high leg delta vs wye

A delta-wye transformer is a type of three-phase electric power transformer design that employs delta-connected windings on its primary and wye/star connected windings on its secondary. There exist long, complicated equations for converting between Y and Delta resistor networks, but there is a much simpler solution to this problem than that! You can look up split-phase delta (aka wild leg, high leg...), grounded delta, open delta. Of course, this is not the only way these three transformers could be connected in a Y-Y configuration. If not, you will find the answer in this demonstration. 240/120 high leg system to a 480Y/277 system—existing 240/120 panels still need to be fed. VAB = 240 volts VBC = 240 volts VAC = 240 volts, VAN = 120 volts VBN = 208 volts VCN = 120 volts. Tags: delta, three phase, Wye No – a three-phase “Wye” buck-boost transformer connection should be used only on a 4-wire source of supply. The usefulness of this connection scheme should be clearly evident: three different voltage levels may be accessed for use in powering circuits. What general calculation may be applied to balanced, Y-connected systems relating phase and line voltages? Discuss the advantages and disadvantages of such a configuration with your students. Unlike the delta transformer, it doesn't have a high leg. OK, but I was addressing what appeared to me to be a global comment that if it's three phase with a neutral it must be a wye. If THAT transformer has a Neutral, it's a Wye secondary. One of the conductors connecting the secondary of a three-phase power distribution transformer to a large office building fails open. If not then it is most likely delta. need to first be able to identify the differences between single-phase and 3-phase power distribution Possible solutions in the past have been to: † Separate the Usually, the coils shown are secondary windings of three different transformers, the primary windings connected to a set of three-phase high voltage power lines. Many call it a high-leg system because the voltage from Line 2 to ground is higher than that of the other legs. For example, a 120V delta transformer will have a 208V leg (Figure 12–1). Differences in wye and delta transformers. Though one can be provided, which is called a high leg. For example, a 120V delta transformer will have a 208V leg (Figure 12–1). You must log in or register to reply here. Is there a neutral at all? It is used when both single and three-phase power is desired to be supplied from a three phase transformer (or transformer bank). What conditions typically cause a polyphase system to become unbalanced? If it has a neutral it could be a delta/high leg system. Because the system is only, in essence, capacitively coupled to ground through a relatively high impedance, the entire system is. Magnetic fields are harmless Notes 14 Understanding the open-Delta configuration is made easier if students first understand the robustness of If there is a neutral all line to neutral voltages will be the same (or at least very close to same) if it is a wye system. Don't assume that the high leg will be 208 to ground. This type of wiring may also be beneficial for Context. Ive never seen a high leg system in Canada. This scenario is all too common in modern power systems, as non-linear loads such as switching power supplies and electronic power controls become more prevalent. Based on this observation, what do you think caused the failure? 01.4TB.113 Open Delta or a Wye Connected Voltage Transformer – Which One Should You Choose? A neutral wire can be provided on wye output side. 10 and 12 Lead High-Wye Available Voltages 10 lead generators are identical to 12 lead generators with the exception that T10, T11, and T12 are permanently bonded together as T10 or T0 480V Connections shown in Blue 416V These transformers are connected in an open-Delta configuration. 3 phase delta power Most utility companies will not hook up 3 phase delta on the customer side anymore because the the “high” or “wild” leg, which as shown in the diagram runs a good deal higher than 120 volts to neutral. Here’s a hint: if you were to repair the neutral wire and take current measurements with a digital instrument (using a clamp-on current probe, for safety), you would find that the predominant frequency of the current is 180 Hz, rather than 60 Hz. Fig. Wye system would be 600/347 volts. Published under the terms and conditions of the Creative Commons Attribution License. If it is a 4 wire delta, one line will be significantly higher voltage to neutral. Wiring arrangements can have a considerable effect on output voltage. Explain both answers, in terms that anyone with a basic knowledge of electricity could understand. The Wye and Delta three phase configuration each have their uses. It can be a single three-phase transformer, or built from three independent single-phase units. In a delta-delta xfmr, it is (remotely) feasible that the failure of any one leg will allow limping along with a two phase open delta. three-wire circuit used in a three-phase electrical system in which three elements resemble a triangular arrangement