Trust is hard to come by in St. I-Line) often require special breakers for 240V which are built using 3-pole housings. Northern Virginia. That corner grounded delta system still needs equipment grounding conductors run beyond the service disconnecting means, you do not bond any equipment to the current carrying B phase at equipment you run separate EGC like you do for other voltage systems. 6. If an electrical system is grounded as a requirement or by choice, all the rules related to grounded systems must be applied. And, without proper identification of the. Corner grounded delta. M. We didn't add a transfer switch however; but there were existing generators and transfer switches present that were much newer than the existing electrical service. Therefore, many historic structures still have operating delta-delta service transformers where one corner of the transformer has been grounded to provide 120 V/240 V power within the facility. ”The VFD that I have now is an older model Woods E-trac X2C-40150 and the manual does not say anything about corner grounded delta. I would call the 4rth wire a ground wire unless it was used for load unbalance. When you look up Conductors, then Grounded you will find the first reference given is Alternating current systems, 250. A high-leg system is a hybrid between a standard 3-wire single phase and a 3-phase system. The minimum size of the grounded conductor for a 3-phase, 3-wire, corner-grounded, delta connected service is a. Some devices will have multiple interrupting ratings, such as 14,000 amperes at 600 volts and 25,000 amperes at 480 volts. Eaton Corporation literature states “for all 3 phase delta grounded B phase applications, refer to Eaton Corporation. We're working in an old mine machine factory, recently converted to a gear shop. A straight rated CB (such as 480V) can be applied on systems that have no more than 480V between any two conductors. I figured at the least it would cause a phase loss alarm, but wasn't sure if there. 24 I see 250. Grounded B-Phase Systems (Corner-Grounded Delta) PowerPacT B Electrical Accessory Wiring Diagrams. Schneider Electric has tested equipment for use on corner-grounded delta systems to provide Underwriters Laboratories Inc. C orner-grounded delta grids are not supported at these voltages. Electrically, the grounded conductor in a corner-grounded delta system operates identically to a multi-grounded neutral conductor on a wye system meeting Rule 230E1. For safety reasons the tank would need to be grounded, and for symmetry reasons it would need to be a neutral. joethemechanic. LHL361005861). 4. This is a "Corner Grounded Delta" system and is found in older facilities that have no need for 277 volt service such as a manufacturing facility or a central plant in an apartment complex. If you have a 3-phase motor on a center-tap system, the grounded conductor does not come into the picture at all. You're describing "high leg" or "wild leg" delta. You can run a typical two-wire line-to-line load off just a single pole breaker because on this. - All phase L-L voltages are normal and the same. –See Figure 4. Joined Jan 25, 2011. I believe that you are not supposed to connect any single phase loads between the high leg and the neutral. The other two phased are at the line voltage above ground. There are certain restrictions when using a VFD on a corner grounded delta power system. Re: Ground Fault Protection in Corner Grounded Delta System. This question references Article 240. For starters the xformer 480 side, if grounded, all the load side gear and equipment must be approved for corner grounding-not likely. I wasn't sure what issues it might cause having one of the phases to ground be 0 volts. Commercial buildings require 3P4W and ground. Section 250. Introduction Corner-grounded delta systems are not re commended for new installations. Now connect one corner of the triangle to ground. if a guy happens to pick the corner-grounded leg to test to ground to verify that the line is off, then there is the potential for mayhem. I was planning on reverse feeding it with 208v, and getting 480v. Jul 26, 2017. Not sure what you mean by “normal”. Another disadvantage, as given on page 33 of IEEE Std 142. PowerPacT B-Frame Let-Through Energy Curve. a delta winding, with the corner ground not causing any difference to actual operation unless the higher voltage from tap to ground is a specification issue, or. 8. We have addressed neutral loads using individual 480V x 480/277V. Hi, Our company rented an old warehouse and this is the first time I've ever seen corner ground delta (CGD) panel. 480V. Corner grounded delta systems are good in theory, but only with older types of loads. ain't going to end well. The grounded conductor is treated like a neutral in 120 V and 240 V single-phase systems. 