Bridge Circuit Testing in Rotating Machine End Stages
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Solution Overview
Problem
Current methods for testing bridge circuits in output stages, particularly in drive inverters, fail to detect errors and temperature-dependent defects reliably, leading to potential thermal incidents and system deadlocks, especially during startup and restarts, due to inadequate consideration of voltage differences between phases and inability to distinguish between healthy and faulty MOSFETs.
Innovation Solution
A method that uses existing hardware elements to determine machine speed and perform low-speed tests or observations, allowing for the detection of defects in MOSFETs and windings without redesigning hardware, using differential voltage measurements and cyclic drain-source voltage measurements to assess the state of switches and ensure system functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low-speed test is performed to detect insulation faults and malfunctions, then detection sensitivity is improved, but the test cannot be performed when the machine is rotating above a threshold speed
Solution Approach 1:
The patent implements a dynamic testing strategy that adapts the test method based on machine speed. When speed is below the threshold, a low-speed test with high detection sensitivity is performed. When speed exceeds the threshold, the system switches to observing driver states. This dynamic adaptation resolves the contradiction by making the testing method flexible rather than fixed, allowing the system to maintain both high detection sensitivity when conditions permit and operational versatility across all speed ranges.
2Reliability
If drain-source monitoring with a trigger threshold of 2.5 times maximum rated current is used, then thermal incident prevention is improved, but temperature-dependent defects cannot be detected reliably
Solution Approach 1:
The patent applies partial testing action by performing low-speed tests only when the machine is rotating below a certain threshold speed. This partial application of the test allows detection of temperature-dependent defects under controlled conditions where the differential voltage between phases is minimal, while the 2.5x trigger threshold monitoring continues to provide thermal incident prevention during normal operation. The combination achieves both goals without requiring the test to be performed under all conditions.
3Reliability
If permanent monitoring with short circuit detection is implemented, then real-time fault detection is improved, but system deadlocks occur due to undervoltage reset after cross-circuit detection
Solution Approach 1:
The patent implements a feedback mechanism where the microcontroller continuously monitors machine speed and adjusts the testing strategy accordingly. When a cross-circuit is detected during permanent monitoring, the system uses speed information to determine whether to perform a low-speed test or observe driver states, preventing the undervoltage reset deadlock that occurs with conventional permanent monitoring alone. This feedback-based adaptation maintains both real-time fault detection capability and system stability.
4Measurement precision
If a bridge test is performed during start-up to detect early faults, then fault detection capability is improved, but the test fails when differential voltage between phases is present due to machine rotation
Solution Approach 1:
The patent changes the testing parameter based on machine speed. Below a certain speed threshold, the low-speed test is performed with high fault detection capability. Above the threshold, the system switches to observing driver states. This parameter change resolves the contradiction by adapting the test conditions to match the operational state, ensuring the bridge test can be performed when differential voltage is minimal while maintaining test applicability across all operating conditions through the alternative observation method.
Data Source
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AI summary
The invention relates to a method for testing bridges of an end stage, comprising a microcontroller (μC), a first bridge circuit (B10) and a second bridge circuit (B4), in a rotating machine (M), which method comprises the method steps of determining a speed of a machine, which is operated by means of the bridge circuits of the end stage, by the microcontroller (μC), and carrying out a low speed test, if the determined speed does not exceed a predefined threshold value, or carrying out an observation of drivers provided for the bridges, if the determined speed corresponds to or exceeds the predefined threshold value.