3 phase lost leg. But it doesn't appear in the '71.

3 phase lost leg. I need a heat sink for each block.

3 phase lost leg So the typical trip point is set to 40% of the maximum current. com/store/apps/details?id=co. The mathematical power relationship is just the basic 1 phase vs 3 phase power because you have gone FROM 3 phase TO single phase. I checked the main lugs before the main breaker and confirmed my prediction. So, this issue needs to be addressed as early as possible. *In 3PH3W system configuration, if any two phases of V L-L falls below the pickup setpoint setting and remain there long enough to satisfy the pickup time delay period, the phase loss alarm is triggered. Burned Windings: Excess heat may melt insulation and damage windings. Go back to Contents Table ↑. Phase to After doing some reading, it sounds like if a phase is lost on a delta-side of a transformer that other two legs will still energize the lost leg and, assuming the windings are beefy enough to handle it, the wye-side may not necessarily see any change. In a 3 phase electrical application, if you observe the electrical disconnect box or the electrical panel of the HVAC unit, you will find three power legs and one ground leg feeding the HVAC unit. Several of these loads may be 120/240 single phase. If you bypass the grounded leg switch, and then later someone accidently cuts or ignorantly removes the ground from the transformer, suddenly there is live unswitched 480 volts on the slugged leg. draw on any leg should have been 19. We once lost a fuse on one of the power busses and the area ran fine until all the machines shut down for the weekend. kamenges Member. It should not be 220 to ground. Also, in response to some other comments, it is not a short circuit so don't go looking for that. of 3 phase During phase loss, a 3-phase motor can regenerate more than 92% of the supply voltage in the open phase. The manufactured leg will be about 90 opposed and should measure about 240 to the other two legs and about 180 something to ground. If you measure the voltage between phase and phase you get 480V. There are 3 other transformers connected to the The "how can it start" issue is what GD said about OTHER loads running at the same time (on the SAME circuit by the way), or the loss not being complete on the missing Phase loss can be caused by a broken power line, a lightning strike, an open supply transformer winding, a mechanical failure in switching equipment, or when a single fuse A single-phase event occurs when one leg of a three-phase system is disconnected or otherwise lost. I found that they only used the high leg on their 3 pole breakers, there were mostly 2 pole breakers and they skipped all the high legs. The #1 phase is at 1. My questions is, can I run just one leg of 3 phase with a generator? Right now I have a giant generator running the whole panel. It was a 15hp 480V motor with a mag starter and no drive. one fuse opens" did you mean lose one leg of the transformer or one leg of the supply. The other day they blew a cut out at the pole and lost a whole leg of service. While doing our initial investigation we noticed that on the 3-phase panel B-phase has no voltage to ground. Single-phase My first reaction was to replace the fuse and clip an amp probe on to see what was happening. Some time ago, we installed, what I think was a 1:1 3 phase transformer to get rid of the high leg of an open delta system, for a particular machine. If a phase is lost, then the motor tries to start, the motor burns up almost 100% of the time. 6 amps. The rectifier consists of 3 individual rectifier blocks. They are burning up 3 phase motors. When the voltage drops, current goes up to try and maintain torque, thus high current draw, thus blowing fuses on one or two of the 3 phases. When measuring phase to ground on each phase of the secondary side we have one phase that measures zero, the other two measure 480V. Here we’ve added 3 troubleshooters to do so. Make certain that the wild leg is going to a 230/240 needed source & not a 120v application. Have you checked continuity between all legs of your motor leads (when connected for the proper voltage). To be code compliant, the high leg must be the B phase, and it must be colored orange. 