12. Menu. Corner-grounded delta system. The other two will be 240v to ground. the panel has two bus bars and grounded bar. Jun 21, 2023. Subsection 250. At the transformer, the grounding electrode conductor, grounded phase, and equipment grounding conductor all tie together. i agree. A new transformer was set for a motor load to step up to 480 volt. An ungrounded (floating) delta should have a ground indicator to alert maintenance personnel because a second ground may be catastrophic. corner grounded delta service. The NEC® addresses slash voltage ratings for circuit breakers in 240. In most cases a corner grounded delta is a very poor choice of supply as it has a. , the neutral point of a wye-connected transformer and the phase on a corner-grounded delta connection. There is no way of grounding a 480V system (or any over 260V L-L) to meet the 150V L-G standard. Aside from serving the step-down transformer, the 480V side is mostly going unused. 20 informational not refers to a corner grounded delta tranformer. 277V. 5. ) Only standard ampere rated fuses and circuit breakers found in 240. Could be the outlet is miswired or mis-breakered and has two of one line and one of a second. rbulsara (Electrical) 16 Jun 05 20:28. One line conductor is grounded (conventionally it is BØ). ) A 480/277-volt, 3-pole circuit breaker can be applied on a 480-volt corner-grounded delta. 6. 61 (A) Exception has a requirement for a 140% factor for calculating the neutral load from the unbalanced load on a 2-phase feeder. Sounds like you know you have three supply conductors but don't exactly know what they are. To obtain UL certification, the TVSS unit must pass all tests. Might be more economical to just order 240V equipment and use whats there. A two-pole circuit breaker applied on a 3-phase, corner-grounded delta system must be marked 1Φ-3Φ. 220. Furthermore, 3-phase, corner-grounded, delta circuits can only use two-pole circuit. Trying to determine if I have a ground fault somewhere or a bad leg or breaker. D. Location Michigan Occupation Electrician Feb 24, 2023 #4 This is a 4 wire 3 phase delta high leg system. A two-pole circuit breaker shall not be used for protecting a 3-phase, corner-grounded delta circuit unless the circuit breaker is marked 1f- 3fto indicate such suitability. 120V. T. Per NEC, not for use with ungrounded systems, impedance grounded systems or corner grounded systems (com-monly known as Three Phase Three Wire Delta, Three Phase High Leg Delta and Three Phase Corner Grounded Delta systems). The current flowing in each circuit conductor to the load is ___ amps. The manufacturing plant that I worked for always bonded the X0 of a 480v delta -208y/120 to the frame but as I understand it not all manufactures do this I picked up upon when using one as a step up transformer. Start shipping your package by locating a Purolator drop box, Purolator Shipping Centre, or Purolator Authorized Shipping Agent near you. 480 V, 3-phase, 3 W, ungrounded or high resistance grounded VII. It then goes on to discuss performing an open corner test to ensure proper polarity when c. High leg deltaGrounded solidly system delta ground wye electrical fault engineering phase grounding systems portal circuit overview short Corner-grounded delta (grounded b phase) systems data bulletinGrounded b phase. 60% of these I run across are done incorrectly. The "wild leg" has a different voltage to ground, which can. Phase ab 240v, ac 240v, bc 240v, a to ground 120v, b to ground 0v, c to ground 120v. not smaller than the required grounding electrode Corner grounded Delta. J. You are now operating on a corner grounded delta unintentionally. The Article 100 definition for neutral was added in the 2008 NEC. A circuit breaker with a slash rating, such as 120/240 V or 480Y/277 V, may only be installed in a circuit where the nominal voltage of any conductor to ground does not. If you choose the corner grounded delta, you will lose your three phase power that you need. The delta system has a phase-to-phase voltage of 240 V. Indication Contacts. Home. Wye-wyes are extremely rare in <600V systems. This is a 277/480 volt system. 'power' panels (e. 86 restricting their use to solidly grounded systems where the line to ground voltage does not exceed the lower of the two values and the line voltage does not exceed the higher value. domnic Senior Member. Hi, Our company rented an old warehouse and this is the first time I've ever seen corner ground delta (CGD) panel. If the leg chosen is the B phase, then the voltage to ground for A and C will be 240 volts, while for B it will be zero. False. Is the power system 3 phase, 3-wire or 4-wire? If only the three phase conductors are being brought to the MCC, the power system is a 3-wire system. A corner-grounded delta transformer connection is an example of a system permitted to be grounded. Fig. B phase is bonded to ground at the transformer lugs, not in the switchgear. 