20春学期《电机拖动》在线平时作业3

adminhan

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">机械特性曲线硬度好，表示电磁转矩有较大变化时，电机转速变化不大。（　）</span>
A:错误
B:正确

&nbsp; <p style="LINE-HEIGHT: 150%"><span style="LINE-HEIGHT: 150%; FONT-SIZE: 10.5pt">交流绕组短距系数是不大于<span lang="EN-US">1</span>的数值。（ 　）<span lang="EN-US"><o:p></o:p></span></span></p>
A:错误
B:正确

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-ascii-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">绕线式异步电动机转子回路串电阻越大，起动转矩越大，最大转矩也越大。（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"> </span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-ascii-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">　）</span>
A:错误
B:正确

&nbsp; <span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">他励直流电动机接线上与并励电动机相同，主磁极绕组与电枢绕组并联。（</span><span style="LINE-HEIGHT: 150%; mso-bidi-font-size: 10.5pt" lang="EN-US"><span style="mso-spacerun: yes">&nbsp; </span></span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">）</span><span style="LINE-HEIGHT: 150%; mso-bidi-font-size: 10.5pt" lang="EN-US"><br /></span>
A:错误
B:正确

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-ascii-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">三相异步电动机正常运行时，负载转矩增加，转差率增大。（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"> </span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-ascii-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">　）</span>
A:错误
B:正确

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">直流电机作为发电机运行时，电枢电动势</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA" lang="EN-US">E</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">与电枢电流</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA" lang="EN-US">I</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">的方向相反。（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"> <span style="mso-spacerun: yes">&nbsp;</span></span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">　）</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA" lang="EN-US"><br style="mso-special-character: line-break" /><br style="mso-special-character: line-break" /></span>
A:错误
B:正确

&nbsp; <p style="LINE-HEIGHT: 150%"><span style="LINE-HEIGHT: 150%; FONT-SIZE: 10.5pt">一相交流绕组通入正弦交流电产生旋转磁场。（　）<span lang="EN-US"><o:p></o:p></span></span></p>
A:错误
B:正确

&nbsp; <p style="LINE-HEIGHT: 150%" class="MsoNormal"><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-bidi-font-size: 10.5pt">短时工作制电动机在额定功率下的最高温升是电动机稳定温升（</span><span style="LINE-HEIGHT: 150%; mso-bidi-font-size: 10.5pt" lang="EN-US"><span style="mso-spacerun: yes">&nbsp;&nbsp;&nbsp; </span></span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-bidi-font-size: 10.5pt">）</span><span style="LINE-HEIGHT: 150%; mso-bidi-font-size: 10.5pt" lang="EN-US"><o:p></o:p></span></p>
A:错误
B:正确

&nbsp; <p style="LINE-HEIGHT: 150%" class="MsoNormal"><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">直流发电机电枢绕组产生的交流电动势经过换向器和电刷输出直流电。（</span><span style="LINE-HEIGHT: 150%; mso-bidi-font-size: 10.5pt"> <span style="mso-spacerun: yes">&nbsp;</span></span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-bidi-font-size: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">　）</span><span style="LINE-HEIGHT: 150%; mso-bidi-font-size: 10.5pt" lang="EN-US"><o:p></o:p></span></p>
A:错误
B:正确

&nbsp; <p style="LINE-HEIGHT: 150%"><span style="LINE-HEIGHT: 150%; FONT-SIZE: 10.5pt">异步电动机处于理想空载状态时转差率<span lang="EN-US">s=1</span>，起动时转差率<span lang="EN-US">s=0</span>。（ 　）<span lang="EN-US"><o:p></o:p></span></span></p>
A:错误
B:正确

&nbsp; <p style="LINE-HEIGHT: 150%"><span style="LINE-HEIGHT: 150%; FONT-SIZE: 10.5pt">异步电动机处于正向回馈状态时，转差率<span lang="EN-US">s&lt;0</span>。（ 　）<span lang="EN-US"><o:p></o:p></span></span></p>
A:错误
B:正确

&nbsp; <p style="LINE-HEIGHT: 150%"><span style="LINE-HEIGHT: 150%; FONT-SIZE: 10.5pt">交流绕组<span lang="EN-US">60</span>度相带的分布系数高于<span lang="EN-US">120</span>度相带的分布系数。（ 　）<span lang="EN-US"><o:p></o:p></span></span></p>
A:错误
B:正确

&nbsp; <p style="LINE-HEIGHT: 150%"><span style="LINE-HEIGHT: 150%; FONT-SIZE: 10.5pt">变压器所带容性负载增加，副边电压可能升高也可能下降。（<span lang="EN-US"><span style="mso-spacerun: yes">&nbsp; </span></span>）<span lang="EN-US"><o:p></o:p></span></span></p>
A:错误
B:正确

