Signal Relay
Power Relay
Automotive Relay
The role and choice of relay
                                                                           And its major role in relays
Relay is a separate function of the automatic switching components are widely used in remote control, telemetry, communications, automation, mechanical and electrical integration, and power electronic devices, is one of the most important control elements.
.... Relays are generally able to reflect a certain input variables (such as current, voltage, power, impedance, frequency, temperature, pressure, speed, light, etc.) of the sensor body (enter the part); there can be accused of circuits "Tong", "off" control of the implementing agency (output part); in the input section and output relays between the parts, there is coupled to the input isolation, functional processing and the output to drive in the middle part of the body (driver section).
.... As control components, sum up, relays the following several functions:
..... 1) Expansion of control. For example, the multi-touch relay control signals to reach a certain value, can be different forms of contact groups, while for then, open break, connected to multiple circuits.
.... 2) to enlarge. For example, the sensitive relay, intermediate relays and so on, with a very small amount of control that can control on the power circuit.
..... 3) Integrated signals. For example, when multiple control signals required in the form of input multi-winding relay, when, after a more integrated, to achieve the intended control effect.
.... 4) automatic, remote control and monitoring. For example, the automatic device on the relay, together with other appliances can be composed of process control lines, in order to achieve automated operation.
                                                                            Relay selection

Selection of a per-use environment for
... The use of environmental conditions, mainly refers to the temperature (maximum and minimum), humidity (usually 40 degrees Celsius with a maximum relative humidity), low pressure (using a height of 1000 meters from time to consider), vibration and shock. In addition, there are packages, installation methods, such as shape size and insulation requirements. Because of different materials and structures, mechanical relays to withstand the environmental conditions vary over product standards prescribed under the conditions of the use of environmental mechanics, it is possible damage to relays, mechanical condition of the environment can be machine or high-level conditions for use.
... Electromagnetic interference or radio frequency interference on the more sensitive the device around, the best incentive not to use AC relay. DC relay to be selected with a choice of coil transient suppression circuitry products. Solid-state devices or circuits that provide incentives and more sensitive to the peak signal to the local, but also choose a transient suppression circuitry products.

7.2 according to the input signal to determine the different types of relays
... According to the input signal is electrical, temperature, time, light signals to determine use of electromagnetic, temperature, time, photoelectric relays, there is no problem. Here we must especially note voltage and current selection of relays. If the machine is a constant supply of relay coil current should use current relay, is a constant voltage value is selected voltage relays.
7.3 Selection of input parameters
... With the user input volume is closely related to the work coil voltage (or current), while the pull-in voltage (or current) is the relay control relay manufacturer, and its sensitivity to judge, assessment parameters. The user is concerned, its just a working parameter values under the limit. Control of the security factor is voltage (current) / pull-in voltage (current), if the value used in the pull-in relay, is unreliable, unsafe, environmental temperature increases or in the vibration, shock conditions, will Relay work is not reliable. Machine design, can not be no-load voltage as the relay operating voltage basis, but rather access to the coil as the load to calculate the actual voltage, in particular, especially the power resistance is large. When using transistor as switching elements control the coil off, the transistor must be in the switch state, the following tasks on 6VDC voltage relay is concerned, shall also deduct the transistor saturation voltage drop. Of course, not work values increases as high as possible, over rated too high will increase the value of the impact of the armature wear, increasing the number of contact bounce, reduce electric life, in general, the working value of pull-in value of 1.5 times the value of work The error is generally 10%.
7.4 depending on the load to choose the type and capacity of relay contacts
Practice has proved that a long time ... at home and abroad, about 70% of the failures occurred in the contact, the This shows that the correct choice and use of relay contacts is very important.
... Combination of form and contact number of contact group charged with loop should be based on actual conditions. Commonly used form of contact combinations in Table 6. All contact group and the dynamic transformation of the dynamic contact group co-contact right, because when connected to a small number of contacts and contact bounce of compensation after ablation of a large amount of its load capacity and reliability of the more dynamic off-contact exposure group and the conversion of the dynamic contact groups want to touch off a high, the whole line can be adjusted to the contact position, as many as possible together with the fixed contact.
... Depending on the load size and load capacity of nature (resistive, inductive, capacitive, lamp set and the motor load) to determine important parameters. That the contact switch load switch small loads must be better than big and reliable is not correct, generally speaking, relay switching load at rated voltage and current greater than 100mA, less than 75% of rated current best. Current is less than 100mA will contact coke increased, decreased reliability, and therefore called the test current of 100mA, is home to professional standards of the relay manufacturer assessment process conditions and the level of the content. As the general-purpose relays do not have low-level switching capability for switching 50mV, 50A load relays the following order, the user must specify, if necessary, should be invited to help plant selection relays.
... Relay contacts rated load and service life is defined as rated voltage, current, resistive load of the action times, when beyond the rated voltage, it can refer to the load curve selected contact. When the load changes the nature of their contacts with variable load capacity will occur, the user can refer to Table 1 Transform contact load current.

Table 1

Resistive current

resistive current

motor current

lamp current

minimum current






Relay jacket marked only resistive rated load value, and the other the nature of the rated load please refer to technical conditions, the surge current size

table 2


Surge Current

Surge Time


Resistive steady

state current


L 10-4H or cos = 10-0.01


10~20times the steady-state current of


should be regarded as inductive load, but when = L / R <10-4S can be considered as a resistive load when


5~10times the steady-state current


can be 5 to 6 times the current of resistive load in place of test

White light

10 to 15 times steady state current




about three times the steady-state current




5 ~ 10 times the steady-state current



Sodium lamp

1 ~ 3 times the steady-state current



Capacitive load

20 to 40 times steady state current


long transmission lines, filters, power class should be considered as capacitive load


3 ~ 15 times steady state current



Electromagnetic contactor

3 ~ 10 times the steady-state current



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