控制要求
调速：在一定的最高转速和最低转速范围内，分挡的（有级）或平滑的（无级）调节转速 稳速：以一定的精度在所需转速上稳定运行，在各种干扰下不允许有过大的转速波动，以确保产品质量 加、减速：频繁起、制动的设备要求加、减速尽量快，以提高生产率；不宜经受剧烈速度变化的机械则要求起，制动尽量平稳
基本术语
- 负载：电机在运行过程中所需克服的阻力，这种阻力需要电机输出相应的功率和扭矩来维持其运转
- 理想空载：这是指电机在没有任何负载的情况下运行时的情况。
- 额定负载：这是电机设计时假定的最大工作负载，电机在这个负载下可以安全稳定地运行。
调速指标
调速范围：电动机提供的最高转速和最低转速之比
D= \dfrac{n_{max}}{n_{min}} \end{align}$$ - $n_{max}$ 最高转速，在给定的电源和负载条件下能够达到的最大转速 - $n_{min}$ 最低转速，电机能够稳定运行的最小转速，通常在电机的额定负载下测量 **静差率**：描述电机在负载变化时转速稳定性的一个参数 在某一转速下运行时，负载由**理想空载**增加到**额定值**时所对应的**转速降落** $\Delta n_{N}$ 与**理想空载转速** $n_{0}$ 之比 $$\begin{align} s= \dfrac{\Delta n_{N}}{n_{0}} \end{align}$$ - $n_{0}$ 理想空载转速 - $n_{N}$ 额定负载下的转速 - $\Delta n_{N}=n_{0}-n_{N}$ 转速降落 对于同样硬度的特性，理想空载转速越低时，静差率越大，转速的相对稳定度也就越差 <svg xmlns="http://www.w3.org/2000/svg" version="1.1" viewBox="0 0 376.4089747803093 349.28016647526294" width="376.4089747803093" height="349.28016647526294"> <!-- svg-source:excalidraw --> <defs> <style class="style-fonts"> @font-face { font-family: "Virgil"; src: url("https://excalidraw.com/Virgil.woff2"); } @font-face { font-family: "Cascadia"; src: url("https://excalidraw.com/Cascadia.woff2"); } @font-face { font-family: "Assistant"; src: url("https://excalidraw.com/Assistant-Regular.woff2"); } </style> </defs> <rect x="0" y="0" width="376.4089747803093" 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21.44 C5.47 25.41, 4.03 29.38, 0 40.44" stroke="#1e1e1e" stroke-width="1" fill="none"></path></g></g><mask></mask></svg> **调速范围、静差率和额定速降之间的关系**：以最低速时所能达到的数值为准 $$\begin{align} & s= \dfrac{\Delta n_{N}}{n_{0min}}=\dfrac{\Delta n_{N}}{n_{min}+\Delta n_{N}} \\ & n_{min}=\dfrac{(1-s)\Delta n_{N}}{s} \\ & D= \dfrac{n_{max}}{n_{min}}=\dfrac{n_{N}s}{\Delta n_{N}(1-s)} \end{align}$$ - $n_{N}$ 为额定转速，也即最高转速 $n_{max}$ - $n_{min}$ 最低转速，在额定负载下电机实际运行的转速 - $n_{0min}$ 理想的空载转速（最低速要求下的） 没有负载的情况下电机的转速 $n_{0 min}=n_{min}+\Delta n_{N}$ - $\Delta n_{N}$ 转速降落 >[!important] 注意 > >调速范围和静差率这两项指标并不是彼此孤立的，必须同时提才有意义。 >调速系统的静差率指标应以最低速时所能达到的数值为准 >一个调速系统的调速范围，是指在最低速时还能满足所需静差率的转速可调范围 简单理解就是：在已知最低转速和额定转速时 最低转速由转速降落反过来得到（最低速要求下）的理想空载转速 用静差率表达最低转速 再最后得到调速范围和静差率的表达式 例题 额定转速 1000r/min, 额定速降 $\Delta n_{N}=100r/min$ 1. 要求静差率30%时，允许多大的调速范围 2. 要求静差率20%，则调速范围是多少 3. 调速范围达到10，所能满足的静差率是多少 $D=\dfrac{1000\times0.3}{100\times(1-0.3)}$ $D=\dfrac{1000\times 0.2}{100\times(1-0.2)}$ $s=\dfrac{D\Delta n_{N}}{n_{N}+D\Delta n_{N}}=\dfrac{10\times100}{1000+10\times 100}$ 需要调速的生产机械常常对静差率有一定的要求。在这些情况下，**开环调速系统**往往==不能满足要求== 考虑：[[直流电机的闭环调速系统\|闭环调速系统]]