Intelligent power distribution units (PDUs) are integral to modern data centers, powering critical equipment for edge AI processing, server hosting, cloud computing, and storage. Unlike standard PDUs, these units feature input/output current monitoring, remote control, and protection against overcurrent and overvoltage events, which can greatly help enhance system efficiency and uptime. As AI power demands continue to rise, these PDUs are now employed to power remote supervision of individual inlets and outlets, delivering precise current readings and streamlined Level 3 power usage effectiveness management.

PDUs must also address sudden surge events, caused by lightning strikes or server usage spikes, that can damage IT units and AI servers. To mitigate these risks, protection strategies need to include overvoltage-protection components such as metal oxide varistors (MOVs) and surge-protection devices (SPDs), current shunt monitors (CSMs), and positive temperature coefficient (PTC) resettable fuses that safeguard sensitive equipment. Robust overvoltage and overcurrent protection with proper current monitoring helps ensure that IT hardware remains efficient and secure.

This article discusses the threats that can degrade efficiency and valuable uptime in intelligent PDUs. In particular, the use of current shunt resistors in CSMs is highlighted as well as the importance of implementing an optimized surge-protection solution that supports energy-efficient computing.

Current measurements using CSMs

A primary feature of intelligent PDUs is the integrated inlet and outlet current monitoring. This capability enables computers to record and analyze each server’s power consumption, thereby improving energy efficiency, reducing costs, and extending system lifespan.

Current sensors in power delivery devices must be cost-effective in construction and yet minimize any power loss. CSMs with a properly chosen current shunt fulfill that role in meeting these requirements.

A CSM measures current by detecting voltage drop across the shunt, a low-value resistor with capabilities to pass high energy. The value of the shunt resistor is always known to a very precise degree. As drawn in Figure 2, using Ohm’s Law (I = V/R), the current can be calculated with the measured voltage and the known resistance. This method provides accurate, real-time measurements of the status of the servers while consuming an insignificant amount of power.

Figure 1: The shunt resistor is an integral component in current measurement. (Source: Bourns Inc.)

PDUs are designed with compact form factors to optimize space in server cabinets. Engineers often employ CSMs with custom shunts to meet tight spatial constraints, enhancing flexibility and measurement accuracy.

Surge protection inside and outside an intelligent PDU

Power surges can be a major risk for data centers. Lightning strikes, power grid fault, HVAC cycle fluctuations, faulty uninterruptible power supplies, server reboots, and AI processing spikes all could potentially damage server devices, leading to costly downtimes.

Intelligent PDUs leverage several types of protection devices to protect server devices from any potential surges. These include SPDs, MOVs, and overcurrent-protection devices such as temperature-sensitive PPTC resettable fuses.

Starting at the service entrance and leading to the PDU are a string of SPDs. These devices will absorb most of the excess surge energy and prevent overvoltage conditions. The list below highlights the importance of properly installed SPDs in critical power delivery infrastructure to counteract overvoltage conditions:

• Primary protection (service entrance): This is the first line of defense against large, externally originating surges, such as those caused by lightning strikes or disturbances in the power grid. These surges typically enter the electrical system through the service entrance, making it crucial to install robust protection at this point to prevent damage to downstream systems and equipment.
• Secondary protection (distribution panels): This provides additional protection by preventing residual surges that may have passed through the primary protection from propagating further into the electrical distribution system.
• Tertiary protection (point of use): This protects sensitive and critical equipment such as servers and networking devices directly at their power inputs, minimizing downtime and damage.

SPDs are widely used as the first line of defense for PDUs. These devices clamp the high-intensity voltages to safe levels, protecting the circuit from large overvoltage and overcurrent events. Without the inclusion of an SPD, a PDU or downstream servers could be destroyed or irreparably damaged. An SPD paired with a traditional fuse or circuit breaker can help ensure a server cabinet is safeguarded from high-voltage lightning strikes or other outside surges.

Figure 2: SPDs are the initial defense against high voltage surges. (Source: Bourns Inc.)

While an SPD absorbs most incoming energy, residual surge power can still pose a threat. To mitigate this, the PDU input and individual outlets can include an MOV or a power TVS (PTVS) diode.

Figure 3 highlights their differences. PTVS diodes provide a more precise level of voltage clamping, while MOVs are typically employed to handle higher-voltage spikes as a stronger surge-protection approach. Both absorb excess energy in the range of hundreds of volts, compared with the thousands absorbed by SPDs. This mid-range voltage protection is essential for the reliability and longevity of processing servers.

Figure 3: Comparison of a PTVS diode and an MOV (Source: Bourns Inc.)

Intelligent PDUs also integrate Ethernet and USB connectivity, necessitating a different approach for protecting this type of delicate circuitry for data communication. To support most communication protocols, input voltages ranging from 100 V to 400 V must be stepped down to a stable 1 V to 5 V. This significant reduction of 1% to 5% of the original voltage requires multiple voltage-stepdown stages, with each needing to be safeguarded by an overvoltage protector to counter potential voltage spikes.

PPTC resettable fuses excel in this role by opening the circuit when excessive current is detected. Unlike traditional fuses that require manual replacement once tripped, PPTC fuses automatically reset after the surge dissipates. This self-resetting capability minimizes downtime and maintenance costs while ensuring continuous protection for sensitive communication equipment. Figure 5 illustrates why PPTC devices offer critical protection in the circuitry of a USB interface.

Figure 4: Simple schematic featuring an MF-NSMF200-2 PTC device (Source: Bourns Inc.)

Maximizing data center efficiency

Intelligent PDUs serve as the essential backbone of modern data centers, enabling efficient energy management and safeguarding critical IT infrastructure. By integrating advanced current monitoring, remote control, and layered surge protection, these PDUs can help deliver the high reliability and uptime essential for demanding edge AI processing, server hosting, cloud computing, and storage applications.

Taking a multilayered surge-protection approach, combined with real-time analytics, aids in maintaining energy efficiency even under fluctuating load conditions. These intelligent systems enhance overall system lifespan, reduce maintenance downtime, and contribute to cost-effective operations.

Furthermore, by supporting Ethernet and USB connectivity, properly designed intelligent PDUs with protection facilitate seamless data communication and network integration. In an era of escalating AI power demands and centralized data processing, these units are indispensable for achieving robust performance and energy-efficient computing. They also provide the essential functions that help minimize operational risks and enable more future-proofed data center architectures with enhanced reliability and longer lifespans.

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