Transformer action

If a greater reduction in line current is required for starting ac motors than is possible with reac tor starting, autotrausformers may be used. Because of transformer action, the reduction in motor-starting torque is directly proportional to the reduction in line current. Table 29-3 compares reactor and autotrausformer starting with respect to... 

Glass, J.M. Machiavelli s Prince alchemical transformation action archetype of regeneration. Polity 8, no. 4 (Summer 1976) 503-528. 

So far we have considered quantum systems. Similar considerations can be applied to classical systems and, in particular, to the classical Friedrichs model [13, 19]. In the A representation we have flucmations. We can define transformed action variables like in the quanmm case. 

Figure 1. Numerical result of the time evolution of the bare action J t) (solid line), and the transformed action /i (r) (dashed line) for times much smaller than the relaxation time. The bold dots are the result of applying A to J t) at several points in time—that is, the result of inverse transformation applied on points on the transformed dashed line.

Use aromatic herbs which have a unique dispersing and transforming action to penetrate the dampness in the Upper- and Middle-Jiao and eliminate it. 

The mechanism by which selenium retards virally induced tumorigenesis is unknown. Selenium may inhibit tumor formation by interfering with the replication or transforming action of viruses. Selenium may simply be reducing the proliferation of the transformed cells such that the presence of tumors is not detectable. 

Classic transformer action implies that the voltages across the windings of the transformer, and the currents through each of them, scale according to the turns ratio, as described in Figure 3-1. But it is perhaps not immediately apparent why the flyback inductor exhibits transformer action. 

Coming to the question of how currents actually reflect from one side of the transformer to the other, it must be pointed out that even though the final current scaling equations of a flyback transformer are exactly the same as in the case of an actual transformer, this is not strictly classic transformer action. The difference from a conventional transformer is, that in the flyback, the primary and secondary windings do not conduct at the same time. So in fact, it is a mystery why their currents are related to each other at all ... 

Summarizing, transformer action works as follows — when reflecting a voltage from primary to secondary side, we need to divide by the turns ratio. When going from the secondary to the primary side, we need to multiply by the turns ratio. The rule reverses for currents — so we multiply by the turns ratio when going from primary to secondary, and divide in the opposite direction. 

The magnetization current component is not coupled by transformer action to the secondary. In that sense, it is like a parallel leakage inductance. We need to subtract this component from the total switch current, and only then will we find that the primary and secondary currents scale according to the turns ratio. In other words, the magnetization current does not scale — it stays confined to the primary side. 

For various subtle reasons, like being able to ensure the transformer resets predictably under all conditions, and also for various production-related reasons, the number of turns of the tertiary winding is usually kept exactly the same as the primary winding. Therefore by transformer action, the voltage at the primary-side switching node (drain of the mosfet) must rise to 2 x Vin when the switch turns OFF. Therefore, in a universal-input off-line single-ended (i.e. single-switch) forward converter, we need a switch rated for at least 800 V. 

The transformer-based device shown in Figure 9-5 exploits the fact that common mode voltages cannot cause transformer action — because transformer action requires that a differential voltage be applied, so as to produce current in the windings, and thereby causes the flux to swing within the core. Unlike the LISN MATE, in this case both CM and DM noise components are outputted. This device used to be available from AEMC in France, at www.aemc.fr. 

When the emf is indnced in one winding by the current changing in a second winding the process is called indnction by transformer action or transformer induced emf. 

When two separate coiis are piaced ciose together, as they are in a transformer, a current in one coii produces a magnetic fiux which links with the second coil. This induces a voltage in the second coil and is the basic principle of the transformer action which is described later in this chapter. The two coils in this case are said to possess mutual inductance, as shown in Fig. 2.43. 

Various transformative actions are of vital importance for change, and it is possible to identify areas of transformative action that are crucial for change in the transformation of engineering education (UNESCO Report 2010 Beanland and Hadgraft 2013). These relate particularly to ... 

Inductive (magnetic) coupling employs the principles of transformer action. The efficiency of the coupling depends on three conditions ... 

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