變壓器外文翻譯-其他專業(yè)(編輯修改稿)
2025-02-24 08:11 本頁(yè)面
【文章內(nèi)容簡(jiǎn)介】 8） or VpIp primary PF = VsIs secondary PF （ 39） where PF is the power factor. For the abovestated assumption it means that the power factor on primary and secondary sides are equal。 therefore VpIp = VsIs （ 310） from which is obtained psVV = psII ≌ psEE ≌ a （ 311） It shows that as an approximation the terminal voltage ratio equals the turns ratio. The primary and secondary current, on the other hand, are inversely related to the turns ratio. The turns ratio gives a measure of how much the secondary voltage is raised or lowered in relation to the primary voltage. To calculate the voltage regulation, we need 河南理工大學(xué)畢業(yè)設(shè)計(jì)（論文）說明書 VI more information. The ratio of the terminal voltage varies somewhat depending on the load and its power factor. In practice, the transformation ratio is obtained from the nameplate data, which list the primary and secondary voltage under fullload condition. When the secondary voltage Vs is reduced pared to the primary voltage, the transformation is said to be a stepdown transformer: conversely, if this voltage is raised, it is called a stepup transformer. In a stepdown transformer the transformation ratio a is greater than unity (a), while for a stepup transformer it is smaller than unity (a). In the event that a=1, the transformer secondary voltage equals the primary voltage. This is a special type of transformer used in instances where electrical isolation is required between the primary and secondary circuit while maintaining the same voltage level. Therefore, this transformer is generally knows as an isolation transformer. As is apparent, it is the magic flux in the core that forms the connecting link between primary and secondary circuit. In section 4 it is shown how the primary winding current adjusts itself to the secondary load current when the transformer supplies a load. Looking into the transformer terminals from the source, an impedance is seen which by definition equals Vp / Ip. From 311, we have Vp = aVs and Ip = Is/ terms of Vs and Is the ratio of Vp to Ip is ppVI = /ssaVIa = 2ssaVI （ 312） But Vs / Is is the load impedance ZL thus we can say that Zm (primary) = a2ZL （ 313） This equation tells us that when an impedance is connected to the secondary side, it appears from the source as an impedance having a magnitude that is a2 times its actual value. We say that the load impedance is reflected or referred to the primary. It is this property of transformers that is used in impedancematching applications. 4. TRANSFORMERS UNDER LOAD The primary and secondary voltages shown have similar polarities, as indicated by 河南理工大學(xué)畢業(yè)設(shè)計(jì)（論文）說明書 VII the “dotmaking” convention. The dots near the upper ends of the windings have the same meaning as in circuit theory。 the marked terminals have the same polarity. Thus when a load is connected to the secondary, the instantaneous load current is in the direction shown. In other words, the polarity markings signify that when positive current enters both windings at the marked terminals, the MMFs of the two windings add. Since the secondary voltage depends on the core flux φ0, it must be clear that the flux should not change appreciably if Es is to remain essentially constant under normal loading conditions. With the load connected, a current Is will flow in the secondary circuit, because the induced EMF Es will act as a voltage source. The secondary current produces an MMF NsIs that creates a flux. This flux has such a direction that at any instant in time it opposes the main flux that created it in the first p
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