1. Heat dissipation design
In high-current DC applications, the DC standard energy meters calibration bench will generate a lot of heat, so efficient heat dissipation design is essential. The high-power circuit components inside the DC standard energy meters calibration bench, such as power amplifiers, current transformers, etc., will rise sharply in temperature under long-term high-current operation. In order to ensure the normal operation and stable performance of the components, a combination of forced air cooling and heat sinks is usually adopted. The heat sink is made of metal materials with high thermal conductivity, such as aluminum or copper, to increase the contact area with the air and quickly conduct the heat away. At the same time, it is equipped with a powerful fan to form a stable air flow channel to bring the heat out of the DC standard energy meters calibration bench in time. For example, for some DC standard energy meters calibration benches with a rated current of up to thousands of amperes, multiple sets of heat dissipation ducts are specially designed to dissipate heat for key heat-generating components, effectively reducing the operating temperature of the components, preventing the increase of measurement errors or even component damage caused by overheating, and ensuring the continuous and stable operation of the DC standard energy meters calibration bench under high-current conditions.
2. Current sampling and shunt design
Accurate measurement and sampling of large currents is one of the core tasks of the DC standard energy meters calibration bench. Due to the huge current value, direct measurement will cause great impact on the measurement circuit and it is difficult to achieve high accuracy. Therefore, it is a common countermeasure to use a high-precision shunt for current sampling. The shunt converts the large current into a measurable small current signal according to the fixed proportional relationship between the large current and the small current, and then measures it through a high-precision current sensor. The resistance value of the shunt is precisely calibrated and temperature compensated to ensure good linearity and stability in the large current range. For example, in the calibration of electric energy meters in some high-voltage direct current transmission systems, shunts made of special alloys are used, which can withstand DC currents of up to tens of kiloamperes and accurately convert them into small current signals of milliamperes, providing a reliable current data basis for subsequent electric energy measurement and calibration.
3. Insulation and safety protection design
In the high-current DC environment, the DC standard energy meters calibration bench faces severe insulation and safety challenges. High voltage and high current may cause dangerous situations such as arcs and leakage, endangering the safety of operators and affecting the accuracy of calibration. The DC standard energy meters calibration bench adopts a multi-layer insulation structure in design to strictly isolate the high-voltage part from the low-voltage part, and the live part from the shell. For example, high-insulation insulating materials are used to make partitions and sleeves to ensure that there is sufficient insulation distance between components with different potentials. At the same time, it is equipped with a complete grounding system and leakage protection device. Once leakage or insulation fault is detected, the power supply can be quickly cut off to ensure the safety of personnel and equipment. In addition, the shell of the DC standard energy meters calibration bench is made of sturdy and insulating materials with a good protection level to prevent foreign objects or moisture from entering the internal circuit, further improving the safety and reliability in high-current DC application scenarios.
4. Electromagnetic compatibility design
High-current DC systems are often accompanied by strong electromagnetic interference, which will have a negative impact on the measurement accuracy and stability of the DC standard energy meters calibration bench. In order to cope with electromagnetic interference, the DC standard energy meters calibration bench has taken a series of electromagnetic compatibility measures in circuit design and layout. First, shield the sensitive circuits, and use metal shielding covers to wrap the parts that are susceptible to interference, such as signal acquisition circuits and control circuits, to prevent the intrusion of external electromagnetic signals. Secondly, add a filtering circuit to the circuit to filter out high-frequency noise and interference signals on the power line to ensure the purity of the power supply. At the same time, the circuit layout is planned reasonably, and the strong current part and the weak current part are arranged separately to reduce electromagnetic coupling. For example, in the design of DC standard energy meters calibration bench in some large industrial DC power consumption places, by optimizing the electromagnetic compatibility design, the DC standard energy meters calibration bench can still accurately calibrate the DC standard energy meter even when there are a large number of high-power electrical equipment around it that generate strong electromagnetic interference, and the measurement error is controlled within a very small range, meeting the requirements of high-precision energy measurement and calibration.
