Rotary Electric Machine Control Apparatus Short-Circuit Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing control apparatuses for rotary electric machines face difficulties in identifying short-circuit abnormalities in switching elements, particularly at high rotating speeds, due to current exceeding detectable ranges and asymmetrical current deviations, making it challenging to determine the affected switching element.
Innovation Solution
A control apparatus with a DC-AC converting circuit, including serially connected high-potential and low-potential switching elements, and a connecting/disconnecting circuit, uses current detecting means and determining means to identify short-circuits by analyzing changes in current deviations and absolute values, and performs failsafe operations by turning off all switching elements and selectively turning on others to maintain distinct terminal potentials, thereby identifying the short-circuit location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all switching elements are turned OFF to identify short-circuit abnormalities, then the current deviation from zero point can be detected, but the current amplitude increases with rotating speed and exceeds the detectable range of the current sensor
Solution Approach 1:
The connecting/disconnecting circuit is activated preliminarily when a short-circuit abnormality is detected. This circuit electrically connects the rotary electric machine to the DC power supply, establishing a controlled current path before identification proceeds. By pre-establishing this connection, the system ensures that current remains within detectable ranges while enabling accurate identification of the faulty switching element through zero-point deviation analysis.
2Measurement precision
If the current sensor detects current at the upper or lower limit, then the detection range is充分利用, but the identification of the short-circuit abnormality becomes extremely difficult
Solution Approach 1:
The system exploits the asymmetrical current deviation pattern that occurs when switching elements fail. When a switching element short-circuits, the current distribution becomes asymmetrical relative to the zero point, with specific phases showing characteristic deviation patterns. By analyzing these asymmetrical deviations through the connecting/disconnecting circuit operations, the system can uniquely identify which switching element is faulty, even when operating at current detection limits.
3Reliability
If the connecting/disconnecting circuit is used to electrically connect the DC-AC converting circuit and power supply, then current can be controlled within detectable range, but the system complexity increases
Solution Approach 1:
The connecting/disconnecting circuit serves multiple functions: it electrically connects the DC-AC converting circuit to the DC power supply, controls current within detectable ranges, enables short-circuit identification through controlled operations, and provides a safe operating mode during abnormal conditions. By designing this circuit with multi-functionality, the patent avoids adding separate dedicated circuits for each function, thereby limiting the increase in overall system complexity while achieving reliable current control and accurate fault identification.
Data Source
AI summary
In a control apparatus for a rotary electric machine receiving power from a DC power supply, a DC-AC converting circuit is provided with serially connected circuits each having high-potential-side and low-potential-side switching elements. When a short-circuit occurs at the switching elements, all the switching elements are turned OFF for failsafe and a path connecting the machine and the battery is opened. In such a case, a switching element belonging to part of the switching elements is turned ON, with potential at all the terminals of the rotary electric machine being the same. A location of the short-circuit occurs is identified, based on changes in current passing through the machine and being detected in response to turning ON the switching element. The changes are at least one of a reduction change in deviation of the current from a zero point and a reduction change in an absolute value of the current.