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">三相异步电动机旋转磁场转速与电源频率成正比，与电机极对数成反比。（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"> </span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">　）</span>
A:错误
B:正确

&nbsp; <p style="LINE-HEIGHT: 150%"><span style="LINE-HEIGHT: 150%; FONT-SIZE: 10.5pt">三相异步电动机以最大转矩起动，临界转差率为<span lang="EN-US">1</span>。（ 　）<span lang="EN-US"><o:p></o:p></span></span></p>
A:错误
B:正确

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">串励电机流过励磁绕组电流和流过电枢绕组电流相等。（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"> <span style="mso-spacerun: yes">&nbsp;</span></span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">　）</span>
A:错误
B:正确

&nbsp; <p style="LINE-HEIGHT: 150%" class="MsoNormal"><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-bidi-font-size: 10.5pt">标准的负载持续率分为</span><span style="LINE-HEIGHT: 150%; mso-bidi-font-size: 10.5pt" lang="EN-US">15%</span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-bidi-font-size: 10.5pt">，</span><span style="LINE-HEIGHT: 150%; mso-bidi-font-size: 10.5pt" lang="EN-US">25%</span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-bidi-font-size: 10.5pt">，</span><span style="LINE-HEIGHT: 150%; mso-bidi-font-size: 10.5pt" lang="EN-US">40%</span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-bidi-font-size: 10.5pt">和</span><span style="LINE-HEIGHT: 150%; mso-bidi-font-size: 10.5pt" lang="EN-US">60%</span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-bidi-font-size: 10.5pt">（</span><span style="LINE-HEIGHT: 150%; mso-bidi-font-size: 10.5pt" lang="EN-US"><span style="mso-spacerun: yes">&nbsp;&nbsp;&nbsp;&nbsp; </span></span><span style="LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-bidi-font-size: 10.5pt">）</span><span style="LINE-HEIGHT: 150%; mso-bidi-font-size: 10.5pt" lang="EN-US"><o:p></o:p></span></p>
A:错误
B:正确

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">直流电机具有可逆性。（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"> <span style="mso-spacerun: yes">&nbsp;</span></span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">　）</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA" lang="EN-US"><span style="mso-tab-count: 1">&nbsp; </span></span>
A:错误
B:正确

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">一台三相异步电动机，电源频率为</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA" lang="EN-US">50Hz</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">极对数是</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA" lang="EN-US">2</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">这台电动机的旋转磁场转速为</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA" lang="EN-US">3000</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">转</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA" lang="EN-US">/</span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">分。（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"> </span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">　）</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA" lang="EN-US"><br style="mso-special-character: line-break" /><br style="mso-special-character: line-break" /></span>
A:错误
B:正确

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">在变压器中由交变磁通产生的感应电动势，其正方向与产生该磁通的电流方向相反。（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-fareast-font-family: 宋体" lang="EN-US"><span style="mso-spacerun: yes">&nbsp; </span></span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">）</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-fareast-font-family: 宋体" lang="EN-US"><br style="mso-special-character: line-break" /><br style="mso-special-character: line-break" /></span>
A:错误
B:正确

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">气隙增大，电机磁路的磁阻也将增大。（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"> <span style="mso-spacerun: yes">&nbsp;</span></span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">　）</span>
A:错误
B:正确

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-ascii-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">常见的电动机工作制分为连续工作制、短时工作制和断续周期工作制（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA" lang="EN-US"><span style="mso-spacerun: yes">&nbsp;&nbsp; </span></span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-ascii-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">）</span>
A:错误
B:正确

<span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">同时改变直流电动机电枢两端和励磁两端电压极性，可以改变电机转向。（</span><span style="FONT-FAMILY: 'Times New Roman'; FONT-SIZE: 10.5pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"> <span style="mso-spacerun: yes">&nbsp;</span></span><span style="FONT-FAMILY: 宋体; FONT-SIZE: 10.5pt; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-bidi-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">　）</span>
A:错误
B:正确

&nbsp; <p style="LINE-HEIGHT: 150%"><span style="LINE-HEIGHT: 150%; FONT-SIZE: 10.5pt">交流电机通入交流电，所以电机转速不断变化；直流电机通入直流电，所以电机转速恒定。（　）<span lang="EN-US"><o:p></o:p></span></span></p>
A:错误
B:正确

&nbsp; <p style="LINE-HEIGHT: 150%"><span style="LINE-HEIGHT: 150%; FONT-SIZE: 10.5pt">起重机提升或下放同一重物时，传动机构损耗一样，但系统效率不一样。（　）<span lang="EN-US"><o:p></o:p></span></span></p>
A:错误
B:正确