As SSRs generate heat when conducting current, there is
a thermal management component to their operation, just
like the motors they control.
Should overheating occur, diagnosing and replacing a
damaged SSR can take time while the assembly line or
manufacturing system is down and out of service, cutting
into operations and running up expenses.
When the SSR turns on to generate current, it also
generates heat. Failure to adequately protect the SSR can
cause damage to the relay or to the load.
So How Do You Protect the SSR Itself From Overheating?
To address this overheating challenge, Sensata has
developed a new SSR technology that integrates a
thermostat into the SSR itself to ensure that the relay
always operates in a safe or protected mode. This new
design is differentiated by its ability to prevent
the SSR from overheating, thus protecting
component and system operation from potential
damage or shut down.
The new SSR cuts off input circuit power
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 cool and
restart phase usually takes only a few minutes.
This automatic thermal protection is
accomplished by using an integrated thermostat
embedded in the SSR. The thermostat senses the
internal temperature of a mechanical interface with
a metal plate where the internal power-switching
device is mounted. 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, thereby
saving time and money.
In addition to preventing overheating, this
integrated thermal protection function can help
troubleshoot design issues in the system. It can help
identify incorrect heat sinking capacity in the SSR
or system, poor installation resulting in insufficient
heat sinking contact, heat dissipation efficiency of
the system, and other issues.
While developed for use in a commercial
refrigeration application, this SSR design can be
adapted to other industrial and manufacturing
applications. For example, consider a conveyor
belt application where a motor could stick, causing
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 once a pre-determined
heat threshold was met within the SSR’s thermostat.
In injection molding applications, where limited space
can cause the temperature in the cabinet to rise, thermal
protection prevents the SSR from overheating if the
heatsinking is not adequate, thus avoiding costly repairs.
For heating systems, the thermally protected SSR can
help shut down the heating element if there is a problem
with the temperature controller that causes a temperature
runaway, thereby protecting the entire system.
SSRs provide robust solutions for electronic switching
in load control applications and hold many advantages
over EMRs. New, emerging SSR designs offer integrated
thermal protection that can prevent overheating and
improve system safety, efficiency, and longevity. This
product evolution will undoubtedly change the game in
thermal protection for a wide range of applications. ECN