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Anonymous users2024-02-13In the actual operation of the motor, such as dragging the production machinery to work, if the machinery is abnormal or the circuit is abnormal, the motor will be overloaded, the speed of the motor will decrease, the current in the winding will increase, and the winding temperature of the motor will increase. If the overload current is not large and the overload time is short, and the motor windings do not exceed the allowable temperature rise, this overload is allowed.
However, if the overload time is long and the overload current is large, the temperature rise of the motor winding will exceed the allowable value, which will make the motor winding age, shorten the service life of the motor, and even burn the motor winding in serious cases. So, this overload is something that the motor can't withstand.
Thermal relay is a protective appliance that uses the thermal effect principle of current to cut off the motor circuit when there is an overload that the motor cannot bear, and provides overload protection for the motor.
Technical data of thermal relays:
The main technical data of a thermal relay is the setting current. The setting current is the maximum current that passes through the heating element over a long period of time without causing the thermal relay to operate. When the current passing through the heating element exceeds 20% of the setting current value, the thermal relay should operate within 20 minutes.
The setting current of the thermal relay can be changed by the setting current knob. When selecting and setting the thermal relay, it is necessary to make the setting current value consistent with the rated current of the motor.
Since the thermal relay is activated by heat, the thermal inertia is large, so even if the current through the heating element exceeds the setting current several times in a short time, the thermal relay will not act immediately.
Only in this way, when the motor starts, the thermal relay will not act due to the large starting current, otherwise the motor will not be able to start. On the other hand, if the current exceeds the setting current, it will not be much, but it will act after a long time.
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Anonymous users2024-02-12How does a thermal relay work? What is the difference between manual and automatic?
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Anonymous users2024-02-11Thermal relaysWorking principle and function:
When the thermal relay is used, the thermal relay needs to be connected in series in the main circuit, and the normally closed contact is connected in series in the control circuit, when the motor is overloaded, the current flowing through the heating element exceeds the setting current of the thermal relay, and the thermal element heats up.
As the temperature increases, the bimetal sheet is bent by heating, pushing the push plate, so that the normally closed contact is disconnected, and the control circuit is disconnected so that the main circuit is also disconnected, which plays the role of overload protection.
Thermal relay structureThermosensitive element: It consists of two coefficients of expansion.
It is composed of resistance wires on different bimetal sheets. There is a difference between the main bimetal sheet and the compensating metal sheet.
Contact system: It is composed of normally closed contacts, normally open contacts and leaf springs.
Actuator: It is composed of a guide plate, a linkage system, etc.
Reset device: It consists of a manual reset button and a reset adjustment screw.
Current setting mechanism: The cam is adjusted by the current.
and pressure springs.
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Anonymous users2024-02-10Thermal relaysThe working principle is that the current flowing into the heat element generates heat, making a differenceCoefficient of expansionWhen the deformation reaches a certain distance, the connecting rod is pushed to act, so that the control circuit is disconnectedContactorsPower loss, the main circuit is disconnected, and the overload protection of the motor is realized.
As an overload protection component of electric motors, thermal relays have been widely used in production due to their small size, simple structure and low cost.
Technical Parameters of Thermal Relays:
Rated voltage. The highest voltage value that the thermal relay can work normally is generally AC 220V, 380V, 600V.
Current rating. The rated current of a thermal relay mainly refers to the current passing through the thermal relay.
Rated frequency: Generally speaking, its rated frequency is designed according to 45 62Hz.
Setting current range: The range of setting current is determined by its own characteristics. It describes the inverse proportionality of the square of the operating time of the thermal relay to the current under a certain current condition.
The above content reference: Encyclopedia - Thermal Relay.
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Anonymous users2024-02-09A protective appliance that uses the thermal effect of an electric current to cut off the circuit.
It is used in the circuit for the overload protection of the motor, in household appliances. Thermal relay currents are divided into the following according to the mode of action
Bimetal sheet type: the use of hot bimetal sheet (two metal ridges with different expansion coefficients are rolled and welded together) heated bending to push a contact actuator and act;
Fusible alloy type: use the heat of the overload current to melt the fusible alloy when it reaches a certain temperature;
This is a thermal relay made by using the characteristic principle that the permeability or resistance value of a material changes with temperature. Among the three types of thermal relays, the bimetal sheet thermal relay has good anti-time characteristics due to its simple structure, small size, low cost, and the selection of appropriate thermal elements. As a result, it gains a wide range of applications.
The basic structure of the thermal relay is composed of a thermal element, a contact system, an action mechanism, a reset button, a setting current device, and a temperature deficit compensation element. There are two parts of the thermal element, which is the main part of the thermal relay, which is composed of a bimetal sheet and a resistance wire on the outside of the surrounding bimetal sheet. Bimetal sheets are welded together from two metal sheets with different coefficients of thermal expansion.
When used, the resistance wire is directly connected in series to the two-phase circuit of the asynchronous motor. Normally closed contacts 8 and 9 are connected to the contactor coil branch of the motor control circuit.
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Anonymous users2024-02-08Summary. Hello dear. <>
<> am honored to answer for you, thank you for your patience, for you to inquire: the working principle and function of the thermal relay: when the thermal relay is used, the thermal relay needs to be connected in series in the main circuit, and the normally closed contact is connected in series in the control circuit, when the motor is overloaded, the current flowing through the heating element exceeds the setting current of the thermal relay, the heating of the thermal element increases, the temperature rises, the bimetal sheet is heated and bent, and the push plate is pushed to disconnect the normally closed contact action, and the control circuit is disconnected so that the main circuit is also disconnected, which plays the role of overload protection。
The working principle and function of thermal relays.
Hello dear. <>
<> am honored to answer for you, thank you for your patience and wait, for you to inquire: the working principle and function of the thermal relay Zheng answer: when the thermal relay is used, the thermal relay needs to be connected in series in the main circuit, and the normally closed contact is connected in series in the control circuit, when the motor is overloaded, the current of the superheated element exceeds the setting current of the thermal relay, the heating of the thermal element increases, the temperature rises, the bimetal sheet is heated and bent, and the push plate is pushed to disconnect the normally closed contact action, and the control circuit is disconnected from the mountain and the main circuit is also disconnected, which plays the role of overload protection。
Thermal relay structure temperature sensing element: It is composed of resistance wires on two bimetal sheets with different anti-sidal expansion coefficients. There is a difference between the main bimetal sheet and the compensating metal sheet.
Contact system: It is composed of normally closed contact, normally open trembling contact and leaf spring. Action Mechanism:
It consists of a guide plate, a linkage system, etc. Reset device: It consists of a manual reset button and a reset adjustment screw.
Current setting mechanism: It is composed of a current regulating cam and a compression spring.
The landlord's "mouth" is very powerful.
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