The damage of electric motors rarely occurs instantaneously, but more often is the result of long-term "sub healthy" overload operation, which leads to slow "baking" aging of the insulation layer. SPX high quality Overload Protection Thermal Relay is the "pathologist" who addresses this progressive threat. It does not focus on instantaneous short-circuit currents, but continuously "pulses" the operating current of the motor, and through a sophisticated mechanical structure, converts the current value into heat, which is then converted into mechanical displacement. This process essentially involves reproducing the temperature rise inside the motor winding in real-time outside the body. When this' in vitro model 'shows overheating, it determines that the motor body is also in danger and immediately issues a trip command.
The customized overload protection thermal relay core is a set of bimetallic strips connected in series in the main circuit of the motor. When current flows, heat is generated, and the bimetallic strip bends to one side due to the different thermal expansion coefficients of the two layers of metal. The greater the overload current, the faster the heating and bending speed.
Bending pushes a set of linkage mechanisms, and after a period of time inversely proportional to the magnitude of the overload current, it ultimately triggers the normally closed control contact to open. For example, it may take several minutes to operate at 1.2 times the rated current, while it may only take a few seconds at 7 times the rated current. The Overload Protection Thermal Relay feature matches the thermal endurance of the motor, which can withstand mild overloads for a long time and require immediate shutdown in severe overloads.
The heat accumulation and dissipation process of bimetallic strips can instinctively simulate the thermal process of motor windings without any electronic programming. This type of protection based on physical laws has its reliability rooted in materials science and is not affected by software failures or electromagnetic interference.
For the "chronic overload" of motors running for a long time at 105% -150% rated current, electronic devices may overlook it due to setting or signal fluctuations, but the heat of thermal relays will continue to accumulate until reliable operation, specifically to deal with this easily overlooked insulation chronic killer.
When there is a phase failure or severe three-phase imbalance, the operating winding current will increase significantly. High quality Overload Protection Thermal Relay, through its internal differential amplification mechanism (such as differential guide plate), can significantly accelerate the tripping action and provide effective phase failure protection.
No need for auxiliary power supply, simple structure, made of metal and engineering plastic. This means that the Overload Protection Thermal Relay has unparalleled survival and stability in harsh industrial environments with high dust, humidity, large temperature differences, and strong electromagnetic interference, which electronic devices cannot match.
Wholesale high quality Overload Protection Thermal Relays from our factory. They often exhibit an increase in mechanical resistance and a steady rise in current, making them a typical scenario for thermal relays to leverage their "chronic overload" protection advantages.
A large number of standardized small and medium-sized equipment manufacturers label thermal relays on their products to achieve the best balance between reliability and cost.
Motors in cement plants, mines, and casting workshops have high vibration and dust, and the passive mechanical structure of thermal relays shows strong adaptability.
Overload Protection Thermal Relay, as a proven standard component, is a direct and reliable choice for replacing similar products in old systems.
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