Research and development of using ultra-large capacity capacitors to improve the electric starting performance of diesel locomotives for diesel locomotives Li Kai (Beijing Railway Bureau, Beijing 100860), the working principle of vehicle starting, analyzes the economic benefits of starting auxiliary devices, and tests the electric starting of diesel locomotives. It is confirmed that the use of ultra-large capacity capacitors to assist the battery to start the diesel generator set is technically feasible and has obvious benefits.
1 Overview At present, domestic diesel locomotives use battery packs to start diesel generator sets without using other auxiliary devices. The battery pack has problems such as long charging time, short life, high operation and maintenance costs, and environmental pollution.
If a capacitor is used as an auxiliary device for electric starting, these problems can be well solved and the performance of the electric starting can be improved; however, the capacity of the conventional capacitor cannot satisfy the requirements of the battery pack of the diesel locomotive. In the 1980s, Japan began to produce ultra-large capacity capacitors. The capacitor is made of activated carbon ultra-microporous fiber material and has a high technical content. It has been mass-produced only in a few countries such as Russia, the United States, and Japan, and has been successfully applied to the electric start of the diesel locomotive generator set. In recent years, domestically developed ultra-large capacity capacitors, whose performance is close to the international level, and the price is only one-third of the foreign products, which has created a good domestic diesel locomotive using ultra-large capacity capacitors as electric starting aids. condition.
2 Capacitor assists the working principle of the electric start of the diesel locomotive The principle of using the ultra-large capacity capacitor as the electric start assisting device of the diesel locomotive is as shown. The original starting device includes battery pack XDC, battery knife XK, start contactor QC and starter generator MG; new auxiliary devices include ultra-large capacity capacitor bank C, diode VD, thyristor VT, charge current limiting resistor R and start pump contact QBC. For the Dongfeng diesel locomotive, the battery pack consists of 48 462Ah diesel locomotive batteries. When the battery is fully charged, the voltage is 2.1V, the total voltage is 0, and the internal resistance of the generator is 0.0180. The corresponding large capacity of the auxiliary device. For the capacitor bank, four parallel capacitors with a voltage of 96V and a capacitance of 7F can be used.
In the absence of an auxiliary device, the battery brake knife XK and the start contactor QC are closed at startup, the maximum starting current is 2 100 A, the minimum battery terminal voltage is 38 V, and the start is completed around 7 s.
In the case of using the auxiliary device, according to the step of starting the diesel generator set, after the battery knife KX is closed, the start pump contactor QBC is closed to start the pump to start working; meanwhile, the thyristor VT is triggered to conduct, and the battery pack passes the current limiting resistor R Charge the capacitor bank. The resistance of the resistor can be determined by fully charging the capacitor bank within the preparation time of 12 minutes before the engine is officially started. At the time of official start, the start contactor QC is closed, and the battery pack and the capacitor bank simultaneously output the stored electric energy, and the current through the starter generator is the sum of the battery pack output current and the capacitor output current. The instantaneous maximum current is about 3000A, and the minimum battery voltage is about 55V. Correspondingly, the instantaneous maximum output current of the battery pack is 1500A, and the maximum output current of the capacitor bank is 11.5s. The electric discharge assists. The device acts on the start of the start of the diesel generator set. Compared with the case where no auxiliary device is used, the maximum input current of the starter generator is increased by about 43% and the minimum value of the battery terminal voltage is increased by about 45%, and the instantaneous turn is started when the maximum output current of the battery pack is reduced by 28%. The moment is increased by about 100%, and the starting time is shortened by 1.01.5s. The ultra-large capacity capacitor is used as the line principle of the electric vehicle auxiliary starting device; the MG starts the generator; the C super large capacity capacitor group; the VD diode; the VT thyristor; Flow resistance; when the QBC starts the pump contactor capacitor auxiliary starting device and the fully charged battery pack is started, the ratio of the output current of the battery pack to the output current of the capacitor bank is about 1:1; but when the battery is over-discharged, its capacity When reduced, the output current of the capacitor bank can reach 1.52 times the output current of the battery pack.
Therefore, the worse the state of the battery technology, the more the function of the capacitor group auxiliary starting device can be realized.
3Electric start test of diesel locomotive In order to test the actual performance of super large capacity capacitor as the starting aid of diesel locomotive, and compare with the independent starting performance of battery, Beijing Railway Bureau Beijing Internal Combustion Engine Section and Shijiazhuang Locomotive Depot are respectively on DF12 diesel locomotive (with DF4) The locomotive is loaded with the same power diesel engine and the DF4 diesel locomotive is tested with a super-capacitor capacitor-assisted electric start.
