Thermal protectors are a category of protectors. Because they can help play a role in security, they are relatively widely used on the market. So the knowledge involved today is information about the principle parameters and actual structure of the product. Friends who are interested in purchasing reference can combine their budget needs to select the most suitable brand from the total number of products in the market, and refer to the product parameters to further purchase a thermal protector suitable for them.
1. What is the difference between thermal protector and current overload protector?
The thermal protector is protected according to temperature changes. When the appliance reaches the set temperature, the thermal protector is automatically disconnected; the current overload protector is protected according to the current change. When the appliance current exceeds the set current, the current overload protector Automatically disconnected. Their working principle is different according to different structures.
The thermal relay is based on the principle of thermal deformation of metal components. When the line current is too large and the hot metal components are deformed enough, the metal components are disconnected to control the circuit breaker trip. After the metal element cools, it will return to its original position, ready for the next action. Its action value has been set by the manufacturer.
Overcurrent protection device is realized by current relay. According to the normal operating current of the circuit, determine the operating current according to a certain overload multiple. When the line current exceeds this operating current, the normally open contact of the overcurrent relay is connected to the trip circuit and the switch trips.
Second, the principle and structure of the overload protector
Protectors are commonly used thermal relays, which consist of bimetallic thermal elements, action mechanism, normally closed contacts, normally open contacts, reset button and current adjustment knob. When the motor is overloaded, the current becomes larger, the bimetallic thermal element is deformed by a large current for a long time, and the contact is moved by the action mechanism, which causes the switch to trip and play a protective role.
The working principle of the thermal relay is to generate heat from the current flowing into the thermal element, so that the bimetallic plates with different expansion coefficients are deformed. When the deformation reaches a certain distance, the connecting rod is pushed to move, the control circuit is disconnected, so that the contactor When the power is lost, the main circuit is disconnected to realize the overload protection of the motor. As an overload protection component of the motor, the relay has been widely used in production due to its small size, simple structure and low cost.
