Power electronics process and control the flow of electrical energy.
Factors that affect power electronics reliability are temperature, over current, over voltage, overload, and other environmental conditions.
Component reliability is the cause of most failures in power electronic systems.
These days, it is rare to find an electrical energy system not using power electronics. Around 70% of the electricity that reaches us is processed with power electronics.
Power electronics employ switching circuits to process and control the flow of electrical energy and are responsible for supplying voltages and currents to the load in their most appropriate form. Examples of these circuits include inverters, choppers, and cycloconverters. The classification of power electronics circuits depends on their type of input and output.
Commercial power electronics converters are evaluated on their high power density, high efficiency, low cost, and compact size. However, in the process of achieving these attributes, maintaining reliability in these electronics can become a challenge.
Let’s take a look at recent advancements in power electronics and explore the factors that threaten power electronics reliability.
Advancements in Power Electronics
The last few decades marked the tremendous growth of power electronics. Switching power electronic circuits have made great advances in power systems, power quality, high voltage DC transmission, and portable electronics. Revolutionary advances in semiconductor fabrication technology, semiconductor materials, microelectronics, packaging, and innovations in converter topologies have helped to broaden how power electronics are used.
The increase in use of power electronics makes their reliability that much more important. In the next section, we will explore what threatens power electronics reliability.
Factors Affecting Power Electronics Reliability
Key factors that affect the reliability of power electronics include:
- Over current
- Over voltage
- Environmental conditions
Enhanced designs of converter topologies to satisfy high-power and high-efficient systems usually cause high junction temperatures in switching devices. By having an understanding of the correlation between electrical and thermal characteristics of the semiconductor devices present in a power electronic circuit, designers can try to mitigate reliability issues.
Most power electronic systems operate with pulsed currents. A consideration of the continuous rating of a semiconductor component is not viable for building a reliable power electronics system. The careful designing of power electronic systems is crucial in maintaining the reliability of a system. Parameters to look for when selecting a component include:
- Semiconductor technology
- Device rating
- Power dissipation
- Allowable maximum temperature of operation
Component Reliability and Junction Temperature
Component reliability is a significant cause of many of the failures or faults in power electronic systems. Improving component reliability is an indirect way of increasing power electronics reliability. While choosing a semiconductor switch, such as a MOSFET or IGBT, the resistance of the component in the on-state and the power dissipation are the two most important factors.
At the desired operating temperature, find the on-state resistance of the switch and the power dissipation from the normalized on-state resistance versus temperature graph as well as the power dissipation versus temperature graph. Using the basic power equation, calculate the rated switch current at this temperature. When the semiconductor switch is carrying more current than the rated value at the specified temperature, junction temperature rises, damaging the device. Therefore, temperature should be considered an important factor in component selection.
Power electronics reliability can be threatened by a variety of circuit conditions. The violation of junction temperature in these conditions results in the burning up of power electronic devices. Luckily, Cadence software offers tools that help in analyzing the thermal status of solid-state electronics circuits.