The test on the DF12 diesel locomotive uses a set of four parallel capacitors with a voltage of 96V and a capacitance of 7F. The original car battery is NG462Ah (80% residual capacity), and a NG300Ah battery (80% residual capacity) used in a group of Dongfanghong 5 type locomotive locomotives is also prepared. The test instrument is a 546008 type memory oscilloscope and a 2000 octave.
The test on the DF4 diesel locomotive uses a set of three capacitors with a voltage of 96V and a capacitance of 8.5F. The original car battery was NG420Ah (80% residual capacity), and a group of NG300Ah batteries (80% residual capacity) were also prepared. The test instrument is one HP54602A four-channel 150MHz digital storage oscilloscope and four 1000A shunts.
In the following three cases, the two models were tested for starting the diesel engine: the ultra-large capacity capacitor was connected, and the 462Ah of the original car was replaced with 300Ah, which was supplemented by a large-capacity capacitor.
In these three cases, test data such as current maximum and voltage minimum are shown in Tables 1 and 2.
Table 1 DF12 diesel locomotive starting diesel engine test data starting device voltage minimum value / V battery output current maximum / A capacitor output current maximum / A starting generator maximum input current / A starting time Note separately using battery capacitor auxiliary 462Ah battery 7 start-up tests were successful. Capacitor-assisted 300Ah battery 3 start-up tests were successful. Table 2 DF4 diesel locomotive starts diesel engine test data starting device voltage minimum value / V battery output current maximum / A capacitor output current maximum / A start The maximum input current of the generator/A start-up time note alone battery 3 times start test is successful. Capacitor-assisted 420Ah battery 3 times start test is successful. Capacitor-assisted 300Ah battery 4 times start test are successful. DFi2 diesel locomotive starts diesel test The current curve is as shown. It can be seen from the test data that the 462Ah battery is activated by the ultra-large capacity capacitor, the minimum value of the battery terminal voltage is increased by 60% and 80% compared with the battery start alone, and the battery output current is reduced by 30% and 50%, which is advantageous for the battery; At the same time, the instantaneous torque increase is initiated, which will help shorten the start-up time and improve the startup reliability.
When the container is started, the maximum output current of the battery is only 670A, which is lower than the maximum discharge current (35) allowed by the startup type lead-acid battery. Standard. However, the multiple start-up tests with the aid of ultra-large capacity capacitors have been successful, indicating that the Dongfeng diesel locomotive uses an ultra-large capacity capacitor as an electric start assist device, which can reduce the capacity of the existing battery or prolong its use time.
Dynamic current graph, the lowest voltage is 30V, the current maximum is 2100A. (b) is the current curve of the auxiliary 462Ah battery starting with the large capacity capacitor, the lowest voltage is 49V, the maximum output current of the capacitor For 2240A, the maximum output current of the battery is only 1060A. (c) The current curve of the battery is replaced by 300Ah and the super-capacitor capacitor. The startup is successful twice, the lowest voltage is 40V, and the maximum output current of the battery is 670A. Economic Benefit Analysis Ultra-large capacity capacitors are used as auxiliary devices for electric start of diesel locomotives, and are most suitable for use in frequently-started shunting locomotives. In the past, in order to prevent the battery from losing power, it is required to stop the machine during short standby. After the start-up aid is installed, it can be stopped at any time during standby without any restrictions. This reduces the mechanical wear of the diesel engine and saves fuel.
After installing the electric start assist device, when the diesel engine is started, since 30% of the starting current is more than 50% of the starting current from the ultra-large capacity capacitor, the burden of the battery is much smaller than in the past, so the service life of the battery can be greatly extended, and Reduce the capacity of existing diesel locomotive batteries, reducing cost and weight.
After the installation of the electric starting aid, the reliability of the starting of the diesel engine is greatly improved, especially when the temperature is low and the battery pack is deficient or the electrical parameters are deteriorated.
Due to the increase of the starting instantaneous torque, the rotational acceleration of the diesel engine is increased, the ignition quality of the fuel is improved, and the starting time of the diesel generator set is shortened.
5 Operation and maintenance Since the capacitor is an energy storage device, the first priority in the daily operation and maintenance of the locomotive is personal safety. Therefore, the safety discharge circuit should be considered in the circuit design of the auxiliary device. The discharge circuit can utilize existing equipment on the locomotive (such as a resistor braking circuit, a headlight circuit, or an electric furnace circuit), or can use a charging current limiting resistor in the electric starting aid as a load. The discharge control method can be manual or automatic, and it is safer and more reliable.
6 Conclusion As a auxiliary device for electric start of diesel locomotive, ultra-large capacity capacitor can shorten the starting time, improve the starting reliability and prolong the service life of the battery. Applying such an auxiliary device to an existing diesel locomotive can reduce the capacity of the existing battery, is technically feasible, and can bring significant economic benefits. It is recommended to gradually promote the use of such electric starting auxiliary devices on domestic diesel locomotives.
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