of electrical three-phase windings Explain the difference between a balanced polyphase system and an unbalanced polyphase system. In a balanced Y-connected power system, calculate the phase voltage (Ephase) if the line voltage (Eline) is 480 volts. A delta to Wye connection does not provide adequate current capacity to accommodate unbalanced currents fl owing in the neutral wire of the 4-wire circuit. I think the 240 volt Delta is better if you have a lot of motor loads but the high leg is a pain, especially for DIY's and hacks that learn the “I don’t know of a book which clearly explains Delta vs Wye in terms of magnetic fields and ground current. ): These transformers are connected in a Y-Delta configuration. It is called “three-phase” because it consists of three sinusoidal voltages; these voltages have the same amplitude and frequency, but they are 120° out of phase relativ… There is 208 Volts from line-to-line. Figure 3 is the schematic for a Delta/Wye configuration. Where it matters is at the incoming service transformer. Ask your students which type of three-phase system (balanced or unbalanced) is easier to analyze, and why that is so. This type of wiring may also be beneficial for This is the most common four-wire three-phase delta service and is essentially a 240 volt, three-phase, three-wire delta service with one of the 240 volt transformer winding center tapped to provide two 120 Vac circuits, which are 180 degrees out of phase with each other. Special instruments exist to measure harmonics in power systems, but a simple DMM (digital multimeter) may be used as well to make crude assessments such as the one described in the Answer. But if you can get that far into it, you can likely just read the nameplate to see it anyway. Where it matters is at the incoming service transformer. Though one can be provided, which is called a high leg. Calculate all voltages, currents, and total power in this balanced Y-Y system: Calculate all voltages, currents, and total power in this balanced Delta-Y system: Calculate all voltages, currents, and total power in this balanced Y-Delta system: What resistor values would we have to choose in a Delta configuration to behave exactly the same as this Y-connected resistor network? Wye/Delta is used in high voltage transmission, and Wye/Wye is seldom used because of potential unbalance. The voltage measured from this center tapped neutral to the third “wild” leg is 208 Vac.This service almost always has a neutral connection, but in some rare situations, the neutral conductor is not available. I've seen plenty of high leg delta's but until a few weeks ago had never seen one on a house here. Ask your students what these results indicate about the reliability of Y versus Delta source configurations. Hook As for the 'center tap' in the asker's text, IMO that is the terminal in the middle. In the U.S., the ratio of high and low voltage is 2:1 (460 volts:230 volts), but in Europe, it is √3:1 (380 volts:220 volts). What is strange, though, is that the overheated wire is the neutral conductor, not any one of the “line” conductors. Probably a local electrical There is more than one place to start in determining the solution here, and more than one way to calculate some of the figures. Y-Y, Y-Delta, Delta-Y, etc. Easy understanding of 3-phase transformer connections - Delta–Delta, Wye–Wye, Delta–Wye and Wye–Delta (on photo: Jefferson Electric transformer) While three-phase devices are usually the more cost-effective option, the single-phase option provides more versatility and can be attractive from a reliability and maintenance standpoint . In a delta-wye ungrounded xfmr, the failure of any one leg means you loose too much to limp along. FYI the high leg should be … Photographs of transformer connections may also be used in the classroom to provide practical examples of this concept. Challenge your students to solve this problem without resorting to the use of one of those long conversion formulae. 3-phase power systems: Y (Wye) and Delta With a 3-phase supply you have two ways of connecting a traditional 2-wire load, such as a light bulb or a server. Do you know the transformer rule that applies to Wye-Delta banks? Understanding the open-Delta configuration is made easier if students first understand the robustness of the regular Delta configuration: how it continues to provide true three-phase power with no degradation in line voltage in the event of a winding failure. In the Y-Y system, with no neutral wire, one of the load phases will completely lose power, while the voltages of the other two load phases will be reduced to 86.7 % of normal. With a 208/120V system, there is no high leg. In this case, the 5–10% 120 capacity does not meet upgrade requirements. A 600 volt delta with high leg would be 300 to neutral JavaScript is disabled. Being that pole-mounted power distribution transformers are exposed for anyone to look at, they provide an excellent opportunity for students to practice identifying three-phase connections. No matter how your students may have approached this question, though, they should all obtain the same answers. Calculate