When it comes to electronic switching in load-control applications, solid-state relays (SSRs) deliver the speed and reliability required. SSRs have no moving parts to affect wear or accuracy, enabling not only predictable operation, but also significantly longer operational lifetime. Where electromechanical relays can switch at most a couple hundred cycles, an SSR can easily achieve 2 million cycles in its lifetime. Shock and vibration resistant, SSRs can operate in harsh environments, immune to magnetic noise, and position insensitive.
There are many power-hungry loads that can easily overheat to the point of damage or destruction if not protected against thermal situations. Most large motor-driven applications require a system to sense overheating and switch the power off. With all the advantages that SSRs provide, there is a thermal management component to their operation, as they consume power whether open or closed, just like the motors that they control. Should overheating occur, finding and replacing an inoperational SSR takes time and money. More than just a maintenance issue, if an SSR’s heat causes the temperature to exceed the product’s tolerance, it can cause issues from negative operational lifetime to short-circuits to catastrophic failure.
Sensata has developed a novel SSR technology that integrates a thermostat into the SSR itself to ensure that the relay always operates in a safe or protected mode. This gamechanging design incorporates all the advantages of standard SSR technology, but is differentiated by its ability to prevent the SSR from overheating, thus protecting component and system operation from potential damage or shut down. Input power is cut when the temperature goes beyond the specified maximum (as determined by the application requirements}. Power is automatically turned on again when the temperature has cooled down to within the normal operating range. The thermostat senses the internal temperature of a mechanical interface with a metal plate, and if the heat exceeds the normal range, it sends a signal to the SSR to turn off the power. This built-in thermal protection completely prevents overheating conditions by providing a trip before equipment damage can occur.
In addition to preventing overheating, the integrated thermal protection function can troubleshoot issues from incorrect heat sinking capacity or poor installation to the heat dissipation efficiency of the system, as well as other issues. For example, consider a conveyor belt application where a motor could stick and cause overload and potential damage to the system. In this case, the SSR with integrated thermal protection would prevent overheating from occurring by shutting down the conveyor belt as soon as a pre-determined heat threshold was met within the SSR’s thermostat. Even non-traditional situations such as hacking and viruses can be addressed, because if a given motor system is running too hot because of unauthorized commands, the thermally-protected SSR would prevent damage to the system.
For more information visit www2.sensata.com/ssrs-thermal-protection