5869 posts · Joined 2009. teal854t Discussion starter · Oct 13, 2010. Schneider Electric has tested equipment for use on corner-grounded delta systems to provide Underwriters Laboratories Inc. It is a 240v CGD. High leg delta has the mid point of one side. NEC Article 100 defines interrupting rating as “The highest current at rated voltage that a device is intended to interrupt under standard test conditions. As far as marking, I have never seen a corner grounded system where the grounded conductor was identified as required by the rules in 200. The uncommon grounded system is a 3-phase, 3-wire corner-grounded delta system. I guess what I'm saying is that Delta seems never to be a good option. From there a grounded phase conductor and equipment ground go to the disconnect and remain separate. A 3-phase disconnect or overcurrent device shall not be connected to the bus of any panelboard that has less than 3-phase buses. three-phase, 3-wire, corner-grounded delta system? 120V 240V 277V 480V Correct Answer: 480V. Doing this is technically challenging and expensive, however, the corner-grounded system offers. might occur when Phase A goes to ground on a 480V, B-phase, corner grounded delta system. You will measure 480 volts from either A phase or C phase to ground, B phase to ground will measure 0 volts. Occupation. The two pole breakers can handle 240V or more to ground, as would be seen in a 416Y/240 system or a 240/480 three wire single phase or a corner grounded 240 delta, but not the 480V to ground seen in a corner grounded delta. The motors operate at a nominal supply voltage of 220 volts, 3 phase. The maximum continuous operating voltage is measured from phase to phase for impedance grounded and ungrounded systems. You only need two current transformers to monitor the power in a 3 phase, 3 wire system. It would seem to me, that there is no difference in principle between the grounded conductor in a 3 phase, 4 wire delta system, the grounded conductor in a 3 phase, 4 wire Y system, or the grounded conductor of of a 3 wire 240/120 volt system, or the grounded corner of a delta system as being disscussed. Other 2 phases = line voltage. You must also bond the phase to the case with a jumper sized to 250. Two ways to use the Grounded Conductor on 3Ph 3W Delta Two ways to use the Grounded Conductor on 3Ph 3W Delta Check out these Schematics, regarding a 3 Phase 3 Wire Corner-Grounded Delta, and the Two ways the. Grounding is important as it provides a current path back to the source should an ungrounded conductor fault to ground. It could also prohibit a corner grounded 240V delta since using a grounding transformer a 240V system could be grounded with a L-G voltage of only 139V. The CB panel fed by the transformer secondary (240/120V) has a grounding electrode where the secondary center tap (neutral) is connected but as stated the corner grounded delta supply is not connected to it. NEC expert Mike Holt explains how to properly ground a corner grounded delta system and the special characteristics of these rare systems. Does service entrance equipment still have to have neutral bus in this case? Steve. 2 requires a grounded conductor in all premises wiring. This includes the rules in 230. corner grounded delta systems, considers the circuit breakers’ individual pole interrupting capability. It could also prohibit a corner grounded 240V delta since using a grounding transformer a 240V system could be grounded with a L-G voltage of only 139V. . See Figure 11. - One phase is intentionally grounded. 26(4) and 250. Typically in my area BOY is used for any 480 volt power and if a grounded conductor involved, it is grey or marked grey. Always wear your gloves. Grounding B phase is standard when working with older. Such a system changes to a corner. It is a 240v CGD. not smaller than the size of the grounding electrode. If A to B = 240, B to C = 240, and B is grounded, then A to ground and C to ground is the same potential as A to B or B to C. . Think about this a little more. 24(D)(4) This section covers impedance grounded services. NEC 240. He has tied the grounded phase of the delta supply to the green. It is also known as red leg connection or wild leg connection or orange leg connection. The other two phased are at the line voltage above ground. Cause what is happening then is the 3ph load is seeing A,C,A or C,A,C. Use of a slash rated breaker on a corner grounded delta is not ruled out by it not being solidly grounded but by the voltage to ground on the two ungrounded wires being greater than the second number in the rating. This system has multiple transformers that go from 480-208 delta-delta and also 480v delta-208/120v wye. - One phase is intentionally grounded. When connected to the no. That is a corner-grounded delta system. If a phase opens, that is still a phase loss. 5 . 415V. . Thread starter William Robertson; Start date Jan 21, 2021; Status Not open for further replies. It's 830 wye. A high leg delta connection is a configuration in which one of the windings in a delta connected secondary of a transformer is centre-tapped and grounded. 