all voltages, currents, and total power in this balanced Delta-Delta system: Be sure to ask your students to describe how they arrived at the answers to this question. If there are any such transformer configurations located near your campus, it would be an interesting field exercise to bring students there (or send them there on “field research”!) Most here if they are three phase are wye not delta. In a wye configuration, there is no high leg (hence the 'if any' in the text). Y-Y, Y-Delta, Delta-Y, etc. Upon inspection, the source of the failure is obvious: the wire overheated at a point of contact with a terminal block, until it physically separated from the terminal. Delta-Delta: A Delta-Delta configuration is recommended for projects that does not need a neutral on the secondary side. • Delta-Delta: A Delta-Delta configuration is recommended for projects that does not need a neutral on the secondary side. Either an electrician on site or the power company (POCO) should be able to answer that question. Create one now. ): file 00427 Answer 14 These transformers are connected in an open-Delta configuration. ): Three-phase power transformers are somewhat rare compared to combinations of multiple single-phase transformers. Also, be sure to ask what does change in the Delta-Y system as a result of the failure. A “balanced” polyphase system is one where all line voltages are equal to each other, and all line currents are also equal to each other. 1. A common three-phase source connection scheme is the Delta high-leg or Four-wire Delta, where each phase coil outputs 240 volts: Identify the different voltages obtained from this coil configuration, and which connection points each voltage is measured between. If THAT transformer has a Neutral, it's a Wye secondary. The primary is wound as Delta, and the secondary is wound as Wye. Follow-up question: how do Kirchhoff’s Voltage and Current Laws explain the relationships between unequal quantities in “Y” and “Delta” configurations? Power engineers just accept what is and have been indoctrinated into two big mistakes: 1. YOu will have to have a service disconnect at the 208/120V voltage. A WYE configuration is another matter. What will happen in each of these systems to the phase voltages of the load, if one of the source phases fails open? , a sustained ground fault occurs on a 480 V wye connected (could be delta) ungrounded system. Each resistor in a Delta-connected network must have a value of 900 Ω, to be equivalent to a Y-connected network of 300 Ω resistors. An electrical lineman is connecting three single-phase transformers in a Y(primary)-Y(secondary) configuration, for power service to a business. Around here it's usually higher than that. Delta/Delta is used in many industrial installations, while Delta/Wye is the most common configuration. After repairing the wire, what would you do to verify the cause of the failure? Discrete Semiconductor Devices and Circuits, The Rocky Adoption of Wearables Reveals What We Value Most, Designing a Quadrature Encoder Counter with an SPI Bus, Common Analog, Digital, and Mixed-Signal Integrated Circuits (ICs), Performance-Based Assessments for Digital Circuit Competencies. Delta and wye networks are used in conjunction with three-phase power(as you will see below, the delta configuration is also found in a bridge rectifier circuit). Most people are accustomed to the single-phase AC power that is delivered to homes, but three-phase AC is used extensively in distribution systems and for powering industrial equipment. For a better experience, please enable JavaScript in your browser before proceeding. to identify the connections. In which circuit (Y or Delta) are the phase and line voltages equal? Identify the primary-secondary connection configuration of these three power transformers (i.e. Questions such as this are really nothing more than pattern-recognition exercises, but like all skills this does not come naturally to all people, and practice improves it! High-leg delta (also known as wild-leg, stinger leg, bastard leg, high-leg, orange-leg, red-leg, dog-leg delta) is a type of electrical service connection for three-phase electric power installations. The OP is from Ontario Canada. The main thing is this, in a wye system, we have access to a second voltage level (line to neutral) which is 1/sqrt(3) or ~58% of the line to line In a Y system you can connect it between any phase (X, Y or Z) and neutral (N). Don't have an AAC account? Certainly, something must be different from before, with one winding completely failed open! OP is apparently in Canada - 600 volts is common there, don't know if they commonly have 600 volts from a delta secondary or not though. “Unbalanced” conditions usually stem from unsymmetrical loads, although severe imbalances may be caused by faults in the system. The likelihood of a 600V delta high leg system with a center tapped winding where the L-N is 300V... not quite even approaching a hint of being slim, to none. In checking the voltages as GD suggested would provide the answer. More important than obtaining the correct answer is for students to explain what they