tailieunhanh - Electric Vehicles The Benefits and Barriers Part 8

Tham khảo tài liệu 'electric vehicles the benefits and barriers part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Supercapacitors as a Power Source in Electrical Vehicles 129 - Mechanical transmission between motor and load that adjusts motor speed and torque to torque of the working mechanism load - Data from all elements source converter motor transmission load are collected by regulator controller which based on given required parameters performs automatic drive control. DC source voltage is performed by means of DC-DC converter chopper combined with non regulated rectifier. Figure 6 shows principal scheme of such a system. Fig. 6. Principal scheme of chopper supply To provide breaking or to dissipate braking energy that cannot be returned to the network through diode rectifier it is required to have braking device with transistor T and resistor R. Rectified voltage from rectifier Di - D6 is filtered by simple LC filter and brought to the chopper input that regulates mean value of output voltage Ud. For motor supply there are mostly used chopper voltage reducers so they will be considered here. Figure 7 shows simplified presentation of the chopper supply of a DC motor. Chopper is shown as ideal breaker controlled by voltage Uup so it can control switching on Ton and switch-off Toff exiting voltage Udo . Chopper Fig. 7. Simplified presentation of the chopper supply of a DC motor Chopping frequency is by the definition f 1 1 Ton Toff T 130 Electric Vehicles - The Benefits and Barriers Also compliance factor is defined T d f So output voltage is Ud d Udo So by changing Ton Toff ratio the output voltage Ud can be adjusted between 0 and Udo. Simplified chopper shown can provide only first quadrant operation. For all four quadrant operation transistor bridge as shown in figure 8 can be used L 0 D1 0 D3 Ud0 La ud C A Ra - B 0 3 D D2 Fig. 8. Transistor bridge Fig. 9. Circuit for speed regulation of DC motor with independent field Supercapacitors as a Power Source in Electrical Vehicles 131 By switching on transistor pairs T1-T2 or T3-T4 positive or negative polarity of motor .