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    Tag: relay

    How to Prevent a Spark at Relay Contacts?

    The relay contacts’ jumping or switching on/off will cause the change of inductive load and further gas discharge. The current of relay contact on-off is small, there will be no electrical arc between contacts, but there will be a spark at the relay contacts. Due to the existence of inductance in the contact circuit, there will be overvoltage on the inductance when disconnecting the contact circuit. Together with the voltage supply in the contact gap, the contact gap that just separates a little will be broken down and discharged. Limited to energy, there will only be spark discharge. The conversion of capacitance between contacts and energy in inductance makes spark discharge disappear and reappear, becoming a high frequency signal, which will be crosstalk to related circuits by means of high frequency radiation, wire transmission and distributed capacitance, forming interference signals. Furthermore, spark discharges can also damage relay contacts and shorten the service life of contacts, so that sparks may ablate contact surfaces and make the surface uneven, resulting in failure of relay poor contact.

    Difference Between Relays and Transistors

    Relays and transistors have a similar basic function, that is, both play roles of electronic switches. However, relays and transistors are very different from each other. Now let’s take a quick peek at the differences between relays and transistors.

    Safety Relay Working Principle

    Safety relay can be classified into electromagnetic safety relay, thermal reed relay and solid-state relay. The working principle of safety relays can also be roughly divided into three types. Safety relay is composed of several relays and circuits, so as to supplement each other's abnormal defects and achieve the complete function of relay with correct and low faulty operation, so as to make the error and failure value become lower, thus reaching higher safety factor. Therefore, multiple safety relays should be designed to protect different grades of machinery. It is used to mainly protect the mechanical operators who perform operation under different levels of risk.

    How to improve the reliability of a relay?

    electromagnetic relayIn addition to comprehensive parameter testing and effective screening of relays, proper use of relays is also an effective way to improve the reliability of relays. Conversely, improper use will shorten the life of the relay. How to improve the reliability of the relay? Here are some suggestions for your reference.

    • Reasonable selection of the working voltage of the relay
      The pull-in voltage of the relay is generally only one-half to two-thirds of its rated working voltage. However, when using the relay, it must work at its rated working voltage, but not the pull-in voltage as the working voltage. This is because, under the condition of the pull-in voltage, although the relay has been operated, the pressure between the moving contacts has not reached the specified value, which will cause the contact resistance between the contacts to be too large, if the contact at high current conditions, when working, it will increase the contact power, which will easily lead to contact ablation and shorten the working life.
    Difference between Contactor and Relay

    A contactor is mainly used in a primary loop, which can go through a large current (several hundred to about one thousand Amps). While a relay is used in a secondary circuit to achieve various control functions, which can only go through a small current (several to decades Amps). Functions, contacts opening and closing situation of the two subject are different.