Partial Rogowski Coil for Power Module Short-Circuit Sensing
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Solution Overview
Problem
Existing methods for detecting short-circuit currents in power electronics modules are complex, require large spaces for high-voltage sensing, and may not accurately estimate collector currents during normal operation, while Rogowski coils are not suitable for industrial applications due to clearance and creepage distance issues.
Innovation Solution
A power module with a pick-up coil comprising conductor loops wound in a helix, partially surrounding one DC terminal, allowing for the detection of short-circuit and commutation currents without the need for bulky components, and capable of sensing current transients through the DC and AC terminals with minimal space requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Rogowski coil is used to sense current, then current detection capability is improved, but clearance and creepage distance requirements are violated
Solution Approach 1:
The Rogowski coil is divided into two separate winding sections placed at opposite sides of the DC terminal. Each section independently contributes to the sensing capability while maintaining safe distances from the terminal, thus segmenting the harmful electromagnetic coupling into manageable parts that comply with clearance requirements.
Solution Approach 2:
The two winding sections are positioned asymmetrically at opposite sides of the DC terminal rather than symmetrically surrounding it. This asymmetric placement allows the coil to detect current through differential sensing while maintaining the required creepage and clearance distances from the high-voltage terminal.
2Measurement precision
If de-saturation detection is used to detect overcurrent events, then short-circuit detection capability is improved, but device complexity and space requirements increase
Solution Approach 1:
The patent replaces the complex high-voltage sensing system (de-saturation detection requiring isolation distances and blanking times) with an electromagnetic sensing approach using a Rogowski coil. This substitution eliminates the need for high-voltage isolation circuits and complex timing control, simplifying the overall detection system while maintaining short-circuit detection capability.
3Object-affected harmful factors
If measurement distance between DC terminals is increased to account for clearance and creepage, then safety distance is improved, but stray inductance increases
Solution Approach 1:
The Rogowski coil acts as an intermediary sensing element that indirectly measures the current without requiring direct contact or close proximity to the DC terminal. The coil picks up the magnetic field generated by the terminal current at a safe distance, thus maintaining both the required clearance/creepage distances and minimizing stray inductance effects on the power circuit.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables fast and accurate detection of short-circuit events with reduced complexity and space requirements, allowing for reliable operation without the need for high-voltage sensing circuits and expensive current transducers, while maintaining accurate current estimation during normal operation.
Implementation Method 1
a pick-up coil arranged for sensing a time-varying magnetic field generated by a time-varying current flowing through the DC terminals and the AC terminal
Data Source
Figure 1A~1C
Figure 2
Figure 3~4
AI summary
A power module (10) comprises two semiconductor elements (12) connected in series; two DC terminals (20, 22), each DC terminal (20, 22) providing an electrical connection to an outer end of the series connection of the two semiconductor elements (12); an AC terminal (24) providing an electrical connection to a midpoint of the series connection; and a pick-up coil (28) arranged for sensing a time-varying magnetic field (46) generated by a time-varying current (26) flowing through the DC terminals (20, 22) and the AC terminal (24), the pick-up coil (28) comprising a plurality of conductor loops (42) wound around at least one extension section (38, 40) of the pick-up coil (28); wherein the at least one extension section (38, 40) is arranged running besides one of the DC terminals (22), such that the pick-up coil (28) surrounds the DC terminal (22) only partially.