Thus, the setting is called the “time dial setting - TDS”. This is a variation of the neutral relays. Electrical Characteristics of Relays. This value should indicate also if the current is AC or DC. This relay changes state as long as the electromagnet is actuated, and goes back into relax state when the electromagnet is not actuated any more. For two contact pairs, it would be DP as for Double Pole. Two electromagnets are placed one opposite the other. This time i want share information about relays characteristics most often used in typical automation and instrumentation work. The single-line curve, characteristic of overcurrent relays, indicates the approximate time that the device will close its contacts to initiate the opening of a circuit breaker. The characteristic curves of electromechanical relays are developed by testing. Instead, a FET or a TRIAC is used to simulate the contacts. are required to construct this protective relay.. The relay will not operate when the value of current is less than the pick value. 14 FUNDAMENTAL RELAY-OPERATING PRINCIPLES AND CHARACTERISTICS 2 FUNDAMENTAL RELAY-OPERATING PRINCIPLES AND CHARACTERISTICS Protective relays are the "tools" of the protection engineer. These relays have the most common coil. There are basically two types of relays in this category. The package: Last but not least is the package. Actually, they do not have contacts! In this context, the ever increasing presence o… Bellow i illustrate both of these contacts: You may notice that the NC contact is turned upside-down compared to the NO contact. I will illustrate the most basic types of relays: The things that characterizes a relay are the followings: The coil voltage: This is the voltage that the coil can actuate the armature. Rated Coil Voltage- The voltage that the relay is supposed to receive when you energize it.. Set (Operate) voltage- The minimum voltage that the relay needs to close its switch.This will be a little less than the ideal coil voltage. The polarization of the magnetic field of the coil depends on the polarity of the supply. There are many other types of relays like the timers and the function relays, but they use some kind of circuitry to perform different actions. The device that forces the terminal to move, is actually an electromagnet! Look at the following illustration. Another common application for reed relays is on the speed meters of the bicycles. Having this relay instead of a switch, you can turn on and off the lights with one pushbutton. This force comes from the spring. This magnetism can overcome the force of the spring and can pull the contact towards it, thus it changes it’s position! More recently static relays have been superseded by first digital relays and now numerical microprocessor based devices. Before extending to the various types of relays, i will first explain what and how the basic relay operates. Time-overcurrent relay curves marked with a star conform to IEEE C37.112-1996, “IEEE Standard Inverse-Time Characteristic Equations for Overcurrent Relays.” S&C Standard Speed Curve Type The Normal Open is a contact like the one showed in the previous illustration. 3. In this relay, the operating time is approximately inversely proportional to For safety reasons, if this happens, the relay can only be restored mechanically, if someone pulls the lever of the relay up again: Very common relays in motor applications, as well as in all electrical installations. Figure 1 shows a TCC plot of a fuse and an overcurrent relay. This type of relay operates just like a toggle flip flop. The operating temperature: The temperature that the relay can operate without problems, Switching frequency: The maximum make-break frequency. You can download the paper by clicking the button above. You may know these relays with another name… thermostats, used extensively in heating applications. Thus, if a relay has 1 contact pair (POLE), the code would be SP as for Single Pole. The characteristic curve for the relay is shown in the figure below. This is very handy in modern house lighting. Overload Relays 8 Ambient Temperature other than 40˚C For a thermal overload relay in an ambi-ent temperature higher or lower than the motor 40°C (104°F), the overload trip current can be calculated by applying a correction factor from the curve in Figure 1. (Distributed Control System), Siemens S7 1200 PLC configuration in TIA Portal, Programmable Logic Controllers Multiple Choice Questions, Three-valve Manifold on Remote Seal DP Transmitter, Pressure Temperature Compensation Flow Measurement, Communicating Delta PLC Software to Simulator. The process is done automatically according to the temperature of the bimetallic strip. pdf. Each relay curve has a time dial setting which allows the curve to be shifted up or down on the time-current characteristic curve. In this category i separate the relays according to the way that their coil is powered to actuate the armature. : 4 The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as over-current, overvoltage, reverse power flow, over-frequency, and under-frequency. Thus, the load will only operate when the relay is actuated. The current that goes through the driver must be enough to actuate the armature. The higher the gap the higher the voltage that a relay can cut-off. Find great small businesses around the corner and across the country. There are so many different types of relays, that it would be literally impossible for me to add them in this article. The first sub-type is the current-leaking protective relay, and the other type is the overload protection relay. Curves of operating time versus the magnitude of the actuating quantity. The switching frequency: This characteristic is determined by the mechanical construction of the relay. I used an octal-type relay. This can be represented graphically by the relays TCC curve (Time Current Characteristic). Double Throw (DT) means that the relay has pairs of NO/NC contact. relays. Look the following animation: A relay may have a combination of the above contacts. Thus, the curve characterizes the operation of a relay. A third parameter related to the selection of the characteristic curve of DOCR can be considered. The equation describing the Extremely Inverse Relay is I2t = K where I is operating current and t is time of operation of the Relay. For a fault current F1, the device operates at time T1. This way, both contacts (NO and NC) will change state if a force is applied to the left metal heading from UP to DOWN. You could imagine a reed relay like a relay without an electromagnet. This way, the relay is actuated only if the coil is correctly biased. If this electromagnet is powered, then the relay will be forced to break connection, as if it was overheated. Academia.edu no longer supports Internet Explorer. 2. Note that our team can also add curves for you if you provide the data. Calculate PSM of Various IDMT Relay. When the first coil is actuated, the relay goes to the SET position and it remains there no matter if this coil is kept actuated. This is the most common relay type and is used widely in automation. This is done in purpose. The IEC 60255 standard defines four standard current time characteristics – standard inverse (SI), very inverse (VI), extremely inverse (EI) and long-time inverse. Each relay has two mechanical parts inside. The difference that makes these two relay types different is that the biased relays will allow the current to flow through it’s coil, even it the relay is reverse-biased! Following is (at last) the complete illustration of the basic relay: Now, imagine that someone wants to control a 220Volts 1 K-Watt load with a command that comes from a 5 Volts battery. The devices are categorized and stored by manufacturer name and device type for easy retrieval. 2. Awesome Information, I would like to understand more about relay. On the next pushbutton press, the lights are turned off. This kind of relays operates exactly the same as the biased relays. They does not actually have an electromagnetic coil. Moreover, these relays may follow different characteristic curves, such as inverse definite minimum time (IDMT) or normal inverse (NI), very inverse (VI) or extremely inverse (EI), making the selection of TMS and PS very difficult. Keep it up. So, here is the relay opened: You can clearly see the common contact, the NO and NC contacts as well as the electromagnetic coil and the return-to-normal spring. When the contact is still, then no current flows through it (because it is an OPEN circuit). These relays does not have a coil, nor any other moving part, that’s why they are called Solid State. It will only change state (to RESET position) only if the other coil is actuated. The general code form is this: The ‘P’ stands for “POLES”. When the contacts are ‘in contact’ then the current flows from Terminal 1 to Terminal 2. Turn ON/OFF operation As in any craft, an intimate ... consider the fundamental relay types. Fig. But if the current that flows through the second electromagnet is less than the current that flows through the first electromagnet, then the armature is pulled to the first electromagnet that has greater magnetic force! 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