796v is what's marked on a motor used on these 830 systems. The correct solution is to use a 208 Delta X 480Y xformer. This video is based on the 2020 NEC and was extracted. They have 3 phase delta 480. Corner grounded delta systems are common in old industrial facilities around St. a Split Phase circuit with 120V from each respective leg to Neutral (residential power tap - grin). For use on 480 V systems, LH type circuit breakers must be ordered as 600 V versions and with a 5861 suffiix (i. 67 to 1. This question references Article 240. (2) A circuit breaker with a slash rating, such as 120/240 V or 480Y/277 V, shall only be installed in a circuit where the nominal voltage of any conductor to ground does. Furthermore, 3-phase, corner-grounded, delta circuits can only use two-pole circuit breakers marked 1ɸ-3ɸ. 26. I have multiple 240v single phase loads and (1) 240v 3 phase load. He said that it's about 240 volts so 128 volts to ground isn't that far off for a corner grounded Delta. In a delta configuration, the three windings are connected end-to-end to form a closed path. Its hard to visualize attaching 1 of 3 energized lines to ground. I partially agree. This supply system configuration is often used where high power is required, for example for large mo-tors. The Delta system has aThe NEC requires EITHER that a delta system be corner grounded OR you must have a "ground monitoring system" in place. The cost of running a neutral to the service disconnect seems like a cheap way to save expensive headaches. Corner grounded Delta transformer systems are known to confuse people. I got a call today from dry cleaners he wants to add new washer. NEC 430. Not sure why you would see a voltage increase if you lost a primary phase, though. The leg that reads zero to ground is the grounded leg. ChrisSeems like a trick question. When solving for phase current, don’t forget to divide the overall transformer kVA rating by 3. Thus, the phase which is corner grounded has zero volts relative to ground because we have chosen to bond it. The grounded leg of a corner grounded delta simply cannot be the 'same' as the grounded conductor of a center-tap delta. It consists of a maximum current and the voltage at which the device is rated to interrupt the circuit. 1. 240V. Not sure what you mean by “normal”. We did an upgrade at a plant that had a corner grounded delta service. ) 480 3ø, 3W Wye connected Impedance grounded system. For NEMA Type 4X Fiberglass Reinforced Polyester switches, see Fiberglass Reinforced Polyester Enclosures—NEMA 4X. At first we were having trouble getting the motor to start in auto and just out of habit I checked power in. When the bond is made from B phase to ground, you are simply creating a reference point. Question I have is I believe I need to utilize a corner grounded delta on the 480v side, otherwise the system is not grounded. It is both, ground and hot. Corner-grounded delta. A straight rated CB (such as 480V) can be applied on systems that have no more than 480V between any two conductors. 208, 240 and 480 are all common 3 phase systems. A circuit breaker with a slash rating, such as 120/240V or 480Y/277, shall be permitted to be applied in a solidly grounded circuit where the nominal voltage of any conductor to ground does not exceed theThe system is “corner grounded”, one leg of three phase delta is tied to ground. If such systems are grounded, they shall comply with the applicable provisions of this article. Corner-Grounded Delta Circuits. This can be avoided by simply checking more than one leg, but the plain fact is that the customer doesn't like corner-grounded delta, and doesn't want it used. I know each leg has 240v to another phase or to ground except for the "B" phase so its not like the. e. A 480 Δ — 240-volt 3-wire Δ transformer is delivering power to a 3Ø load and has 75 amps of coil current flowing through each winding. Also note the one can use a slash rated breaker on a corner grounded 240 delta, it just has to be a 480/277 rated breaker. For alarm switch, add the suffix BA. This is a non sequitur. Rick It is both, ground and hot. Not a corner grounded delta. For me, its a textbook corner grounded delta. ppsh41pro • 10 mo. This section classifies the systems that must be grounded – unless prohibited elsewhere in the Code – into four categories. ” Following are sketches of what the voltage source looks like with a breaker applied. We use our. 120 V, 3-phase, corner-grounded delta. scriverman. Figure 4 – Fault to Ground on a Corner-Grounded Delta System A disadvantage of Corner-Grounded Delta systems is the inability to readily supply voltage levels for fluorescent or HID lighting (277V). No magic and no mysteries. 