What is the detection principle of temperature relays?

Detection principle: the temperature relay due to the temperature rise of the surrounding environment or the current heat generated by itself and the action occurs, because the on-resistance of the relay is very small, so the temperature rise caused by the current thermal effect is also very small, and the temperature rise of the ambient temperature is negligible, so it is generally achieved by controlling the change of the ambient temperature to achieve the detection of the action temperature and the recovery temperature of the temperature relay.

According to the provisions of GJB1517-92 "General Specification for Thermostatic Relays", there are three methods to choose from for the detection of temperature characteristics (i.e., operating temperature and recovery temperature), namely liquid determination method, air determination method and test block determination method. These three methods have their own characteristics, in terms of accuracy, the liquid method is the highest, the air method is the second, and the test block method is the worst, but in terms of operational simplicity, it is just the opposite. Generally speaking, if it is used to control the surface temperature of the controlled object at room temperature, the test block method is used; If the product to be tested is sealed and will not be contaminated by oil, the liquid method is used; If the product is placed inside a heated object or enclosure, the air method should of course be used.

In this system, we decided to use the air measurement method after comprehensive analysis and full consideration of the actual characteristics of the products to be tested and the technical requirements put forward by the manufacturer.

A relay that acts when the outside temperature reaches a given value. The product is a pass-contact induction sealed temperature relay, which has the characteristics of small size, light weight, high temperature control accuracy, and strong versatility. It is the most widely used product for temperature control and overheating protection in aerospace, surveillance camera equipment, motors, electrical equipment and other industries.

Principle: The temperature control switch of the temperature sensing component is used as the bimetal sheet, when the electrical appliance is working normally, the bimetal sheet is in a free state, and the contact is in a closed and disconnected state, when the temperature reaches the operating temperature, the bimetal sheet is heated to produce internal stress and act quickly, open the closed contact, cut off the connected circuit, and thus play a role in temperature control. When the appliance cools down to the reset temperature, the contacts automatically close and open, returning to normal working condition.

1. When the contact temperature sensing installation is adopted, the metal cover should be close to the installation surface of the controlled instrument, and in order to ensure the temperature sensing effect, the temperature sensing surface should be coated with thermal conductive silicone grease or other thermal conductive medium with similar performance.

2. Do not collapse, loosen or deform the top of the cover during installation, so as not to affect the performance.

3. Do not let the liquid penetrate into the inside of the thermostat, do not crack the shell, and do not change the shape of the external terminal at will.

4. The product is used in a circuit with a current of no more than 5A, and the cross-section of the copper core should be selected as 05-1 2 wire connection; For use in circuits with a current of no more than 10A, the copper core cross-section should be selected for wire connection.

5. The products should be stored in a ventilated, clean, dry and non-corrosive warehouse with a relative humidity of less than 90% and an ambient temperature of less than 40.

The functions are the same, but the output terminals and parameters are different, and each has a wiring diagram, and the reason is the same, as long as you understand one and the other are similar.

That is, when the temperature is higher (or lower) than a certain temperature, the relay acts, whether it is connected to the normally open contact or normally closed depends on the actual application.

The punctuation is not standardized, the typing is wrong, and the average person really doesn't know what you're talking about?

When the motor has an overload current, the temperature rise of the winding will be too high, and the use of heating elements can indirectly reflect the temperature rise of the winding, and the thermal relay can play the role of motor overload protection. However. Even if the motor is not overloaded.

Due to the increase of grid voltage, it will also lead to an increase in the loss of the core of the motor and cause the core to heat up, which will also make the winding temperature rise too high or the ambient temperature of the motor too high and poor ventilation. It will also cause the winding temperature to be too high, and when the latter two situations occur, it is powerless to use thermal relays. For this reason, there are relays that operate according to the temperature principle, which are called temperature relays.

The temperature relay is a miniature overheat protection component that is very sensitive to temperature changes, which can be mainly buried in the heating parts of the motor, such as the stator slot of the motor, the end of the winding, etc. It can directly reflect the heating situation at the place, whether it is the temperature increase caused by the overload current of the motor itself, or the temperature increase of the motor caused by other reasons, the temperature relay can play a protective role. It is not difficult to see that the temperature relay has a "total thermal protection" effect.

Moreover, the temperature relay can also be used for overheating protection under abnormal conditions of other electrical equipment and for temperature control of the medium.

There are generally two types of temperature relays, one is a bimetal chip type and the other is a thermistor type temperature relay.

A relay that acts when the outside temperature reaches a given value, Zhenrui Electromechanical has a relay.

When the temperature rises to a certain value, the bimetal sheet will be due to the expansion and elongation of the lower metal, and the expansion and elongation of the upper metal will be small and produce an upward bending force, and the bending to a certain extent can drive the electrical contact to realize the function of connecting or disconnecting the load circuit; When the temperature is lowered to a certain value, the bimetal sheet gradually returns to its original state, and when it recovers to a certain extent, it will drive the electrical contact in reverse to realize the function of disconnecting or connecting the load circuit.

Temperature sensor: outputs an analog signal or a digital signal and supplies it to the signal processor to display and record the obtained temperature value.

Temperature relay: The output is a switching quantity, when the set temperature is reached, the switch is acted, to control the external device.

When the temperature rises to a certain value, the bimetal sheet will be due to the expansion and elongation of the lower metal, and the expansion and elongation of the upper metal will be small and produce an upward bending force, and the bending to a certain extent can drive the electrical contact to realize the function of connecting or disconnecting the load circuit; When the temperature is lowered to a certain value, the bimetal sheet gradually returns to its original state, and when it recovers to a certain extent, it will drive the electrical contact in reverse to realize the function of disconnecting or connecting the load circuit. The working principle of the dish-shaped bimetal sheet is shown in Figure 1, the initial state is 1 (at room temperature), and after being heated (or cold), it jumps to state 2, resulting in a displacement of 3

Aviation temperature relays and civil temperature relays are basically the same in terms of working principle, but the aviation industry due to the harsh working environment, complex equipment structure, etc., has extremely strict requirements for the selected devices in terms of materials, processes, tests, service life, etc., such as the production of products need to pass a series of tests such as environmental three prevention (damp heat, mold, smoke), vibration (sinusoidal, random), acceleration, impact, low air, etc., for the life of the product is required to be the same machine with the same life. The process requires a long period of stable treatment, etc.

This paper introduces the working principle of thermal relays and the principles of correct selection.

Generally speaking:

Temperature relay: refers to the device you mentioned above, that is, the device that can complete the temperature sensing and control the on-off of the circuit itself.

Temperature sensor: Generally, only the temperature can be inducted and a change signal can be transmitted, such as resistance, voltage, current change, to be connected with a certain controller, in order to complete the circuit control, complex, but the accuracy should be high.

Thermal relay: generally used inside the air switch, or the lower end of the motor contactor, when the circuit current is slightly larger, it is not enough to jump the air or contactor, but the time is very long, it will affect the electrical appliances, it will disconnect the control circuit, its internal structure and bimetal temperature relay is the same principle, so the thermal relay and temperature relay are actually the same thing.

It is a thermistor sensor, and the three are placed in the three-phase winding part of the motor and connected in series.

He selected the model according to the insulation grade of the motor, and the winding temperature reached the upper limit of the thermistor, and the resistance value of the thermistor rose sharply, with the matching overheat protector. Cut off the power and give an alarm.

The resistance of PT100 varies linearly with temperature, which is proportional. Unlike thermistors, the resistance has a sharp turn.