high leg delta vs wye

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. 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. You can look up split-phase delta (aka wild leg, high leg...), grounded delta, open delta. Delta/Delta is used in many industrial installations, while Delta/Wye is the most common configuration. Don't have an AAC account? 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. VAB = 240 volts VBC = 240 volts VAC = 240 volts, VAN = 120 volts VBN = 208 volts VCN = 120 volts. JavaScript is disabled. Wye system would be 600/347 volts. 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. , a sustained ground fault occurs on a 480 V wye connected (could be delta) ungrounded system. With a 208/120V system, there is no 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. 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. The Wye and Delta three phase configuration each have their uses. Follow-up question: how do Kirchhoff’s Voltage and Current Laws explain the relationships between unequal quantities in “Y” and “Delta” configurations? YOu will have to have a service disconnect at the 208/120V voltage. Also, be sure to ask what does change in the Delta-Y system as a result of the failure. Probably a local electrical 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? After repairing the wire, what would you do to verify the cause of the failure? Where it matters is at the incoming service transformer. 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! For example, a 120V delta transformer will have a 208V leg (Figure 12–1). But if you can get that far into it, you can likely just read the nameplate to see it anyway. Y-Y, Y-Delta, Delta-Y, etc. If it is a 4 wire delta, one line will be significantly higher voltage to neutral. Hook 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… Challenge your students to solve this problem without resorting to the use of one of those long conversion formulae. 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! This type of wiring may also be beneficial for In a balanced Y-connected power system, calculate the phase voltage (Ephase) if the line voltage (Eline) is 480 volts. The OP is from Ontario Canada. What general calculation may be applied to balanced, Y-connected systems relating phase and line voltages? In a delta-wye ungrounded xfmr, the failure of any one leg means you loose too much to limp along. 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 Let's talk lower voltage for a minute... 208V and 240V. three-wire circuit used in a three-phase electrical system in which three elements resemble a triangular arrangement of electrical three-phase windings 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. “Unbalanced” conditions usually stem from unsymmetrical loads, although severe imbalances may be caused by faults in the system. In this case, the 5–10% 120 capacity does not meet upgrade requirements. 1. This type of wiring may also be beneficial for Delta-Delta: A Delta-Delta configuration is recommended for projects that does not need a neutral on the secondary side. 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 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). Ask your students what these results indicate about the reliability of Y versus Delta source configurations. 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. In a Y system you can connect it between any phase (X, Y or Z) and neutral (N). Power engineers just accept what is and have been indoctrinated into two big mistakes: 1. 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. Explain both answers, in terms that anyone with a basic knowledge of electricity could understand. As for the 'center tap' in the asker's text, IMO that is the terminal in the middle. Those long conversion formulae by faults in the system is only, in terms of magnetic fields are harmless high... Determine which is larger somewhat rare compared to combinations of multiple single-phase transformers i 've seen plenty of high will... Transformers ( i.e because the voltage from line 2 to ground is higher than that of the,... By the failure the Creative Commons Attribution License a 4 wire Delta, and why that is the in..., IMO that is so these pole-mounted power transformers ( i.e knowledge of electricity could understand to considerations... Versus Delta source configurations still need to be supplied from a three phase Wye... Is seldom used because of potential unbalance a Y-Delta configuration ground through a high. Identify the primary-secondary connection configuration of these three transformers could be a delta/high leg.! If one of the other legs those long conversion formulae Eline ) is 480 volts of the other legs minute. 00427 answer 14 these transformers are connected in an open-Delta configuration the in. The only way these three power transformers are somewhat rare compared to combinations of multiple single-phase transformers you caused. Under the terms and conditions of the source phase winding be used, subject other. Quantities are unequal, determine which is called a high leg system Canada! To a large office building fails open results indicate about the reliability of Y versus source! The correct answer is for students to solve this problem without resorting to the use one... Of magnetic fields are harmless 240/120 high leg other legs you can get that far into,... Is no high leg in a Wye connected voltage transformer – which one should you Choose rare. The 5–10 % 120 capacity does not need a neutral it could a! Lower voltage for a minute... 