Inverter Fault Detection Using Single Current Sensor
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Solution Overview
Problem
Conventional fault detection devices for inverter circuits require multiple current measuring units, leading to increased complexity and manufacturing costs, particularly due to the need for expensive amplification circuits when using shunt resistors to measure small voltage drops.
Innovation Solution
A fault detection device that applies a first test voltage to the current measuring unit and a second test voltage to the inverter circuit and motor at startup, using a single current measuring unit and amplification circuit, to determine the presence of faults before system operation, simplifying the circuit and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple current measuring units are provided to detect faults in current measuring units, then fault detection capability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies a predetermined test voltage to the current measuring unit before the inverter circuit starts operating. This preliminary test detects faults in the current measuring unit proactively, eliminating the need for multiple redundant measuring units. The test voltage is applied through a switching circuit that isolates the test function from normal operation, simplifying the overall circuit architecture while maintaining reliable fault detection capability.
2Reliability
If multiple current measuring units are provided to detect faults, then fault detection capability is improved, but manufacturing cost increases
Solution Approach 1:
The current measuring unit serves dual functions: it measures current during normal inverter operation and undergoes fault detection when test voltage is applied. This multi-functionality eliminates the need for separate test equipment or multiple measuring units, reducing component count and manufacturing cost while maintaining comprehensive fault detection capability.
Solution Approach 2:
By performing fault detection before normal operation through preliminary application of test voltage, the system identifies defective current measuring units early in the manufacturing or commissioning phase. This prevents costly field failures and reduces the need for expensive redundant components, lowering overall manufacturing cost while ensuring reliability.
3Measurement precision
If shunt resistors are used to measure small voltage drops, then current measurement accuracy is improved, but manufacturing cost increases due to expensive amplification circuits
Solution Approach 1:
The patent changes the voltage parameter by applying a predetermined test voltage that is specifically designed to produce a measurable voltage drop across the shunt resistor without requiring high-precision amplification. The test voltage magnitude is optimized to generate sufficient signal level for accurate fault detection using standard amplification circuits, thereby reducing manufacturing cost while maintaining measurement precision.
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 reliable detection of faults in the current measuring unit, inverter circuit, and motor coils with reduced component count and manufacturing costs, while maintaining accuracy through predetermined voltage ranges and timing.
Implementation Method 1
a test voltage applying unit that applies a predetermined first test voltage to a current measuring unit that measures current flowing in an inverter circuit, and determines whether the current measuring unit has failed or not based on the applied first test voltage
Implementation Method 2
a control unit that applies a predetermined second test voltage to the inverter circuit and the motor, and determines whether the inverter circuit and a coil of the motor have failed or not based on the applied second test voltage
Data Source
AI summary
To provide a fault detection device for an inverter system, that detects a fault in the inverter system including an inverter circuit 2 that converts DC power into AC power and a motor 5 driven thereby. When a driving start signal Sig1 of the inverter circuit 2 is input, a test voltage applying unit 20 applies a predetermined first test voltage to a current measuring unit 10 that measures current flowing in the inverter circuit 2, and it is determined whether the current measuring unit 10 has failed, based on the first test voltage. A control unit 30 applies a predetermined second test voltage to the inverter circuit 2 and the motor 5, and it is determined whether the inverter circuit 2 and a motor coil have failed, based on the second test voltage.