Relay | Electrical Characteristics of Relays

By March 2, 2020Article

Electrical Characteristics of Relays – Different types of relays have different electrical characteristics and other characteristics. The common electrical characteristics of the general relays are as follow:

Electrical Characteristics of Relays

  • Rated Coil Voltage:

The basic electrical characteristics of a relay are the rated coil voltage. The voltage at which the relay is made operational is called the rated coil voltage. It can be also said that the input voltage to the relay is called the rated coil voltage. The rated coil voltage is set up by the manufacturer and the different relays have the different rated coil voltage. 

The coil of the relay is a sensitive part and if the voltage provided to it is exceeded then the coil of the voltage is damaged. 

  • Set Voltage:

The minimum voltage at which the switching operation is performed by the relay is called the set voltage. This voltage is also termed as the operating voltage. The set voltage or the operating voltage of the relay is always less than the ideal coil voltage. The value for the set voltage is predefined by the manufacturer. Different relays have different set voltages.

  • Rated Power:

The maximum power that a relay can handle is called the rated power. If a normal operating voltage of a relay is 60W then the rated power for the relay will be less than 60W. The power consumption of the coil is called the power rating of the coil. The power of the coil should not be more than the rated power. The power of the relays is expressed in milli-amperes and ampere ratings.

  • Switching Capacity:

The maximum value of the current which the contacts of the relays can withstand is called the switching capacity. The switching capacity can be also defined as the capacity at which the switching operation is performed by the relay. The switching capacity is defined for the loads with resistive nature which are connected with the contacts of the relays. Different relays have different switching capacity. 

Problems and Status:

Omron Relay Series 4

Omron Relay Series 4

There are numerous problems asserted with the relays. The different problems asserted with the relays are:

  • Capacitive Noise:

The capacitive components are used in the different relay loads which cause the capacitive noise in relays. The capacitive noise is avoided in the relay with the help of the proper solution. Different manufacturers of the relays use different approaches to reduce the capacitive noise for the better operation of the relays.

  • Long AC Signal Cables:

The long cables of the Ac signals cause a big problem in the relays which is the interference in the relay. The different inferences in the relay due to the long cables lower the switching capability of the relays.

  • Solutions:

The diode circuit is used in the relays to overcome the issue of the leakage current and the directional flow in a relay.

  • Leakage Current:

The other issue or problem asserted with the relays is the leakage current. The leakage current in relays is prevented with the help of the snubber circuits. The relays are manufactured to withstand the leakage current and the capacitive noise.

  • High Frequency Suppression:

The RC circuit is use in the relays for the solution of the high frequency suppression and the transient in the relays. The interference in the relays is observed with the RC circuit used in the relays design.

  • Hysteresis and Switching Points:

The switching point of the relay should be clearly separated. The different relays have the different hysteresis and each relay has its own efficiency for the hysteresis. The electromechanical relays are the relays with the strong hysteresis and switching points while the other relays have the lower hysteresis. 

The best switching points are observed in the relays. In the relays the hysteresis circuit is used to find the switching point.  The relays with the optocouplers have the weakest hysteresis.  

  • Status Indication:

A LED is used to indicate the status of the relay. The LED used for the indication of the relay is not a proper status indicator as it gives the wrong results in different conditions. The 100% status indication is available in the relays. The different current hysteresis are used in the manufacturing of the relays.  

  • Short Lifetime of Relays:

The frequency at which the relay is switched and used determines the lifetime of the relay. The real load of the relay is used to estimate the lifetime of the electromagnetic relays. 

The relays which are used in the systems with frequent switching have shorter lifespan as compared to the relays which are used in the systems where switching is not frequent. The different parameters of the relays are used to improve the lifetime of the relay.


Related topic:

Relay | Structure of Relays and Operating Principles


Operating Forms:

The relays differ from each other in the operating form. One relay is specific in its operation and it follows it particular operation form. Similarly, another relay will follow its own specific operation form. The basic operation forms of the relays are:

  • Electromagnetic Relays:

The operating form of the electromagnetic relay is the electromagnet used in the structure of the relay. The electromagnet connects and disconnects the contacts of the relays for the switching purpose. The coil used in the electromagnetic relay is activated and deactivated with the help of electromagnetic which is the main component in the relay.

  • DC v/s AC Relays:

The dc and the ac relays works on the same principle as followed by the electromagnetic relay. The only difference is the components used in the relays and the load connected with the relay. Freewheeling diode is used in dc relays for the activation of the coils while the ac relays use the laminated cores for the prevention of the eddy current losses.

  • Induction Type Relays:

Induction type relays are used in the ac systems which have circuits which need to be protective. Induction type relays are basically the protective relays. The moving conductor is used in such relays. The electromagnetic fluxes are not desirable in such relays.

  • Magnetic Latching Relays:

In this type of relays, the permanent magnets are used for the operation of the relays. The magnets used in such relays are with the high remittance. The high remittance of the coil is useful for the placement of the armature and the power coil.

  • Solid State Relays:

The components used in the solid states relays are the solid state relays. The solid state relays are the relays which operate without the movement of the components in the relay. The solid state relays are further classified into other types based on their operating forms. The other types include the reed relay coupled SSR, photo coupled SSR and transformer coupled SSR. Each category has its own operating principle which is followed in the working of the relay.

Dimension and Shapes:

The different kinds of relays come in different shapes and dimensions. The dimension of the relay varies from manufacturer to manufacturer. The datasheet of each relay is available to study its dimension. The general dimension of the relays is about 43 * 10 * 25 mm. 

The shapes for the relays also vary from the manufacturer to manufacturer. The common shapes of the relays are rectangular. The selection of the relay dimension and the shape is based on the choice of the user according to the circuit or the panel where the relay is being used. 



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