一次习题课(变压器和直流电机)(版).pptVIP

3. Inserting a resistor in series with the armature circuit 电枢回路串电阻调速（因为损耗大，故较少采用） The effect of armature resistance speed control on a shunt dc motor’s torque-speed characteristic Look at the figure 7-13 on the page 399 十、 The series dc motors 串励电动机 P408 1、 The torque-speed characteristic of a series dc motor Never completely unload a series motor, and never connect one to a load by a belt or other mechanism that could break.串励电动机不能空载运行。(P411) 十一、 Dc motor starter 直流电动机启动器P418 直接额定电压起动有何问题？如何解决？ 十二、 直流发电机的5种类型 Separately excited dc generator他励式发电机 Shunt dc generator 并励式发电机 Series dc generator 串励式发电机 Cumulatively compound dc generator 积复励发电机 Differentially compound dc generator 差复励发电机 十三、 The terminal characteristic of a separately excited generator— a plot of VT versus IL for a constant ω For generators with compensating windings 电压调整特性 如何实现直流发电机的“稳压”？ 调节励磁 十四、 Control of terminal voltage of a separately excited generator 2.Changing the field current IF 1.Changing the speed of rotationω 十五、Three conditions required for voltage buildup 并励直流发电机的自励条件P450 Residual magnetic flux 电机主磁路有剩磁通 If not, the solution is：disconnect the field from the armature circuit and connect it directly to an external dc source such as a battery. EA,res produces a field current which produces a flux adding the residual flux. EA,res产生的磁通与剩磁通同向 If not, the solution is ：reversing the direction of the rotation or by reversing the field connections. RF is smaller than the critical resistance RF 小于临界起压电阻 If not, the solution is ：reducing RF 十六、 The terminal characteristic of a shunt dc generator Field weakening effect 如何实现直流发电机的“稳压”？ 调节励磁 十七、一些习题练习 1、某台直流电动机： 求（1）额定的输入功率（2）额定电流（3）额定转矩 解（1）额定的输入功率 解（2）额定电流 解（3）额定转矩 2、某台直流发电机： 求额定电流 因为是发电机，故额定功率是额定的输出电功率，额定电压是额定的输出电压，而额定电流是额定的输出电流 3、某台并励直流发电机： 求额定运行时：(1)电磁功率(即转换功率)（2）电磁转矩 解:因为是并励发电机，故发电机的电枢电流等于输出电流与励磁电流之和。 3、某台并励直流发电机： 求额定运行时：(1)电磁功率(即转换功率)（2）电磁转矩 解:因为是并励发电机，故发电机的电枢电流等于输出电流与励磁电流之和。 4、某台并励直流发电机的电磁功率(转换功率)与输出功率之差为 （1）励磁损耗与铜耗之和（2）铁耗与杂散损耗之和 （3）铁耗、