Thermal relay setting current: The current at which the thermal relay does not operate for a long time when the load is operating at rated current.

Adjustment of thermal relay: The thermal relay has a knob to adjust the set current. It can use a screwdriver to rotate the pointer to the desired position at that time. Usually the rated current value of the load. Considering instantaneous overload, 1.05 to 1.2 times the load current can be selected.

The setting current of the thermal relay is adjusted to 1-1.15 times the rated current of the motor. The thermal components of thermal relay manufacturers have thermal inertia. Under the effect of overload current, the action of the thermal relay contacts takes some time. This is the maintenance characteristic of thermal relays. Therefore, reasonable overload is allowed during the operation of the electric motor.

Based on maintenance characteristics, the set current of the thermal element is usually set to be equal to the rated current of the motor. But if the motor is driven by an impact load, or the starting time is long, or the equipment does not allow shutdown, the rated current of the motor can be adjusted to 1.1-1.15 times.

The setting current value of a thermal relay is generally 1-1.05 times the current passing through the thermal relay when the load is normal. The current can be either a line current or a phase current. The primary technical parameter of a thermal relay is the set current. The set current refers to the current that passes through the heating element for a long time without causing the thermal relay to operate. When the current passing through the heating element exceeds 20% of the set current value, the thermal relay should operate within 20 minutes. The setting current of the thermal relay can be changed through the setting current knob. When selecting and setting a thermal relay, the set current value should be consistent with the rated current of the motor.

Due to the heating operation of the thermal relay, it has a large thermal inertia. Even if the current passing through the heating element exceeds the set current multiple times in a short period of time, the thermal relay will not immediately operate. Only in this way, when the motor starts, the thermal relay will not operate due to high starting current, otherwise the motor will not start. On the contrary, if the current exceeds the set current, it will not be too large, but will move for a long time. Thermal relays and fuses have different functions. Thermal relays can only be used for overload maintenance and cannot be used for short-circuit maintenance, while fuses can only be used for short-circuit maintenance and cannot be used for overload maintenance. In more sophisticated control circuits, especially in larger capacity motors, these two types of maintenance should be provided.

Article source: Wholesale and customization of power relays www.jxzhongxuan.com