120v on one line 0v on the other. The only other thing I can think of is lightning storms weve had Dangers of Running a Motor with One Phase Lost Permanent Damage Risks. Y wound motors work much better than a Delta wound motors in this approach. So the Utility feed has one high leg. A phase failure is an interruption of a single conductor. If you test the voltage between Line 1 and Line 2 with a voltmeter it will read approximately 460 volts. For Online Courses Download Our App : https://play. It's most likely the Y system if it's a modern Download scientific diagram | Three-leg 3-phase inverter circuit topology. The power company said that we had lost a leg, but the symptoms looked more like a dropped neutral. I wouldn't recommend touching the phase wire, but theoretically you could with no danger, if you were grounded also. What will actually happen? The amperage the motor will draw, remains the same, but the kva capacity of the transformer is reduced by 1/3? I It's very common to have a single phase panel right next to a 3 phase panel. 5% can produce a 25% or greater increase in motor temperature. POWER_PIG Senior Member. But in any case, it's because the capacitor is there to generate the 3rd leg, so a loss of one is Other loads on the same circuit already running when the phase was lost on that circuit will keep running, and acting like a "rotary phase converter" to create a voltage on the missing leg so that a load that is energized under those conditions might start and rotate. For single phase 240 volts I combine two legs 120 volts each out of the panel. Let’s look at a simplified example of how 3 phase power is generated. Allowing motors to run with a lost phase there is a tendency for the motor itself to re-generate the voltage on the missing phase – albiet at a lower potential. This takes 3 wires instead of the 4 wires used in Y configurations and allows the traditional opposing phases for 120V power to be more easily extracted than real Delta configurations. It's a three-phase power configuration where the center point of one phase is grounded. Other types of three-phase supplies are wye connections, ungrounded delta connections, "ghost" leg configuration delta connections (two transformers supplying three phase power), or corner This is actually the origin of coupling: if you have a 3 phase load, say a motor, you can connect each winding across phases, I have seen in a 440 open deltas appear to have a phase lost as high loaded phases show very low voltage and unloaded was over 440. When a 3-phase motor loses one phase of its power supply, it can have several significant consequences that affect its operation and performance. Three-phase electric power (abbreviated 3ϕ [1]) is a common type of alternating current (AC) used in A 3-phase motor is provided with a FVNR starter. Can any of you explain this? My experience is mostly with eutectic alloy overloads. For 3 phase machinery and equipment I use all 3 legs including the third 240 volt wild leg. I assumed this was a high-leg delta system. edvin. A 120/240 delta system with "high-leg" would have 120V from A and C phase to neutral/ground, with B phase being the high leg at 208 to neutral. This feeds the igbts through capacitors and etc. If you measure more you need to reduce the inlet 480V to 400V. 00 amps, and the total power used will be 12,000 watts. On a incoming service 3phase 240V phase to Phase. Increased Energy Costs. From those measurements, the ONLY possibility is that you have a 240/120V 3 phase 4 wire delta source with a center tapped leg between two of the phases. From your voltage measurements it looks like a center tapped single phase source is connected to a 3 phase panel. There should be continuity, if there isn't, it could be a 'open' on one winding. Rotor Damage: Continuous operation under stress can deform or misalign the rotor. Is there a reason to skip the high leg with a 2 pole breaker? This is typical behavior when one leg of the three phase is lost. W7, by "one primary phase supply to the transformer is opened, i. We have and old facility with a 1948 ITE 200KVA 4160V Primary Delta to a 480V 3 phase secondary. The remaining phase-to-neutral voltage will be √3/2 the phase-to-phase voltage, that is, if A-B-C is 240 volts, then A-N and C-N will be 120 volts, but B-N will be 208 volts. LOST NEUTRAL SHOCKS HOMEOWNER - a 3-phase motor "converted" to The incoming power is 230V 3-phase with a "high leg", i. Lost a high leg on 3 phase . In this case, the warming up is, at the most equal, to the warming up during a I have a guy on a job - 3phase 240/120v high leg. VA in a 3 phase circuit is Amps x Volts x 1. These are normally definite time relays instead of the usual inverse time. . These have also been checked with a load (Compressor, no difference) A to ground - 122V B to ground - 121v C to ground - 206v (little low) A to So ALL of that power through the rectifier must now come from a single phase source, i. Before I went to check the main panel, I had a good feeling we lost one leg coming into the house. This is 1/2 of 250. google. To get VA in a 1 phase circuit, it's Amps x Volts. it is only high in relationship to ground (208V compared to 120V) which is irrelevant to a 3 phase load. How to troubleshoot a leg that has lost power? There are quite a few ways to solve this problem. Feb 9, 2012 You have lost either A or C phase and there is a connected load between the two bringing them to the same potential as which ever phase is still good. So each unit has 120/208v single phase. The unit had a 3-phase, 208V input. All the phase-to-phase voltages would be 240. 