Electromagnetic attraction relays are of two types, namely attracted armature type and solenoid type. Protection categories Category Explanation Condition RT 0 Unenclosed relay Relay not provided with a protective case. This must be taken into consideration when designing the positioning of the relay and other semiconductor components on the PCB. In a static distance relay it is necessary that the two input quantities are similar i.e., voltage/voltage or current/current because they are not electrically separate as they are in case of electromagnetic relays (in an impedance relay magnets are energized by voltage and currents). Electromagnetic relays are those relays which are operated by electromagnetic action. Definite Time Lag Relays – In these relays, the time of operation is sensibly independent of the magnitude of the current or other quantity causing operation. The electrical protective relay can be broad, classified into two categories (i) Electromagnetic Relay and (ii) Static Relay. Within built software with predefined values: They use microprocessor. † Locate the surge suppressor for the relay coil as close to the relay as possible. In an attracted armature type relay operation depends on the movement of an armature under the influence of attractive force due to magnetic field set up by the current flowing through the relay winding. Electromagnetic Relays (also known as traditional mechanical relay, Electromechanical Relay, EMR), are widely used in many fields as the earlist relay. The performance of static relay is better than electromagnetic relays as they are fast acting and accuracy of measurement is better than electromagnetic relay. The construction of the relay is easily affected by the surrounding interference. SSRs employ semiconductor switching elements, such as thyristors, triacs, mosfet and transistors to switch the load current. These relays operate on the simple principle of split-phase induction motors. Electromagnetic Relay . Unlike solid state relays(SSR), electromagnetic relays use mechanical action components with contacts as the switching components (such as Coil-Reed Electromagnetic Relay). The relay may be defined as an electrical device interposed between the main circuit and the circuit breaker in such a manner that any abnormality in the circuit acts on the relay, which in turn if the fault is dangerous then it causes the circuit breaker to isolate and so to remove the faulty element. And have no operation zone as small load. The relay ensures the safety of the circuit equipment from any damage which might be otherwise caused by the fault. The performance of CT under short-circuit condition is also improved. It also protects the circuit current. Directional or Reverse Current Relay – The relay operates when the applied current assumes a specified phase shift on the supply voltage and the relay is compensated for the fall in voltage. The time-current characteristic of such relay is an inverse time characteristic. Distance Relay – In this relay operation depends on the ratio of the voltage to the current. Present generation relays. It is most widely used for the protection of low-voltages squirrel cage induction motors or dc motors of lower output ratings. In electrical systems, a static relay is a type of relay, an electrically operated switch, that has no moving parts. Operation of a 12 A relay. A solid stat relay uses semiconductor switches, transistors or switchable diodes (2 ea. These relays operates on the principle of thermal effect of electric current. Differential Relay – The relays operate when some specified phase or magnitude difference between two or more electrical quantities occurs. Solid State Relays vs. Electromagnetic Relays. Its operation depends on the movement of a metallic disc or cylinder free to rotate by the interaction of the induced currents and the alternating magnetic fields producing them. Relays may be classified on the basis of the electrical quantity (actuated by the voltage, current, power, etc. This relay has to be installed straight only and away from magnetic field. Jump to navigation Jump to search. Operating Principle: They use principle of electromagnetic principle. Such relays are actuated by DC or AC quantities. Electromagnetic Relay. Gravitational force can affect the relay. The controlling element manages a sudden change  in the controlled quantity such as the closing of the current operative circuit. For integrated protection and monitoring systems programmable microprocessor controlled static relays are preferred. Inverse Time Lag Relays – In this relay, the magnitude of the current or other quantity causing operation is inversely equal to the time requires for the operation. Książkiewicz A., Kamińska A., Contact bounces during closing an electromagnetic relay, Computer Applications In Electrical Engineering, 2008, p. 381- 382 Advertisement Recommended publications Protective Relays 3. replaced analogue circuits used in static relays to implement relay functions. One main difference between them is electromechanical relays have moving parts, whereas solid-state relays have no moving parts. A control relay allows electrical current to flow through a conducting coil that opens or closes a switch. Primary relays are those whose sensing elements are directly connected in the circuit or element they protect, while the secondary relays are those whose measuring elements are connected to the circuit they protect through instrument transformers. Basic design and operation. † Keep the relay and semiconductor components as far away as possible. RT I Dust protected relay Relay provided with a case which protects its mechanism from dust. There are two basic classifications of relays – Electromechanical Relays and Solid State Relays (Static relay). Torque Slip Characteristic of an Induction Motor, Difference Between Serial and Parallel Communication, Potier Triangle or Zero Power Factor Method, Two Wattmeter Method of Power Measurement, Difference Between Conduction and Convection, Difference Between Circuit Switching and Packet Switching, Difference Between Static and Kinetic Friction, Difference Between Ductility and Malleability, Difference Between Physical and Chemical Change, Difference Between Alpha, Beta and Gamma Particles, Difference Between Electrolytes and Nonelectrolytes, Difference Between Electromagnetic Wave and Matter Wave. Low CT burden – The VA consumption of static overcurrent relays is quite low (7 mVA to 100 mVA) as compared with that of electromagnetic relays (1VA to 3VA) so that smaller CTs are required. An electromagnetic relay is a switch that is turned on and off by a magnetic field. According to the principle of operation and construction, the relay may be classified such as the electromagnetic attraction type, electromagnetic induction type, electrodynamic type, moving coil type, electro-thermal type, physics electric type, and static relays. Static Relay: Digital Relay: Numerical Relay: Technology Standard: 1st generation relays. With a control relay, users do not need to manually turn the switch to isolate or change the state of an electric circuit. Do You Want To See More Details About "comparison of electromagnetic relay vs static relay vs numerical relays"? In this relay, the magnetic coil freely rotates in the magnetic field of a permanent magnet. 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