the night before. If you're asked to sleep as little as possible before the test, don't consume any caffeine, energy drinks, or other products that help you stay awake.How the test will feelThis test causes no discomfort. Although having electrodes pasted onto your skin may feel strange, they only record activity and do not produce any sensation. No significant electricity passes from the electrode into your skin.Why the test is performedEEG is used to help diagnose if you're having seizures and if so, what type. An EEG is also used to find the causes of confusion, and to evaluate head injuries, tumors, infections, degenerative diseases such as Alzheimer's disease, and abnormal changes in body chemistry that affect the brain.It is also used to:Evaluate problems with sleep ( sleep disorders)To investigate periods of unconsciousnessTo monitor the brain during brain surgeryThe EEG may be done to show that the brain has no activity, in the case of someone in a deep coma. It can be helpful when trying to decide if someone is brain dead.EEG cannot be used to measure intelligence.Normal ValuesBrain electrical activity has certain frequencies (the number of waves per second) that are normal for different levels of consciousness. For example, brain waves are faster when you are awake, and slower when you're sleeping. There are also normal patterns to these waves. These frequencies and patterns are what the EEG reader looks for.What abnormal results meanAbnormal results on an EEG test may be due to:An abnormal structure in the brain (such as a brain tumor)Attention problemsTissue death due to a blockage in blood flow (cerebral infarction)Drug or alcohol abuseHead injuryInflammation of the brain (encephalitis)Hemorrhage (abnormal bleeding caused by a ruptured blood vessel)Migraines (in some cases)Seizure disorder (such as epilepsy or convulsions)Sleep disorder (such as narcolepsy)Note: A normal EEG does not mean that a seizure did not occur.What the risks areThe procedure is very safe. However, the flashing lights or fast breathing (hyperventilation) required during the test may trigger seizures in those with seizure disorders. The health care provider performing the EEG is trained to take care of you if this happens.It may be difficult to get the paste out of your hair, but it should come out after a few washings with regular shampoo.ReferencesTrescher WH, Lesser RP. The Epilepsies. In: Bradley WG, Daroff RB, Fenichel GM, Jankovic J, eds. Neurology in Clinical Practice. 5th ed. Philadelphia, Pa: Butterworth-Heinemann; 2008:chap 71.Krumholz A, Wiebe S, Gronseth G, et al. Practice parameter: evaluating an apparent unprovoked first seizure in adults (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology and the American Epilepsy Society. Neurology. 2007;69(21):1991-2007.
What is a national party?
KHGEDlkheg/gg,/GM"lgmM
What it means in a fuse ratinsg gG?
Its just for general purpose fuse. Comes from the german word Niederspannungs Hochleistungs which means low-voltage,high performance. Hah dont know if that helps much. gM fuses are used for motors
What is the Difference between mg and gm in pills?
There are 1000mg in a gram.
What is the difference between a troy ounce and an AVDP ounce?
Troy ounce is 31.103 gm. Avdp is 28.345 gm.
What is the difference between the 3800 series 2 and 3800 series 3 gm engine?
About 20hp.
Different between GM ford power steering fluid?
The difference between GM and Ford power steering fluid is in their chemical composition. Both have unique blends designed to work best in their equipment.
What is the difference between a Ls1 and a Z28?
LS1 is a GM engine, Z/28 is (was) an option package on Camaros.
Gm delco CD radio will not eject?
Sometimes the unit will reset itself if you pull the fuse out for a minute then reinstall the fuse.
What is the difference between 1996 and a 1995 5.7 gm?
In the 95 1/2 gm changed their truck motors from Throttle body ingection to multi port ingection. Thiis is due to the new regulations for vechicles.
What is the difference between 500MG and 1GM in pills?
500 MG (Miligrams) < 1 GM (grams)= 1000 MG (Miligrams) Hope this helps.
If Robert weighs 980 neutons what is his mass?
F = m Gm = F/GG = acceleration of gravity = 9.8 meters/sec2m = 980/9.8 = 100 kg
Is there a difference in the block heads of a 1971 gm 350 and 2000 gm 350?
Yes, they are very different.