732. For some phase loss relays, this may go undetected since the relay Yes, we know. When a phase is lost feeding a house, the utility hooks up a temp transformer by your meter and creates 240v with only having 1 leg and neutral. Figure 1: Picture of a three-phase motor next to a reversing motor starter with thermal overload block. 5. It is also used to power large electric motors and other heavy phase loads. from publication: Improved Optimal Control Technique for Control of Parallel Three-phase Inverters | This paper proposes America uses 3, which we get a lot of weird effects when 1 wire breaks. the neutral wire is attached to the center point of one of those three windings i mentioned above, and grounded. The generator did not kick Phase loss is simple: the loss of a phase (or pole, leg) in a 3 phase system often cause by a blown fuse, overload relay malfunction, old worn contacts or simply mechanical The Utility primary has a voltage monitor and it shows it as supplying 4888 on two legs and 4964 on the 3rd leg on a 4800V system. If you were to measure phase to phase voltages you would see them all to be 208V or thereabouts. I am trying to correct the PF which is . look at the bussing. That requires only the basic Ohm’s law; you can simply use our kW to amps calculator here for conversion. Location Ft Collins, CO. Figure 7 – Delta connection – three phase, three wires. 2 of the previous 3 phases. Make sure the resistor is this many ohms or less. Anything that requires the p-p It's far more common that the unit overheats trying to start on the lost leg. I had a Phase Perfect converter & used a 75kva Delta to Wye transformer after it to get rid of the hot leg. 120 degrees separates the legs in three phase, hence the 208 instead of 240 line to line. The starter heaters were tripping and shutting down the starter. Got an interesting question. Single- phase loads are connected to one leg of the wye between line and neutral. I do not want to find out that this type of 3-phase will not work after purchasing. like how it actually makes the “new” leg 180 degrees out of phase with itself to create 240, but I bet someone here does. so I got the main MDP and sure enough B phase nothing So I tell the maintenance guy to call Dominion they lost a leg he high leg delta 230v / 3 phase / 4 wire service looks like a triangle, with three windings connected end to end on the secondary of the utility transformer. I am working on a tenant improvement project with a 240/120V, 3 Phase system. The igbts then invert it to a simulated 3 phase output to motor which will allow it to run with a single phase input. If you're in an apartment, chances are that the whole building is fed with 120/208v 3-phase, ie 3 legs of 120v. Once running, a 3 phase motor will generate a third leg which you can use to run other 3 phase motors. They told me that it was pulling 16 amps I picked up a 3 phase 220/440 machine with a 5HP motor I need to run. The incoming service is 600 A. One-half of the copper is required, and the wire transmission losses will be halved. The I don't think that would be a smart idea in this case. A single phase 480 volt 8,000 watt heater will draw 16. There is one part of the situation that I am trying to work out for myself. ) Is there any reason not to run a 240 welding machine off one 120 leg and the hot leg? It still gives me 240 between the legs, but if any electronics in the welding machine are powered by one of the 120 legs, it'll fry them. The 3 phase ac input is converted to a single phase dc, called the dc bus. The grounded leg is no more dangerous than the grounded neutral leg in a 120 volt circuit. I pulled the panel cover off and got my meter out. Given that a 3-phase calculation to determine the current on each leg is (I=P/E x 1. There is a main Figure 2 – Shorted coil example. So if you have a 230V 3 phase motor, the phase-to-phase voltage is 240V as it should be. 73). If one phase of the supply is lost, then the current on the other two phases will be 25. Seriously, it does, I have a bunch of 3 phase shop equipment, and this was far better than a phase converter. Join Date Nov 2002 Location Green Bay, WI Posts 4,344. 