Introduction And Selection Of PDU Core Electrical Components--Fuse

Introduction and Selection of PDU Core Electrical Components--Fuse

The new energy vehicle fuse is the last firewall for high voltage protection in the new energy vehicle (the fuse is the last effective protection device when all other protections fail).

Let's first take a look at the high-voltage power distribution box, referred to as PDU (Power Distribution Unit), the high-voltage power distribution unit in the high-voltage system solution of new energy vehicles. The high-voltage components are electrically connected through the busbar and wiring harness to provide charging and discharging control, power-on control of high-voltage components, circuit overload and short-circuit protection, high-voltage sampling, low-voltage control and other functions for the high-voltage system of new energy vehicles to protect and monitor the operation of the high-voltage system. . PDU can also integrate BMS main control, charging module, DC module, PTC control module and other functions. Compared with traditional PDU, there are more vehicle function modules, which are more integrated in function and more complex in structure, with water cooling or air cooling, etc. heat dissipation structure. The PDU configuration is flexible and can be customized and developed according to customer requirements, which can meet the needs of different customers and different models. BDU (Battery Disconnect Unit) battery pack disconnect unit, specially designed for the interior of the battery pack, is also a kind of high voltage distribution box.

Introduction of fuse fusing principle:

Function of fuse: Under normal circumstances, the fuse plays the role of connecting the circuit in the circuit; under abnormal (overload) conditions, the fuse acts as a safety protection element in the circuit, which can safely cut off and protect the circuit through its own fuse. The function of the fuse is to protect the electrical equipment and prevent the electrical equipment from being damaged due to overload.

Three key parameters of fuse

1. Rated voltage;
2. Constant current;
3. Limit breaking: This is the maximum short-circuit current that the fuse can reliably break under fault conditions, and it is one of the main technical indicators of the fuse.

Primary selection of fuses

1. Understand the preliminary needs of customers: such as rated voltage, rated current, peak charge and discharge current, peak current duration, seismic performance, working environment requirements, altitude, life requirements, etc.;

2. The working voltage of the fuse is not less than the rated voltage of the PDU.

3. Continue to narrow the range according to the rated current and peak current, and choose a relay that is larger than the rated current and smaller than the peak current. For example, the rated current of the PUD is 200A, the peak current is 400A, and the rated current of the fuse should be 300A or 350A.

4. Because the fuse is blown by thermal energy, the thermal energy is affected by heat conduction, air cooling, liquid cooling, frequency factor, and environmental factors of the fuse installation housing, so it is difficult to accurately estimate the service life. The rated current of fuses is generally selected according to experience: The rated current of the fuse is 2 times to 2.5 times the rated current of the PDU, but does not exceed the peak current of the PDU.

5. Follow up the fuse blowing time curve table, and correct whether the PDU peak current duration is less than the fuse blowing time. If it is less than the fuse blowing time, the initial selection is correct.

6. In principle, on-line testing is recommended; the high-voltage system is a very complex system, and factors such as the withstand voltage level of other materials, electrical design, overcurrent design of copper bars, assembly process and other factors need to be comprehensively considered.