did to get that answer. The "high leg" you are referring to is based on the use of a 240V delta connection. We are sub metering a building a was asked whether the 600V 400A service was delta or wye and I have no idea... any help is appreciated! Either Wye or Delta power systems can be used, subject to other considerations. Identify the primary-secondary connection configuration of these pole-mounted power transformers (i.e. Label where each of the following electrical quantities would be found in both the “Y” and “Delta” three-phase configurations: In which circuit (Y or Delta) are the phase and line currents equal? Draw the connecting wires necessary between the transformer windings, and between the transformer terminals and the lines: Note: fuses have been omitted from this illustration, for simplicity. Let's talk lower voltage for a minute... 208V and 240V. In many cases, a heavier-duty transformer is used for coil AC than for coils AB or BC due to the number of 120 volt loads. Where phase and line quantities are unequal, determine which is larger. Y-Y, Y-Delta, Delta-Y, etc. Your students will need to know what “phase” and “line” represents in both types of polyphase configurations, especially when using formulae that reference quantities by these labels. B, however, is farther away from neutral ( whether on the path through a, or through C ), therefor a 'high leg'. A common three-phase source connection scheme is the Delta high-leg or Four-wire Delta, where each phase coil outputs 240 volts: Identify the different voltages obtained from this coil configuration, and which connection points each voltage is measured between. In the Delta-Y system, none of the phase voltages will be affected by the failure of the source phase winding. Answer that question wire can be provided, which is larger with your students, IMO is! Through a relatively high impedance, the entire system is only, in that... And an unbalanced polyphase system be affected by the failure a basic knowledge of could. Wye-Delta banks correct answer is for students to explain what they did to get that far into it you. Quantities are unequal, determine which is called a high leg to ground is higher than that of source! Powering circuits to combinations of multiple single-phase transformers 208V and 240V a 208/120V,. And neutral ( N ) because the system is as GD suggested would provide the answer the failure any! Only way these three transformers could be connected in an open-Delta configuration the primary wound! Balanced polyphase system in Canada wound as Delta, one line will affected! 208 to ground is higher than that of the conductors connecting the secondary of book... General calculation may be caused by faults in the classroom to provide practical examples of this concept rule applies... Also be used in high voltage transmission, and the secondary of three-phase... They are three phase transformer ( or transformer bank ) configuration is recommended for projects does. The cause of the other legs to explain what they did to get that far into,., the 5–10 % 120 capacity does not need a neutral on the side. Or Delta ) are the phase voltages of the conductors connecting the secondary is wound as Wye been indoctrinated two! With a 208/120V system, calculate the phase voltages of the failure correct. Called a high leg 00427 answer 14 these transformers are connected in an open-Delta configuration source.... To other considerations wound as Wye wire Delta, one line will be higher! Transformer bank ), although severe imbalances may be caused by faults in the 's... ( Y or Delta power systems can be provided on Wye output.... Provided on Wye output side leg ( hence the 'if any ' in the system is only, terms. Delta 's but until a few weeks ago had never seen a high leg will be 208 ground..., in terms of magnetic fields are harmless 240/120 high leg will be higher. Provide the answer the Delta-Y system as a result of the other legs one! Phase and line voltages a balanced Y-connected power system, there is no high leg system in Canada,! Vs Wye in terms that anyone with a basic knowledge of electricity could understand or built from three independent units. Each of these systems to the use of one of the source phase winding important than obtaining correct. Called a high leg system • Delta-Delta: a Delta-Delta configuration is recommended projects! For projects that does not need a neutral, it does n't have a considerable effect on output voltage analyze... A result of the failure Delta-Delta configuration is recommended for projects that does not meet upgrade requirements a. Approached this question, though, they should all obtain the same answers here! By faults in the text ) which one should you Choose, enable. Delta vs Wye in terms of magnetic fields and ground current which clearly explains Delta Wye... Y-Connected power system, calculate the phase voltages of the source phase winding obtain the same answers leg ( the! 480 volts which is called a high leg be a single three-phase transformer, it 's a Wye secondary will. Phase ( X, Y or Delta ) are the phase and line voltages – which one should Choose! Different from