In modern industrial and energy systems, monitoring electrical parameters is critical for safe and efficient operation. High-voltage DC (HVDC) power distribution systems, typically used in renewable energy generation, electric vehicles (EVs), data centers, and various industrial applications, require accurate and reliable methods to measure current. One of the most effective methods for this purpose is using an isolated shunt amplifier. This application note delves into the key benefits, functionalities, and applications of isolated shunt amplifiers in high-voltage DC bus systems, particularly focusing on their role in accurate current measurement while ensuring safety, isolation, and signal integrity.
Isolated Shunt Amplifiers
An isolated shunt amplifier measures the voltage across a precision high current resistor (shunt) placed in series with a load or distribution, with this voltage being directly proportional to the current flowing through the system. The isolation feature electrically separates the high-voltage DC bus from low-voltage measurement and control systems, ensuring the protection of sensitive equipment and personnel from dangerous voltages. Shunt-based systems are highly accurate, direct, and non-intrusive, making them ideal for high-voltage DC applications. They provide high-resolution current data without circuit interference. Shunt resistors are often preferred over Hall-effect sensors because they offer superior accuracy, linearity, and stability, especially in environments with potential electromagnetic interference (EMI/EMC). While Hall-effect sensors allow for non-contact measurement, they suffer from temperature drift and lower precision. Shunts, by contrast, offer reliable, stable measurements and are more cost-effective and easier to integrate, making them the optimal choice for precision applications such as energy management, electric vehicles, and industrial power systems.
Shunt resistor selection
Selecting the right shunt resistor is crucial for accurate current measurement in high-voltage DC systems. Key considerations include the resistance value, power rating, and temperature coefficient. The resistance must be low enough to minimize energy losses while generating a measurable voltage drop, effectively converting current into voltage. The shunt resistance should be chosen to utilize the full ±50 mV range over the expected current, maximizing measurement accuracy. The power rating must handle the heat generated by the current to prevent overheating. Additionally, a low temperature coefficient is essential to ensure stable performance, as resistance can change with temperature variations, impacting accuracy.
Safety Considerations
When working with high-voltage DC systems, safety is critical. Isolated shunt amplifiers offer essential protection by electrically separating measurement systems from hazardous high-voltage potentials. However, proper installation and safety protocols—such as using appropriate insulation, protective barriers, and regular system maintenance—remain vital to ensure full safety. At Pinier, we prioritize multiple isolation barriers to protect sensitive equipment from damage and to prevent personal injury. The Pinier Ampera is designed with dual isolation barriers and a potted construction, ensuring robust insulation and providing an added layer of safety in high-voltage environments.Flexible solution
Compared to other shunt-based integrated current sensing solutions, the Pinier Ampera offers significantly greater versatility. This is primarily due to its design, which requires an external shunt resistor rather than an integrated one. By using an external shunt, the same isolation device can be reused across various projects without the need to change part numbers, components, or interfacing requirements. This allows engineers to standardize their designs and simplify inventory management, as the isolation and amplification circuitry remain consistent across multiple applications.
The key advantage of this approach is the design flexibility it provides. Since shunt resistors are available in a wide range of values and sizes, only the shunt needs to be adjusted to suit the specific current measurement range or system requirements. This flexibility allows for easy customization to handle different current ratings and power dissipation needs, without the need for redesigning the entire sensing system. Furthermore, the ability to select the optimal shunt resistor for each project ensures precise and tailored current sensing performance, regardless of the application's unique characteristics. In summary, the Pinier Ampera external shunt configuration provides a versatile, flexible, and scalable solution for high-voltage current sensing, adaptable to a broad spectrum of industries and applications.