Adjustment of setting current of thermal relay

The setting current of the thermal relay: the load does not work with the rated current for a long time.

Regulation: thermal relay thermal relay has a knob setting current, with a screwdriver to spin to the current pointer position can be required, the general load rated current value, taking into account the sometimes instantaneous overload, optional load current at 1.05 to 1.2 times.

The setting current of the thermal relay is adjusted to 1-1.15 times the rated current of the motor. Relay manufacturers

The thermal element of the thermal relay has a thermal inertia, and the action of the thermal relay contact takes a period of time under the action of the overload current. This is the thermal relay protection. Therefore, the motor is allowed to run reasonably overload.

Based on the protection characteristics, the setting current of the thermal element is normally set to be equal to the rated current of the motor. But if the motor drive is the impact load, or start time is longer, or the device is not allowed to drag the parking, can be adjusted to the motor rated current 1.1-1.15 times.

The setting value of the thermal relay is generally 1~1.05 times the current of the relay when the load is working. This current may be either a line or a phase current. The main technical data of the thermal relay is the setting current. The setting current is the maximum current that passes through the heating element for a long time. When the current through the heating element exceeds 20% of the setting current value, the thermal relay should act in about 20 minutes. The setting current of the thermal relay can be changed by adjusting the current knob. When selecting and setting the thermal relay, it is necessary to adjust the current value to the rated current of the motor.

Because the thermal relay is heated and moves, the thermal inertia is larger, so that the thermal relay can not act immediately even if the current of the heating element is a plurality of times more than the fixed current in a short time. Only in this way, when the motor starts, the thermal relay will not move because of the large starting current. On the other hand, if the current exceeds the set current is not much, but a long time will move. It can be seen that the function of the thermal relay and the fuse is different, the thermal relay can only be used for overload protection and short circuit protection, and the fuse can only be used for short circuit protection and can not be used for overload protection. In a more complete control circuit, especially the larger capacity of the motor, the two protection should have.