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一台他励直流电动机，P_N=100kW，U_N=440V，I_N=254A，n_N=1000r/min，R_a=0.1Ω，容许最大电枢电流为2.2I_N，试求：1）若电机在额定工况下稳定运行于电动状态，现要求以最大电枢电流进行反接制动，所需的制动电阻为多大？2）若负载为位能性负载，且负载转矩T_L=0.8T_N，要使电动机以100r/min的转速下放货物，如何实现？求出相应参数。

它励直流电动机：P_N= 100 kW，U_N= 440 V，I_N= 254 A，n_N= 1000 r/min，R_a= 0.1 Ω，容许最大电枢电流I_a= 2.2 I_N，设电机带动额定负载以额定转速稳定运行在电动状态，试求： 1）以最大电枢电流进行反接制动时，所需制动电阻为多大？ 2）如负载为位能性负载，要使电机以100 r/min的速度下放重物，如何实现？求出相应参数； 3）画出固有特性示意图及上述（1）、（2）两种情况的机械特性示意图。

He is rather ________ in his daily life.

John complained to the book seller that there were several pages _______ in the dictionary.

---It’s rather cold in here. Do you mind if I close the window? ---____________.

There is no _________ in the world.

Farmers ____ by government to do odd jobs in cities when they are free.

But for their help，we         the program in time

I have been busy working for a long time so I need to ______ in this National Day Holiday and enjoy time.

The thief admitted _______ gold rings in the store