0, the neutral is at 0. How 3 Phase Power Works. I have 3 phase with a hot leg (120, 120, and 208 to ground, but still 240 between each leg. For 120 volt single phase lighting I just use one leg 120 volt out of the panel. What is a single-phase fault? A single-phase event occurs when one leg of a three-phase system is disconnected or otherwise lost. Utility generating stations generate 3 phase power using high-pressure steam and low-pressure steam to turn large turbines called generators. K. BTW, in true 120 deg 3 phase, two 120 volt legs will measure about 208, not 240, between legs because they are 120 opposed, not 180. Anyway we are trying to figure out the best way to use the 3 phase machine right up "High leg" has absolutely nothing to do with a 3 phase load, there is nothing "high" about the "leg" with regard to the other two phases. The rectifier is for a generator and all the specs I have to work with is that the DC output will be Essentially the circuit between the drive and motor is open somewhere on the phase indicated by the fault. It looks like your design will work ok. Has anyone else encountered this 'Getting rid of the high leg' reads quite a bit differently than: " My machine HAS to HAVE 208Y120 power to feed its VFD and complex controls My shop has utility of the street electric 400 amp-240 volt-3 phase delta with a wild leg. e. In a delta system, one leg can be lost because of a blown fuse and still deliver full voltage on all 3 legs. This has the interesting effect that the phase which has been disconnected - potentially by the operation of a fuse due to a fault - is now being fed by the induction motor. Now onto the weird part. If the 208 volt load is small in relation to the service then it should work fine, the load does not "know" whether it is wired phase to neutral on a 120/208 service, or hot leg to neutral on a 120/240 delta service. Existing panels in the building had markers on them that say "HI LEG PHASE B". Bearing Wear: Increased vibration accelerates wear and tear on bearings. High leg delta systems make sense when you have need of many 3 phase circuits, but only a few 120 volt circuits. Unbalances in other connected loads can also affect the motor. Although 208 volts is present between the high leg and the neutral, a 120/240 delta service is not intended for operation of 208 volt loads. The Wye configuration is used to distribute power to everyday single-phase appliances found in the home and office. Wye and Delta comparison. It goes into detail on several combinations of lost phase on a 3 phase system. If you use a high-leg delta connection (see the previous picture), you have 3 phase and 1 neutral and 1 ground. But it doesn't appear in the '71. That is not “Wye” at all and if they were referring to the primary side of the transformer being Wye, that was irrelevant and superfluous information that only confuses things. pcviu As we know our 3 phase Induction motor required 3 phase p When testing leg to leg you should get 230/240 on all 3 & leg to ground is 120 on 2 but the wild will be 170. If a 3-phase power panel provides a neutral wire in addition to the three lines and ground, then it indicates either a 4-wire Y configuration or a 4-wire Wild-Leg Delta configuration. I had to do some work in the south plant and needed some 240 volt branch circuits. It’s quite easy to convert kW to amps and amps to kW in a simple 1-phase AC circuit (compared to a 3-phase power calculation). G. A couple buddies looked at my panel and I have 120V on each outer leg and 240V on the center and there is orange tape. How To Solve Power Loss Of One Leg: 3 Solutions . When one of the power legs loses its power, it can lead to many problems. A voltage unbalance of 3. The weirdest effect is a lost neutral, where both hot legs are still hot, but the 120V voltage wanders all over the place high and low - the two legs adding up to ~240V, but one higher and one lower. 120/240 Delta is the way the poco can supply 3 phase and single phase in one bank. 0 mark on the graph) then your graph difference is only 1. At first, this may appear to be a poor definition, as 2 of 3 phases are still present. The electrician wrote that he wants a transformer on each floor to be 480V, 3 phase primary to 120/240V secondary with high leg because that's the equipment they have available , he wrote "Transformer will produce three legs 120V not There is a 120/240 volt 3 phase delta panel in the south plant. An upstream breaker is provided within the panel feeding the motor providing SC and GF protection, and is also sized per code. Cite. If a phase is lost while If one line of a 3-phase induction motor is accidentally opened or if a fuse blows while the motor is running, the eclectic machine will continue to run as a single-phase motor. I’m not an electrician, so I’m probably using the wrong terminology. Small to medium sized The leg-to-neutral voltage of a 3-phase wye transformer should be the phase-to-phase voltage divided by the square root of 3 (roughly 1. 