Question

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Even though half of the possible harmonic frequencies are eliminated by the typically symmetrical distortion of nonlinear loads, the odd harmonics can still cause problems. Some of these problems are general to all power systems, single-phase or otherwise. Transformer overheating due to eddy current losses, for example, can occur in any AC power system where there is significant harmonic content. However, there are some problems caused by harmonic currents that are specific to polyphase power systems, and it is these problems to which this section is specifically devoted.
It is helpful to be able to simulate nonlinear loads in SPICE so as to avoid a lot of complex mathematics and obtain a more intuitive understanding of harmonic effects. First, we'll begin our simulation with a very simple AC circuit: a single sine-wave voltage source with a purely linear load and all associated resistances
The Rsource and Rline resistances in this circuit do more than just mimic the real world: they also provide convenient shunt resistances for measuring currents in the SPICE simulation: by reading voltage across a 1 Ω resistance, you obtain a direct indication of current through it, since E = IR.
A SPICE simulation of this circuit with Fourier analysis on the voltage measured across Rline should show us the harmonic content of this circuit's line current. Being completely linear in nature, we should expect no harmonics other than the 1st (fundamental) of 60 Hz, assuming a 60 Hz source

Answer 1

虽然可能的泛音频率的一半被非线性装载的典型对称畸变消灭, 奇怪的泛音可能仍然造成问题。这些问题是一般的对所有动力系统, 单阶段或否则。变压器过度加热由于漩涡潮流损失, 例如, 可能发生在有重大泛音内容的任一个交流电能系统。但是, 有一些问题由是具体的对多相的动力系统的泛音潮流造成, 并且这是这个部分是具体地献身的这些问题对。它是有用能模仿非线性装载在香料里以便避免很多复杂数学和获得对泛音作用的更加直觉的理解。首先, 我们从一条非常简单的AC 电路将开始我们的模仿: 唯一正弦挥动电压来源以纯净地线性装载并且所有伴生的抵抗Rsource 和Rline 抵抗在这条电路里做更多比仿造现实世界: 他们为测量的潮流并且提供方便分流器抵抗在香料模仿: 由读的电压横跨1? 抵抗, 您获得潮流的一个直接征兆通过它, 从E = IR 。这条电路的香料模仿以傅立叶分析在电压测量了横跨Rline 应该显示我们这条电路的线潮流泛音内容。是完全地线性在自然里, 我们不应该期望泛音不同于1 (根本性) 60 赫兹, 承担一个60 赫兹来源