PLCs and VFDs are the backbone of modern control systems in industrial automation, regulating power and speed to bring precision into almost every automated process within production lines. But there is one threat, invisible to them, which slowly erodes their performance: heat.
Overheating is often considered the "silent killer" of automation electronics, because internal component damage is progressive, which can reduce equipment life and plant productivity without an immediate overload. Knowing why heat builds up and how to prevent it can spell the difference between smooth operation and costly downtime.
Why Heat Is the Hidden Enemy
One of the most dangerous and devious dangers in industrial automation is heat. It is subtle, and it is insidious; it does not make a lot of noise as do electrical faults or mechanical failures, it destroys internal components and does it quietly and slowly and quietly destroys internal components before an operator notices that something is wrong. Semiconductors, capacitors, processors, I/O modules, and power circuits, which are very temperature sensitive, are used to construct PLCs and drives. The excess heat accumulated in the control panel or in the device itself puts these components well above their safe operating limits. Even a minor increase in temperature is statistically significant to speed up the aging process, deteriorate insulation, and raise resistance in electronic parts. Thermal stress causes devices to act in an unpredictable fashion-they cause communication errors, derate, false triggers, or they would just fail. In addition to simply making the life of PLCs and drives shorter, heat is a silent killer of reliability and efficiency and increases the potential of costly unplanned downtime. That is what makes heat the indeed the so-called silent killer of automation systems: it strikes slow, invisible, constantly until the damage is so severe that it can no longer be overlooked.
How heat can damage drives and PLCs
Heat is likely the most devastating and least familiar threat to the wellbeing of Drives and PLCs. Electronic components of such devices are very sensitive to the temperature and can only be used within a well specified range of temperature. Once the temperature exceeds this temperature, physical, chemical, and electrical degradation of the system will take place, damage is slow, quiet, and cumulative and eventually leads to performance problems, instability, and complete failure. A more detailed analysis of the effects of heat on each component of drive or PLC is as follows:
1. Accelerated Component Aging
Increment of 10 o C in temperature shortens the life of electronic components by about half. Electrolyte evaporation in capacitors is accelerated by heat making the capacitors dry up and lose their voltage stability capacity. Power semiconductors including MOSFETs and IGBTs have a shorter degradation life, which decreases their efficiency and increases switching losses.
2. Increased Resistance to Electricity
Temperature increase increases the conductance of conductor and PCB traces. As the resistance increases, the power dissipated in a self-heating feedback loop also increases. The device becomes hot and the resistance rises a little further and the process repeats itself until one of the components fails significantly.
3. IGBT and Power Module (Drives) Thermal Stress
VFDs use IGBTs in order to convert and control electrical power. Overheating leads to the silicon in these transistors developing micro-cracks or thermal runaway, leading to:
-
erratic switching
-
overcurrent trips
-
blown power modules
-
Complete drive failure
It is among the most common- and the most expensive- drive failures: IGBT overheating.
4. CPU Degradation and Logic errors (PLCs)
PLCs run on rigid CPU timing to scan logic, read the inputs and do outputs. Heat disturbs this balance, and results in:
- slower scan cycles
- corrupted memory
- frozen processes
- abnormal resets or watchdog timer malfunctions
- wrong control decisions
A PLC can act unpredictably when hot, as it can cause the operation of a whole machine to be unpredictable.
5. Communication Instability
The drives and PLCs are continuously communicating using the EtherNet/IP, Profibus, Modbus, Profinet, CAN, and serial protocols. These signals are distorted by heat to degrade crystal oscillators and transceivers resulting in:
- broken communication channels
- poisoned network connectivity
- Misreads or false alarms by the sensor
This may shut down complete production lines although the device may not have stopped.
6. Fan, Filter and Cooling System Malfunction
The majority of the drives rely on internal cooling fans. Dust and heating lead to relatively short lifespan of the fans. When fans fail:
- internal temperature rises
- the machine has a self-derating mechanism
- thermal trips are common
- critical parts burn out
A single failure of fans will burn a complete drive in a few hours.
7. Thermal Paste, Adhesive and connector failures
Internal parts have a lot of thermal paste, glues and pressure contacts in order to sustain cooling. These materials are dried by heat and leave areas with less heat transfer, which makes them even more heat transfer resistant, leading to even higher overheating and hot spots.
8. Thermal Derating
In order to save themselves, drives automatically reduce their output when warmer. With high ambient heat the drive does not bring full performance and minimizes:
- torque output
- motor speed range
- efficiency
-
Production capacity
Continued derating is an indication of severe thermal stress.
The heat is, probably, the most silent, but the most devastating risk of automation systems, and its consequences on PLCs and VFDs cannot be overestimated. Being the foundation of the modern control and power regulation, these devices are dependent on the stable temperatures to provide highly controlled and dependable performance. Once excess heat is present whether through bad ventilation, the environment, or strain of the internal components, then it initiates a slow yet inexorable process of degradation-by accelerated component life and compromised capacitors to IGBT failures, CPU instability, and communication errors. Over time, the thermal load progressively decreases efficiency, leads to derating, and creates unexpected shutdowns, and greatly reduces equipment life. That is why due thermal management is not only a maintenance issue but also a essential investment into uptime, productivity and operational safety. Industries can save their drives and PLCs the silent threat of heat through temperatures, clean airflow, replacement of worn cooling parts, and panel designs to enhance the dissipation of heat. There is no worse variable in a world to pay in downtime and reliability than, heat control which by far is one of the most efficient methods to ensure your automation systems are operating at their optimum.
