In order to obtain the reliable comparative results of the three power system performance, key power components must also be designed and selected. 5T ordinary hydraulic excavation machine Power Configuration Diesel engine PEC is 32KW / 2200RPM, 5T hydraulic excavator needs to achieve dynamic performance as Table 2:
Since the performance of the above 5T excavator describes its maximum operating ability, the power parameters of the designed mixed power excavator cannot be used for this to meet the power requirements of the heavy-duty excavation, as the parameter design of the two hybrid systems. . As described in 1.2, the hybrid system is only available to the average power source of load requirements due to its dual-active source structure. The load data of the heavy-duty condition is calculated in the formula (1) to obtain its average power = 16.3 kW.
For the series system, all the energy of the engine output is generator, the energy conversion of the motor, and the efficiency is NMO and NW, respectively.
The energy of the part is X is also required to experience the charge and discharge of the battery pack, the efficiency is AXR. Therefore, the active source selection of the series system needs to satisfy the formula (2):
According to the data provided by the partner unit, 7d = 91% and 7u = 92% 7axr = 72%, and X = 0.22 is taken according to the load fluctuation statistics. You can obtain ES = 21.05 kW. Therefore, the rated power is 22kw / 2200 rpm. Power generation Machine rated power 22 kW / rpm. Because the hydraulic system is finally driven by the motor, the motor power is selected from the normal excavator engine power, and is 32 kW / 2200 rpm.
It should be noted that the above calculation results do not consider the improvement of the engine efficiency, so that the margin coefficient of the engine is ignored.
The combined force system uses the same design calculation method as the series system. Different, and the energy output of the engine output is not all converted to electrical energy, and the control policy can more flexibly control the power output ratio of the dual power source. The energy efficiency of the selected key component is: NAX = 90% when the electric / generator is moderate mode, and the power generation mode is EC = 89% (because the speed is still fluctuated, so the electric / generator efficiency is relatively low. ), Battery pack efficiency is still 65%. The engine output energy experiences the ratio x = 0.2 of the electrical energy conversion (because the operating point of the system engine will fluctuate with the load, the proportion is lower than the series system. Calculating formula, as shown, according to the calculation result Select the rated power of 20kW / 2200rpm. The power generator power is 15kW / 2200rpm.
For the selection of battery packs, it is mainly considered for three aspects: 1) The capacity of the battery pack does not limit the operating performance of the motor; 2) High efficiency charging can be performed when power generation energy storage mode; 3) is capable of satisfying the entire machine Life requirements.