61 (A) Exception has a requirement for a 140% factor for calculating the neutral load from the unbalanced load on a 2-phase feeder. Grouch1980 said: Actually I didn't specify it. D. However, some utilities still provide this system, and many old installations still exist. Either they should have been protected by the circuit, OR they should have been a self-protected type. Schneider Electric has tested equipment for use on corner-grounded delta systems to provide Underwriters Laboratories Inc. About us. Feb 3, 2009. Ground B phase systems, grounded phase services, and end-grounded delta systems are all examples of corner-grounded delta systems. Corner-grounded Delta One line conductor is grounded directly. I have a job where they want to install a Dan Foss FC202 on a pump. 362K subscribers in the electricians community. 2778 posts · Joined 2014. ) Branch-circuit fuses do not have to be marked with their ampere rating. 3, July 2022 -Corner-grounded delta grids not supported at voltages of 400V / 480V Version 1. A corner grounded delta is not ungrounded. looking for advice on working on a 3 ph, 3 wire 480 delta that i believe fits the definition of a corner grounded delta. Check Details. A 120 V, 3-phase, 3-wire delta requires the grounding of one of the corners to comply with NEC 250. A corner grounded delta power system is a configuration where one of the phases (typically B phase) is solidly grounded. Grounded Systems Ltd Company Profile | Victoria, BC, Canada | Competitors, Financials & Contacts - Dun & BradstreetHotel Pulitzer, Amsterdam; L’Hermitage Vancouver, BC; Four Season Nevis, BVI; Rosewood Miramar Montecito, CA; Residences at Little Nell Aspen, CO; St Regis Bal. 2 requires a grounded conductor in all premises wiring. A-B: 240V. (2) In ungrounded systems, impedance grounded systems, or corner-grounded delta systems unless listed specifically for use on these systems. #3. “A circuit breaker with a slash rating, such as 120/240V or 480Y/277V, shall be permitted to be applied in a solidly grounded circuit where the nominal voltage of any. 277V lighting is designed for a grounded system where the connection is to a hot and a neutral. The neutral is by definition a grounded conductor but if you had a corner grounded delta system the grounded conductor would not be a neutral. My question is on the secondary side I need to take a bonding conductor from any of the three phase to ground to created a corner grounded delta, I know I've done a set up like this in the past but grounding a phase always makes me. Also be aware that your gear will have to be listed for use with corner grounded delta and some loads are not acceptable for use on a corner grounded supply. What we have is 4160V feeding 4 step down transformers that step it down to 230V Grounded B. Is the transformer output an ungrounded or corner grounded delta? If ungrounded, a ground detector must be provided. ® (UL®) Listed products for this application. Ground fault sensing is undefined for the grounded phase, so typically cannot be used at locations where ground faults are required, such as healthcare facilities. - All phase L-L voltages are normal and the same. (UL®) listed products for this application. 20(B)(1) and avoid an NEC violation. The inverters may not like the elevated voltages to ground. One-line diagram symbol for a corner-grounded delta transformer _____ l. Apparently, code requires this conductor to be phased white or gray but many People outside of code apply alternate color tape to the conductor because this is also a. If such systems are grounded, they shall comply with the applicable provisions of this article. At the risk of repeating myself, I'll try to illustrate the difference with a few examples. #1. This configuration goes by several names including grounded. Z. As the project is presently designed, we are stepping this down to 208/120Y and serving all of the building's loads via the 208/120V distribution system. In my experience, there always seems to be a higher current on the. 22, 2005 nec. Listed means one follow the instructions. For starters the xformer 480 side, if grounded, all the load side gear and equipment must be approved for corner grounding-not likely. There is no 120 or 277 volt lead, you will need to. Not open for further replies. They based it on current measurements they took at the pole after checking and cleaning all connections. System grounding is the connection to the ground – solidly or through impedance – of current-carrying conductors – e. However, some utilities still provide this system, and many old installations still exist. Aug 14, 2018. A corner grounded delta service can be designed for any desired voltage, but 240 is most common. Not open for further replies. True. One method of grounding a three-phase, three-wire, delta-connected system is to ground one of the phase conductors. If the available line-to-ground fault current exceeds 8,660 amps at 480 volts, such as might occur on the secondary of a 1000 KVA, 480 volt, corner-grounded delta transformer, the circuit breaker may be misapplied. ® (UL®) Listed products for this application. Yes, that is my understanding too. BUT you have a 2 to 1 transformer (480/240=2 to 1) at 208 in you would get 416 out. This video covers voltage relationship for a Delta source or load. 3 pole breakers may also be used for single phase loads which will be connected through the outside poles. 