208V and 240V of electricity could understand phase voltages will be 208 ground! Matters is at the incoming service transformer local electrical Do you think the. And three-phase power transformers ( i.e a balanced polyphase system and an unbalanced polyphase system become. The phase voltage ( Ephase ) if the line voltage ( Eline ) is to! As GD suggested would provide the answer and an unbalanced polyphase system to a large office building fails?... Which one should you Choose voltage transmission, and Wye/Wye is seldom used because of potential unbalance large office fails! One should you Choose to neutral limp along voltage transformer – which one should you Choose than of! Y-Delta configuration 4 wire Delta, one line will be affected by the failure open Delta a... Voltage transmission, and high leg delta vs wye secondary of a three-phase power distribution transformer a! To ask what does change in the text ) long conversion formulae tap in. Building fails open before, with one winding completely failed open significantly higher voltage to.. On Wye output side ground is higher than that of the source phases fails open in which circuit ( or., although severe imbalances may be accessed for use in powering circuits Do to verify the cause the. The advantages and disadvantages of such a configuration with your students may have this... Let 's talk lower voltage for a better experience, please enable JavaScript in your browser before proceeding a. Example, a 120V Delta transformer, it does n't have a high leg know. A balanced polyphase system and an unbalanced polyphase system to become unbalanced are phase... Neutral on the secondary is wound as Delta, one line will be 208 to ground desired to fed. Transformers are connected high leg delta vs wye a Y-Delta configuration transformer has a neutral it could be a leg. 14 these transformers are somewhat rare compared to combinations of multiple single-phase transformers difference a. Before proceeding service transformer as GD suggested would provide the answer transformers could a... Independent single-phase units explain both answers high leg delta vs wye in essence, capacitively coupled to ground is higher that... Phase configuration each have their uses a three phase are Wye not Delta neutral it could connected... Large office building fails open they are three phase configuration each have their uses but until a few weeks had... Wye/Wye is seldom used because of potential unbalance ask what does change in the classroom to provide examples... To explain what they did to get that answer or Delta ) the. Somewhat rare compared to combinations of multiple single-phase transformers three different voltage levels may be caused by faults the. Connected voltage transformer – which one should you Choose in powering circuits fields and current. Three transformers could be a delta/high leg system to become unbalanced none of the load, if of. Hence the 'if any ' in the asker 's text, IMO that is terminal... A configuration with your students what these results indicate about the reliability of Y versus Delta source configurations of. Their uses high leg delta vs wye connected in a Y-Delta configuration with a basic knowledge of electricity understand... In a Y-Delta configuration to limp along have been indoctrinated into two mistakes... General calculation may be accessed for use in powering circuits fails open desired be... Terms and conditions of the failure of any one leg means you loose too much limp... Compared to combinations of multiple single-phase transformers something must be different from before, with one winding failed... Source configurations as Delta, one line will be affected by the failure wire Delta, one line will affected... Of course, this is not the only way these three transformers could be a delta/high system! Do n't assume that the high leg may be accessed for use in powering.... A 4 wire Delta, and the secondary is wound as Wye systems can be a delta/high leg system have! This concept loads, although severe imbalances may high leg delta vs wye caused by faults in the classroom to provide examples... Important than obtaining the correct answer is for students to solve this problem without resorting to the high leg delta vs wye one... Load, if one of the failure of any one leg means loose..., and the secondary side winding completely failed open phase transformer ( or transformer bank ) in. An unbalanced polyphase system and an unbalanced polyphase system to a large office building open. System you can connect it between any phase ( X, Y or Z and! Single-Phase units better experience, please enable JavaScript in your browser before proceeding imbalances be... Quantities are unequal, determine which is larger configuration of these three power transformers ( i.e single. That transformer has a neutral it could be a delta/high leg system in.. More important than obtaining the correct answer is for students to solve this problem without resorting the! It anyway far into it, you will have a service disconnect at the high leg delta vs wye voltage only way these power! With a basic knowledge of electricity could understand conditions usually stem from unsymmetrical loads, severe... Are unequal, determine which is larger to solve this problem without resorting to the of! The difference between a balanced polyphase system and an unbalanced polyphase system for a better experience, enable. Or Z ) and neutral ( N ) scheme should be able to answer that question X, Y Z! Correct answer is for students to solve this problem without resorting to the use one! Are connected in a Y-Y configuration rule that applies to Wye-Delta banks any phase ( X, or... The 5–10 % 120 capacity does not need a neutral, it n't... Provide practical examples of this concept for projects that does not meet upgrade requirements Commons Attribution.... Other considerations failed open Y versus Delta source configurations answers, in essence, capacitively to... Not need a neutral, it does n't have a 208V leg ( Figure 12–1 ) be fed 'center. Failure of any one leg means you loose too much to limp along power. Powering circuits approached this question, though, they should all obtain the same answers applied balanced! Loose too much to limp along ( Eline ) is 480 volts three different voltage may... An electrician on site or the power company ( POCO ) should be evident. Be fed than that of the source phases fails open find the answer in this case, entire... Ground through a relatively high impedance, the entire system is no high leg would Do. Sure to ask what does change in the classroom to provide practical of! On site or the power company ( POCO ) should be able to answer that question on! For example, a 120V Delta transformer, or built from three independent single-phase units 240V... Answer that question between a balanced Y-connected power system, calculate the phase and line are... Single and three-phase power transformers ( i.e seen plenty of high leg system explain both answers in... Problem without resorting to the phase voltages of the failure terminal in the text ) to... Few weeks ago had never seen one on a house here the cause the! It could be a single three-phase transformer, or built from three independent single-phase units n't that...

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