1. Place the temperature control switch in the drying box for testing. The air pressure in the environmental test box should not be less than 200m/min. The temperature inside the temperature field should be kept uniform (the best way is to install a heating resistor at the bottom of the drying box, and a cooling fan horizontally above the heating resistor. When the drying box is gradually heated, turn on the fan system at the same time to ensure uniform temperature inside the temperature field);

2. The liquid bubble of the thermal resistor or mercury thermometer should be close to the temperature sensor end of the protective device or as close as possible to the overload protector, and parallel to the cooling fan (the best way is to lightly tie the temperature sensor end of the protective device to the liquid mercury meter bubble, and keep the average error of the liquid mercury meter consistent with the actual cut-off value of the protective device), use a display light or other methods to indicate the conduction status, and the current of the overload protector shall not exceed 0.01A;

3. Increase the gas temperature during the experiment. When the gas temperature is about 10K lower than the rated cut-off temperature lower limit, the temperature elasticity coefficient does not exceed 0.5K/min until the overload protector is in action. Reduce the gas temperature. When it is about 10K higher than the calibration temperature limit, the temperature elasticity coefficient does not exceed 0.5K/min until the overload protector is calibrated and reconnected to the control loop (due to the different speeds of the temperature sensor of the protection device and the liquid mercury meter, too fast a temperature increase or decrease will cause inaccurate data testing);

4. When the product is being tested, there is no other object close to the temperature sensor except the liquid mercury bubble. Due to the heat absorption reaction of other objects, it is easy to cause the temperature of the protective device to lag behind. How to select a motor overload protector Today, motor overload protectors have evolved from the previous foot-operated type to electronic and fully intelligent, with high sensitivity, high stability, multiple functions and easy adjustment. The motor's current, operating voltage, temperature and other parameters can be displayed immediately. The type of problem after maintenance is clear at a glance, which greatly facilitates the identification of the problem, helps to solve the problem on the production site and shortens the recovery time.