Cold and Hot do not refer to the ambient temperature at the installation point of the thermal overload relay. In fact, the Lovato relays are temperature compensated, so their tripping is not influenced by the ambient temperature for a range indicated in the catalogue (on average -15 ° C … + 55 ° C). Cold condition curve means that the relay has not been carrying a current for a period enough to allow the complete cooling of the tripping elements that are the bimetals. Hot condition curve means that the relay has been carrying the rated current set on the adjuster for a time enough to bring the bimetals into a condition of thermal regime. The time for complete cooling or to reach the thermal regime is around 60 minutes. So, if the relay is crossed by an overload current in cold condition, the tripping time will be longer than in hot condition. This is because in the hot condition the bimetals have already partially advanced towards the tripping point.
__________________________________________________________________
Other information on this topic
Visit the website page dedicated to Motor protection relays.
Check out our video
 |
