PDU Input Current Measurement Without CT Sensors
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Solution Overview
Problem
Traditional power distribution units (PDUs) in data centers require current transformers (CTs) for input current measurement, which adds cost and space constraints due to the need for extra shielding and calibration.
Innovation Solution
A PDU system that determines input RMS current without a CT at the input, by sampling instantaneous currents from multiple outputs at identical intervals over a full line cycle, storing aggregated measurements, and generating a composite waveform to calculate the RMS value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Current Transformer (CT) is used to measure input current, then measurement accuracy is improved, but device complexity and cost increase due to additional hardware components and calibration requirements
Solution Approach 1:
The patent extracts the current measurement function from the traditional CT-based hardware approach and relocates it to the software/firmware domain by sampling output currents and computing input current through mathematical aggregation. This removes the need for physical CT sensors at the input while maintaining measurement capability through computational methods.
Solution Approach 2:
The patent creates a virtual representation of the input current waveform by aggregating and summing the instantaneous current measurements from multiple outputs. This composite waveform serves as a computational copy of the actual input current, enabling RMS calculation without direct physical sensing at the input.
2Measurement precision
If a Current Transformer (CT) is installed at the input, then input current measurement is achieved, but space requirements and shielding needs increase
Solution Approach 1:
The patent removes the physical CT sensor from the input path, eliminating the need for additional space dedicated to housing and shielding the transformer. The measurement function is extracted and performed computationally using existing output current sensors, freeing up physical space within the PDU.
3Measurement precision
If traditional CT-based measurement is used, then input current can be measured, but calibration requirements and manufacturing complexity increase
Solution Approach 1:
The system performs self-calibration by leveraging the inherent relationship between input and output currents. By sampling all outputs simultaneously and aggregating their instantaneous current values, the system automatically computes the input current without requiring external calibration procedures or factory adjustments, making the manufacturing process simpler.
Data Source
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AI summary
According to various aspects and embodiments, a power distribution unit (PDU) is provided. The power distribution unit includes an input configured to receive input power, a plurality of outputs each coupled to the input and configured to receive input power, and each output of the plurality of outputs having an output configured to provide output power, and a controller coupled to the plurality of outputs and configured to determine a plurality of time intervals based on a frequency of the input power, measure a current at each time interval of the plurality of time intervals for each output of the plurality of outputs, generate a plurality of current measurement sums based on current measurement values associated with each time interval of the plurality of time intervals, and determine a root-mean-square (RMS) value based on the plurality of current measurement sums.