Polyphase Machine Fault Detection via Phase Voltage Measurement
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Solution Overview
Problem
Existing power conversion devices fail to detect open-circuit, short-circuit, power, and earth faults in polyphase dynamo-electric machines without causing large currents to flow, making it impossible to diagnose faults accurately.
Innovation Solution
A power conversion device with phase bridge circuits connected in parallel, using power semiconductor switching elements, a DC power supply, and fault determination units that detect phase voltages to identify power, earth, and open faults without inducing large currents, by utilizing discharge and sink type constant current circuits, pull-down and pull-up resistors, and phase voltage detection units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fault detection methods are used to detect open-circuit and short-circuit faults, then fault detection capability is improved, but large currents flow causing false determinations and secondary faults
Solution Approach 1:
The invention changes the detection parameter from current-based to voltage-based measurement. By applying a predetermined voltage to the armature winding and measuring the resulting current only during normal operation, the system can detect faults without causing harmful large currents. The voltage application is controlled through switching elements, and the detection circuit measures voltage drops across current detection resistors only when current actually flows, preventing false determinations during fault conditions.
Solution Approach 2:
The invention introduces an intermediary detection circuit that includes current detection resistors and voltage measurement units. This intermediary system allows indirect measurement of fault conditions by measuring voltage drops across the resistors rather than directly measuring large currents. The switching elements act as intermediaries to control voltage application and isolation, enabling safe fault detection without direct exposure to potentially harmful currents.
2Measurement precision
If voltage is applied to detect faults in armature winding, then detection precision is improved, but current may flow causing harmful effects
Solution Approach 1:
The invention applies partial action by using a predetermined voltage that is sufficient for detection purposes but controlled in magnitude and duration. The voltage is applied only when switching elements are in specific states (both ON or both OFF), and the detection circuit only measures when current actually flows through the current detection resistors. This partial application of voltage achieves adequate detection precision without inducing harmful excessive currents that could cause secondary faults.
3Device complexity
If simple detection circuit is used, then device complexity is reduced, but inability to detect all fault types (open-circuit, short-circuit, power, earth faults)
Solution Approach 1:
The invention achieves multi-functionality by using a single detection circuit architecture that can detect all four fault types (open-circuit, short-circuit, power, and earth faults) through different switching states and measurement configurations. The same current detection resistors and voltage measurement units are used universally across all detection scenarios by controlling the switching elements in different states, eliminating the need for separate detection circuits for each fault type while maintaining comprehensive detection capability.
Data Source
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AI summary
Provided is a power conversion device, including a fault determination unit (11) for determining, based on phase voltages of a polyphase dynamo-electric machine (4) detected by phase voltage detection units (10), a power, earth, or open fault of armature windings of the polyphase dynamo-electric machine (4). The fault determination unit (11) determines, in a state that all power semiconductor switching elements (2) are in an off state and no induction voltage is generated in the armature windings of the polyphase dynamo-electric machine (4), the power fault when all the phase voltages are substantially equal to an anode potential of a DC power supply (3), the earth fault when all the phase voltages are substantially equal to a cathode potential of the DC power supply (3), and the open fault when all the phase voltages are not substantially the same potential.