How to solve the resistance stability in the application of battery precharge and capacitor charging and discharging?

In the circuit of capacitor charging and discharging and battery pack precharging, the following three resistances are commonly used:

Gold aluminum shell resistance、Aluminum shell winding resistance and plane power resistance

The common point of the above three resistances is that the resistance element is either the resistance wire wound on the insulation framework or the resistance paste attached to the insulation matrix. For a long timeloading amountsetWhen the power is working, the winding wires of gold aluminum shell resistance and aluminum shell resistance can be cooled by insulating filler and external aluminum shell, and the plane power resistance can also be cooled by ceramic matrix and external radiator. However, when an instantaneous pulse comes in, there is not enough time for the heat to dissipate, so the heat will gather on the originally small resistance elements. The instantaneous pulse energy is very likely to cause the resistance damage or direct failure.

In addition, both the gold aluminum shell resistance and the aluminum shell wire wound resistance are bulky, which is not conducive to saving space and reducing weight.

So how to consider small volume, high energy, pulse resistance and high reliability? The answer is to use solid non inductive ceramic resistors.

The core ceramic synthetic resistor is not a new resistor technology. It was invented by carborudum company, the predecessor of Kanthal company in 1927. Now, Kanthal belongs to Sandvik Group of Sweden, a group company with annual sales of more than 10 billion US dollars.

The most important difference between the solid ceramic synthetic resistance and the wire wound resistance is that it is conductive, completely insensitive and has a high energy density. Solid ceramic resistors provide designers with a smaller and more compact structure than wire wound resistors. For example, a wire wound resistance with a rated power of 20W and a rated energy of 150j has a length of about 70mm and a diameter of about 10 mm. Under the same electrical parameters, the solid ceramic resistance of an axial pin shall not exceed 20 mm in length and less than 8 mm in diameter.

实The other main feature of the core ceramic resistance is its high reliability. It can'timage winding resistancebroken wire or burning of membrane resistor. This is why solid ceramic resistors have been used in military equipment and aerospace fields. Solid ceramic resistor is used as the precharge resistor of electric vehicle battery, which can ensure that it will not be damaged in the most extreme cases, with high reliability, and the volume is only 20% or less of the wound resistance, and the price is equivalent to the wound resistance. The following table shows typical applications of solid ceramic resistors:

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