13. On BOLTED faults the first fault to ground turns it into a corner grounded delta system but doesn’t trip anything. T. Other types of three-phase supplies are wye connections, ungrounded delta connections, or corner-grounded delta ("ghost" leg configuration) connections. Aside from serving the step-down transformer, the 480V side is mostly going unused. #4 · Oct 2, 2020. MRG, Article 200. We use our trainer model made by Three Phase Innovations to. This supply system configuration is often used where high powers are required, for example for large motors. If you had a corner grounded delta, B phase grounded and A phase shorts assuming you protected everything per the NEC you would have a ground fault and the fuses would blow or the CB open. Location DFW, Texas. A phase is connected to each corner of the delta. , a zero sequence voltage). If corner grounded delta system, use outer switching poles for ungrounded conductors. 61, 517. #4. Schneider Electric has tested equipment for use on corner-grounded delta systems to provide Underwriters Laboratories Inc. Basic cheap plug-in breakers are “slash” rated, meaning 240/120V; they are rated 240V phase to phase, but 120V phase to ground. True False. Directions Advertisement. There are circuits where grounding is prohibited. You will read 480v from l1 and l2 to ground, 0 v on the neutral leg to ground. Delta wye transformer wiring arrangementDelta wiring diagram 4 wire 240 volt wiring diagramDelta phase system wiring wire three grounded corner. This wire must be white or grey, because it is a grounded conductor, even though it isn’t a neutral. Proper grounding reduces overvoltages, improves uptime, and isolates faults. 600 Y/347 V, 3. The 277 volt is interesting but, not relevant. 20(A). The correct application is 480 V or 600 V straight voltage ratings. One phase center tapped to derive a different voltage. 8kv/480V Y transformer. That is the key answer with open delta system and I know it is common used on some resdentail and a bit of small commercal location. Frame size EMC filter (+E200) screw Ground-to-phase varistor screw R10,. Not available with HA option. is located/eliminated asap. L-G phase readings are L-L V. The size of the step-down transformer is. That’s why you get 0volts from it to ground because it’s at the same potential. A diagram of such a system is shown at __ in figure 304. It is found that, although this type of service is less expensive than solidly grounded wye service, 480 V corner-grounded delta service may not provide a safe working environment if used for oil-field service. Just speculation: Probably not really a neutral, but they likely had one leg of the delta winding grounded (corner grounded delta) because if not, they would have needed to add ground fault monitoring to that circuit, and at 4160V, that would have been expensive. Our instructor made a point to warn of corner grounded Delta transformers, since you get your "phase-to-phase" voltage present "phase-to-ground". Could be as jraef mentioned. Although delta windings are often operated ungrounded, a leg of the delta can be center tapped and grounded, or a corner of the delta can be grounded. The earth. When the bond is made from B phase to ground, you are simply creating a reference point. Phase readings as follows: A to…By grounding a corner of the delta, you help stabilize the phase to ground voltages and the phase to phase voltages will also be stable. Kettle's on. 230 is also a 3 phase system voltage that comes in a couple of different flavors: Corner grounded Delta, or a mid point grounded Delta with the B phase bastard leg. Corner-Grounded Delta System. micromind · #7 · May 3, 2023. The utilty provider is coming in with 480 delta corner grounded c phase. This video is based. 4kV service right into the customers plant, where the customer has a transformer (in our company it's a 600kVA delta-delta) to decrease the voltage. Currently, the secondary of the transformer enters our switchgear which has a disconnect for each of the 2 sides of the switchgear. 3 Phase grounded delta three wire 480 volt to single phase 240/120 volt transformer to 200 amp panel , does the 480 volt grounded phase always come in. This is a diagram of a normal (North American Standard), delta primary, wye secondary, transformer. 240 V, 3-phase, 3 W, ungrounded or corner grounded delta V. Another indicator is you say your VFD’s run fine, the vast majority of VFD’s have MOV surge. Corner Grounded Delta Transformer Bank. Only for use with 480V Wye systems.