9 amps. Does that sound right? Yes, it is a 3-phase inverter installed around 2012 or 2013. The air compressor cuts in and out. The wild leg transformers are smaller becouse the 3 phase loading is smaller. The most common cause of unbalance for three-phase motors is the loss of phase resulting from an open fuse, circuit breaker, connector, or damaged conductor. Three-phase transformer with four-wire output for 208Y/120 volt service: one wire for neutral, others for A, B and C phases. There is no f***ing way your going to even out the loads across the 3 phases. 90 on the legs used for In a three-phase 120° system, only 3 wires are required to transmit the power that would otherwise require 6 wires. Page 20 is where delta wye starts. 73) If the motor is not already running when the "phase" is lost it won't even develop any torque to start, Can a 3 phase power cord be split to have two 3 phase outputs, like a Y splitter for 3 phase: General Electronics Chat: 3: Oct 2, 2024: O: Using Voltage and Current Transducer, Want to measure Power and phase angle: Homework Help: 43: Jul 26, 2024: F: 3 phase power: Homework Help: 1: May 7, 2024: J: is the power delivered by 1 no. I was told its a high leg configuration and that went right over my head. 3 Phase Lost Leg Their anatomies retain vestiges of the four-legged land animals in their ancestry, the ones that began the bold return to the sea more than 50 million years ago. May 6, If you lost a phase, then you are still getting 110-120, and components at that voltage will sometimes still work. Say, I have a motor running with a lost leg. I assume whatever components that need 120v in the welder will not be able to run off of the 208v leg without frying a circuit board or I got home last night and half my lights don't work. Mar 2, 2008 #3 I do not know, I can't find My explanation would be this is a WYE system, fed from a 3 phase transformer, with only two phases delivered to the unit. However, that’s not how things appear Phase failure. I cannot remember if the 400 series had a phase lost fault code. I'm an electrician who owns a retail store in a shopping mall, and I had ASSUMED that each of our units was fed with a 240V 3W service based on the panel in our unit, the label, and the fact that it's only a 2 pole main breaker. Each UNIT is fed with just 2 legs of 120v. Only the 3rd leg is out though. 67 amps, and three such heaters connected in delta to a 3 phase 480 volt supply will draw 28. The power that enters a data center is usually 3 phase AC power, which means 3 phase alternating current power. The lost neutral is an immediate and imminent threat to your safety. There is no 240V accessible in your service. You can use a 2 pole breaker on the high leg and one of the other phases, but it must be rated at 240 volt, not 120/240. I’ll also explain the mystery behind why the 3 power lines are 120 degrees apart because that’s a crucial piece to understanding 3 phase power. In the graph the difference is 1. Kele offers several voltage monitors ( TimeMark 258 and 269 , and Littlefuse 201A, 460, 250A, 355-200, 355-400, & 355-600 ) that detect phase loss and other harmful voltage conditions regardless of regenerated voltage. Presume that phase C is lost. Keith . In a 3-phase AC circuit (usually a 3-phase motor), converting amps to kW and kW to amps is not all that easy. Given that each 3-phase leg is connected to a 1000 watt resistor load. If you have a 3 phase wye, and line to neutral is 125, then you can not read 250 line to line. The transformer bank may be supplying multiple buildings. These are designed for 3 Phase 240/120 (Hi-Leg) Loads but someone might have installed one on your service. If the phase that is grounded shorts to the equipment frame there will be no hazard because that phase wire is the "ground". one leg is 220V and two other legs are 120V. One row of overhead lighting was slightly more dim than the others. Here are the readings on the incoming lines, before the main. that'll get you 230v / 3 phase / 3 wire. The current drawn from the remaining two lines (phases) will I installed a 22kw LC 120/240v 3 phase Generac with a 3 phase 200A ATS at a site. 2. Guyute Member. It is good, but if you measure the voltage between 1 phase and neutral you need to measure 240V. Share. 2 legs are 120 against neutral one leg is 208 V. My first suspect would be the phase converter though! Stuart Is this one of those rules that was decided on in the early days of the NEC, and the reason is long lost? 480sparky Senior Mar 2, 2008 #2 In my '75 NEC, the requirement for the B phase to be the high leg is in 384. A single phase was lost from the utility service and hours goes on indefinitely. Reply. So unit 1 is fed with A-B, unit 2 is fed with B-C, unit 3 is fed with C-A, unit 4 is fed with A-B, and so on and so forth. If you need mostly 120 volt circuits, consider a transformer to get a 120/208 system. I'm trying to speck out a heat sink for a 3 phase rectifier. 