Posted on: July 1, 2014
What is Abnormal Failure?
Abnormal Failure is an artificially induced failure of a component, usually as a result of abnormal testing for regulatory agency safety compliance.
A single or combination of fault conditions may be applied to the electronic equipment such as a power supply unit, with and without the load. The aim of abnormal failure tests are to check the safety of the circuit and its protection circuit operation under the fault conditions and ensure compliance with set safety and environmental standards.
The abnormal failure tests include subjecting the semiconductor components to extreme temperature, excess voltage or current and simulated fault conditions such as short circuits. This checks whether the devices can withstand worst case conditions that may arise in practical applications.
In addition, abnormal fault responses are used by the manufacturers to improve on the design and eliminate dangers that may arise from fires arising from excessive temperatures generated under the fault conditions.
According to IPC-9592, Performance Parameters for Power Conversion Devices regulations, the following is expected;
“Abnormal Testing (Protection, Brownout, Load and Startup Tests) – AC/DC Devices Only. NOTE: Under no conditions shall smoke, burning, the smell of burning or flames be permitted as a result of failures found in any testing.”
Electronic devices are required to comply with the international regulatory standards on safety, environmental impact, and electronic interference.
The components or equipment may be subjected to:
- Low and high temperatures
- Cyclic temperatures
- High humidity
- Ac noise tolerance
- Electrostatic discharge test
- Instantaneous power interruption
- Voltage fluctuation i.e. ±15%
- Frequency fluctuation ±5Hz
- Lightening surge test 8kV
- vibration test
- Short and open circuit tests
- Insulation resistance
- Leak current test
- Current consumption at full load
- In rush current
- Terminal noise voltage
Component Temperature Rise Test
The maximum rated current is applied to the component after which a thermographic camera is used to analyze the thermal distribution as the temperature rises on each component.
Open and short circuit Tests
Deliberate short and open circuits are created on the circuit and a thermographic camera used to check for abnormal thermal emissions. The test is done to ensure that the design conforms to standards and that there is no danger of fire ignition from such faults.
Any abnormal thermal emission and other safety issues should be addressed by the use of a better design and components. All Counter-measures in event of failures should be effective and safe whenever a fault occurs.