Primary turns

Suppose 10,000 V, j (e.g., from an electrical power plant generator) is input to a transformer where the number of secondary turns is 75 times more than the number of primary turns. Then the voltage from the secondary will be 75 X 10,000 = 750,000... 

So even with no information about the permeability of the material, air gap, and so on, we already know the number of turns required on a core with area Ae that will produce a certain B-field. We also know that with or without an air gap, the B-field should not exceed 0.3 T for most ferrites. So solving the equation for N (N is np here, number of primary turns),... 

Note also that the duty cycle of such a forward converter can under no circumstances ever be allowed to exceed 50%. The reason for that is we have to unconditionally ensure that transformer reset will always occur, every cycle. Since we have no direct control on the transformer current waveforms, we have to just leave enough time for the current in the tertiary winding to ramp down to zero on its own. In other words, we have to allow voltseconds balance to occur naturally in the transformer. However, because the number of turns in the tertiary winding is equal to the primary turns, the voltage across the tertiary winding is equal to Vin when the switch is ON, and is also equal to Vin (opposite direction) when the switch is OFF. Reset will therefore occur when toFF becomes equal to toN- So, if the duty cycle exceeds 50%, toN would certainly always exceed toFF, and therefore transformer reset would never be able to occur. That would eventually destroy the switch. Therefore, just to allow toFF to be large enough, the duty cycle must always be kept to less than 50%. 

Note that this could have turned out to be significantly different from an integer. In that case, we would round it off to the nearest (higher) integer, and then recalculate the primary turns, the new flux density swing, and the core loss — similar to what we did for the flyback. But at the moment, we can simply use... 

Vp = the primary voltage /s = the secondary voltage Np = the number of primary turns Ns = the number of secondary turns... 

A 230V to 12V emergency lighting transformer is constructed with 800 primary turns. Calculate the number of secondary turns required. Collecting the information given in the question into a usable form, we have ... 

A plectonemic supercoil obtained by removing positive primary turns is a negative super coil although the direction of the primary DNA helix is right handed. Conversely, a plectonemic supercoil obtained by the addition of positive turns or overwinding is a positive supercoil although the DNA helix is left handed. 

A primary class of additives is that of the detergents. We will examine in turn the role they play in motor fuels and the chemical structures that are necessary. 

Primary aromatic amides are crystaUine sohds with definite melting points. Upon boiling with 10-20 per cent, sodium or potassium hydroxide solution, they are hydrolysed with the evolution of ammonia (vapour turns red htmus paper blue and mercurous nitrate paper black) and the formation of the alkah metal salt of the acid ... 

Methane. The largest use of methane is for synthesis gas, a mixture of hydrogen and carbon monoxide. Synthesis gas, in turn, is the primary feed for the production of ammonia (qv) and methanol (qv). Synthesis gas is produced by steam reforming of methane over a nickel catalyst. 

Radiation Damage. It has been known for many years that bombardment of a crystal with energetic (keV to MeV) heavy ions produces regions of lattice disorder. An implanted ion entering a soHd with an initial kinetic energy of 100 keV comes to rest in the time scale of about 10 due to both electronic and nuclear coUisions. As an ion slows down and comes to rest in a crystal, it makes a number of coUisions with the lattice atoms. In these coUisions, sufficient energy may be transferred from the ion to displace an atom from its lattice site. Lattice atoms which are displaced by an incident ion are caUed primary knock-on atoms (PKA). A PKA can in turn displace other atoms, secondary knock-ons, etc. This process creates a cascade of atomic coUisions and is coUectively referred to as the coUision, or displacement, cascade. The disorder can be directiy observed by techniques sensitive to lattice stmcture, such as electron-transmission microscopy, MeV-particle channeling, and electron diffraction. 

For the measurement of magnetisation in hysteresis-loop measurements, a search coil consisting of several-turn windings around a specimen is coimected to a fluxmeter whose output can be recoded on thejy-axis of an x,y plotter. The x-axis records the field strength of the primary coil around the specimen. The whole procedure can be done conveniendy in a hysteresigraph, whereby the induction is recorded automatically as the field is varied continuously. 

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