Application And Study On Fault Excitation Device With Constant Power For Model DF₇ Diesel Locomotive

With the rapid development of railway innovation, the applicable quality of locomotives has placed a greater and greater effect on the railway transportation order. Since 1996 the model DF_7D internal-combustion engine has been qualified to play a major in the traction mission for the Qian-Gui route, although during that period it was taken into account the fact that there was a need to better equip the locomotive with a hitch emergency system: the so-called hitch excitation device, however, the design itself has its own limitation. That is, no matter the diesel engine works under how great rotate speed, the excitation current of the major dynamo always keeps constant. Therefore, making it difficult for such current-constant control to eventually ensure power of the AC synchronous dynamo to be kept as constant as possible. As a result, hardly the design can fully exert the power of diesel engine, nor can it satisfy the requirement of locomotive traction. Because there is so far no better ways to track down such problem, therefore the development of normal railway transportation order is greatly affected.The design purpose of hitch power-constant excitation device is to make use of existing and credible signals as much as possible. The hardware architecture of the device is made of mainframe, voltage sensor and current sensor. The architecture itself is not only simple, but also of high degree of reliability. Its basic principle is to make output of the diesel engine be constant and satisfy the needs of locomotive traction by making the synchronous dynamo to be current changing controlled. Its basic rationale is: On one hand to change the rotate speed signal of diesel engine to module rotate speed signal by using the F/V frequency converter in order to obtain the curve function Pref=f(n). On the other hand to get the output power of the AC sync dynamo by multiplying both the output voltage and the current of AC sync dynamo. At last, output the Vp intermediate signal and control the output of the VMOS tube by actively comparing both the specified power signal and the feedback power signal P in order to achieve the aim of implementing the current changing excitation control of sync traction dynamo, make sure the power output of the diesel engine to be constant, and satisfy the requirement of traction of locomotives.