85 and . Reply reply Anyway, since you askedone of the most common reasons for high current draw on one leg of a 3 ph motor is a phase imbalance on the line side. 25 Ie. If you rate the resistor in Amps just multiply the charging current by 3. If you have a 3 phase delta supply you can not have two center taps of different phases connect together. Go back to Three phase power measurements ↑. Your options are: 1) get a 208V to 240V transformer 2) replace your 240V heating element(s) with 208V 3) be satisfied with the lower heating ability of the 240V element(s) operating at 208V The preferred term is "High-leg delta". According to the nameplate info the max. A three-phase unit that runs on 230-240V should be able to run on a delta system as long as any 120V inputs are done correctly and not with the high leg phase. Running a motor in a single-phase condition Anyways the maintenance guy tells me they just installed this 480v baler that has three different service disconnects it's huge anyway I start to troubleshoot and immediately I find the problem or at least I thought I did ,no power on b phase . About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright Phase loss alarm The phase loss alarm is an under setpoint alarm that monitors the voltages on a 3-phase system and triggers the alarm when one or two phases fall below the pickup setpoint setting and remain there long enough to satisfy the pickup time delay period. I need a heat sink for each block. (In my case anyhow). The cause is, for example, blown fuse. I worked for a large aircraft manufacturer that had many 3 phase motors driving machine tools. TXROCKS TXROCKS In general, the following applies for motors with an output of // Pe ≤ 10kW They do not require a special phase failure protection, as long as the two-phase trip current is ≤ 1. The motor would not care to which lead the "high leg" was connected, as long as the phase rotation was correct for the required motor rotation. But AC drives seem to work ok, The "hot leg" to ground is 208v and the other two legs are 120v to ground. NOTE: *In 1PH system configuration, no phase loss alarm is triggered because it is considered as no load condition. When a 3 phase induction motor is running and suffers a loss of phase, then apart from all the things we typically consider such as additional load, it effectively becomes a rotary phase converter. Follow answered Jul 7, 2015 at 13:49. They are using GE drives (AF300's I believe) rated at 15hp, I hate them having almost lost my life due to one some years ago and will not start up any DC drive on them. Lighting was 277 single phase from line to neutral. The motor then continues running with two phases and can suffer damage. I had an analog meter with me showing two of the legs drawing approx 24 amps and one drawing approx 18 amps. After testing I found that A and C phase had about 65 volts to ground and B phase had 120. However, in measuring between lines If you measure voltage between the 1st phase and the 2nd phase you’d get 480 volts. BUT if you measured the voltage between the 1st phase and neutral (which would be similar to a 4th phase at the 0. Tspisak has already said that it is a 3-phase disconnect, which will disconnect all 3 phases. I was looking at adding a Miller invision 456P. A 3-wire 3-phase circuit is usually more economical than an equivalent 2 wire. 0. 3(f). The OP may have the same phase feeding both legs of the machine, with no difference in potential, the 0 volt reading. Hello, electrical gurus! Im working on an apartment building. Thermal overloads (not solid state) are provided with the controller and are sized per code. Transformer is a 3-Leg Core Construction Type; Since the HV winding still develops voltage across the winding even though the phase was lost, the corresponding LV winding will also develop voltage across it, and the LV phase/line currents will be relatively balanced - as if the phase was never lost. Ground (Motor Winding Shorted to Frame) When a motor is “grounded“, the winding is shorted either to the laminated core or to the motor’s frame. These drives have a dedicated fault I had to walk an electrician, and subsequently a junior technician, through the diagnosis of a three phase motor problem today. The high leg has only a 15 HP compressor connected. Could the main have tripped and lost a phase? Indicating lights for corner grounded delta or high leg delta, for example, are not required Reply reply More replies. There isn’t enough current to actually trip the phase protection breakers/fuses. nhsr mjqbqd vanbnb saxp nxjy nqeko equokua xypnjcts blnarc zmsr