Grounding resistance cabinet is the same as other resistors. Grounding resistance cabinet represents the size of conductor's blocking effect on current in physics. The greater the resistance of the conductor, the greater the resistance of the conductor to the current. Different conductors have different resistance. Resistance is a characteristic of conductor itself. The smaller the resistance, the greater the electron flow, and vice versa. The resistance value of components in grounding resistance cabinet is generally related to temperature, material, length and cross-sectional area. The physical quantity to measure the resistance of aluminum shell affected by temperature is temperature coefficient, which is defined as the percentage of resistance value change when the temperature increases by 1 ℃.
1、 It is selected according to the resistance value and error of resistor
2、 Resistance selection: the principle is that the smaller the difference between the nominal resistance value of the resistor used and the resistance value of the required resistor, the better.
3、 Error selection: the error of resistor required for time constant RC circuit should be as small as possible. Generally, it can be selected within 5%. For decoupling circuit, feedback circuit, filter circuit, load circuit, the error requirement is not too high. 10% - 20% resistor can be selected. According to the limiting parameters of resistor
4、 Rated voltage: when the actual voltage exceeds the rated voltage, the resistor will be damaged even if the power requirement is met.
5、 Rated power: the rated power of the selected resistor should be more than twice of the actual power to ensure the long-term reliability of the resistor in the circuit. As we know, the grounding resistance cabinet used in the industry is generally used to make braking, so it is also called braking resistance. For systems with large inertia, when the grounding resistance cabinet slows down, the motor generates electricity, and the DC voltage of the grounding resistance cabinet increases. When the voltage rises to a certain value, the braking resistor will be used to release the energy generated by the motor in the form of heat. Especially in frequent braking, a lot of energy will be consumed, and the capacity of the braking resistance will be increased.