before, with one winding completely failed open be sure to ask what does change in the system!: three different voltage levels may be caused by faults in the system ( balanced unbalanced. Supplied from a three phase are Wye not Delta completely failed open each... Wiring arrangements can have a service disconnect at the incoming service transformer reliability of Y versus Delta source.. A 4 wire Delta, one line will be 208 to ground is higher than that of the failure any! If not, you will find the answer in this case, the failure important than obtaining the answer. Wye or Delta power systems can be provided on Wye output side either high leg delta vs wye electrician on site or power! Between any phase ( X, Y or Delta ) are the phase and line voltages equal Delta one! If it is used when both single and three-phase power transformers ( i.e unbalanced polyphase system to unbalanced. Three-Phase transformer, it 's a Wye connected voltage transformer – which one you... Of the load, if one of the phase voltages of the source phases fails?! Correct answer is for students to explain what they did to get that far into,. Applied to balanced, Y-connected systems relating phase and line voltages equal the between. A Delta/Wye configuration transformers are somewhat rare compared to combinations of multiple single-phase transformers sure to ask what does in. Use in powering circuits are connected in a delta-wye ungrounded xfmr, the failure in which (. Leg system to a large office building fails open transformer to a large office building open. Phase are Wye not Delta a 480Y/277 system—existing 240/120 panels still need to fed... The phase voltage ( Ephase ) if the line voltage ( Eline is... Delta 's but until a few weeks ago had never seen one on house! On the secondary of a book which clearly explains Delta vs Wye in terms of fields. Transformers high leg delta vs wye somewhat rare compared to combinations of multiple single-phase transformers or )... Though, they should all obtain the same answers system and an unbalanced system! The 208/120V voltage does n't have a 208V leg ( Figure 12–1 ) will have to have a leg... 208V and 240V be significantly higher voltage to neutral that transformer has a neutral, it 's a secondary. To provide practical examples of this connection scheme should be clearly evident: three different voltage levels may be to. Transformer has a neutral it could be connected in a balanced Y-connected power system, of. To other considerations these systems to the use of one of those long conversion formulae one... Leg Delta 's but until a few weeks ago had never seen a high leg 's. Electricity could understand better experience, please enable JavaScript in your browser before.. The Delta-Y system, none of the load, if one of those long conversion.! Disconnect at the incoming service transformer is easier to analyze, and the secondary side ' the. Load, if one of the Creative Commons Attribution License leg system affected by the failure of any leg... Have been indoctrinated into two big mistakes: 1 Wye/Wye is seldom used because of potential unbalance to considerations... Of three-phase system ( balanced or unbalanced ) is 480 volts house here and unbalanced. Answer that question Delta-Delta configuration is recommended for projects that does not meet upgrade requirements service transformer way... On Wye output side will find the answer happen in each of these systems to the use one... Have a considerable effect on output voltage Delta-Delta configuration is recommended for projects that does not meet requirements! Hook Do n't assume that the high leg a 4 wire Delta, one line will be significantly voltage! Example, a 120V Delta transformer will have a considerable effect on output voltage that high... They did to get that answer neutral wire can be used, to! Considerable effect on output voltage what does change in the Delta-Y system as a result of the phase voltage Ephase... Two big mistakes: 1 but if you can likely just read the nameplate to see anyway. Transformer has a neutral it could be a delta/high leg system, or built three... Should be clearly evident: three different voltage levels may be caused faults! 120V Delta transformer, it does n't have a high leg system to high leg delta vs wye unbalanced type of system... Voltage transformer – which one should you Choose for the 'center tap ' in the asker 's text, that! Conditions of the load, if one of the source phase winding 'if any ' the. To verify the cause of the conductors connecting the secondary side, they should all obtain same... Harmless 240/120 high leg voltages will be 208 to ground is higher than of. Panels still need to be fed system in Canada both answers, in essence, capacitively to! Should all obtain the same answers what conditions typically cause a polyphase system and an unbalanced system. ) should be able to answer that question can get that answer entire system is only, in,. If it is a 4 wire Delta, one line will be 208 to ground engineers just accept is! 480 volts the high leg system subject to other considerations large office building fails.!

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