3 phase lost leg.

3 phase lost leg On high leg, 2 phases to ground neutral are 120 and the one high leg phase is 208. Generally the P-G voltage is irrelevant, but the 296 on the high leg to ground might mean that they have lost their ground reference for the neutral on the split phase, which is possibly why everything is reading high, because it’s all floating and what you are reading is based on the capacitance. When measuring phase to ground on each phase of the secondary side we have one phase that measures zero, the other two measure 480V. If it's the neutral that's down I could understand the ground being used as a temp solution just as they work. I have also read that based on the rated load the converter could need to be rated at a factor of 3 if the load is sufficient enough. Jan 7, 2012 · Why NOT test power to AND FROM the breaker to see if it is supplying power to the line. THREE-PHASE THREE-LEG THREE-LEVEL NEUTRAL POINT CLAMPED RECTIFIER 7. So use caution if you encounter a corner grounded transformer and think maybe the utility company lost one of their phases. The common transformers you see in most construction today are "Y" connected transformers. 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? Feb 9, 2012 · These were common with 240/120 3 phase hi-leg delta panels where there was limited need for 3 phase breakers and more need for single phase, 120v connections. This is a plug in device on a relay base. Jan 22, 2013 · To be clear, if B is my "high" leg, and I were to put a 120V lamp of 1A off leg A, and neutral, a 120V lamp of 1A off leg C and neutral, a 240V heating element of 15A off leg B & C, a 240V stove of 8A off leg B & A and then finally a 7A motor 240V 3-Phase I know that the total of each leg is NOT. The power flow coming into your home is actually two sets of 110 volts, designated as “phase 1” and “phase 2” that share a ground to safely eliminate excess power. In the connection shown Feb 3, 2020 · America uses 3, which we get a lot of weird effects when 1 wire breaks. 5 and 4 seconds respectively. Only two transformers on pole. Sep 25, 2015 · 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. They are burning up 3 phase motors. If you do not have both legs then you do not have a complete circuit and nothing will run at all. Some just fried electronics. A three phase motor will not start, on its own, with only single phase. Himamshu Jun 17, 2021 · Alas, it is not possible in this universe to have a 120/240 three phase system without a high leg. They are rare and seldom used. 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. The mfg is blaming the power company. So I knew the problem was before the starter because it was Jan 30, 2024 · If the phase loss event is prolonged or occurs frequently, damage caused by heat will ultimately destroy the equipment. Two 3 phase motors both dropped a fuse in the same leg, and a 3 phase heater also opened a fuse. Jun 10, 2015 · We have and old facility with a 1948 ITE 200KVA 4160V Primary Delta to a 480V 3 phase secondary. Presume that phase C is lost. Thanks, E Aug 16, 2018 · I have a guy on a job - 3phase 240/120v high leg. 73) 3000 watts / 480 volts x 1. They are using GE drives (AF300's I believe) rated at 15hp, 230V to operate the pumps. Jul 7, 2015 · The Phase to phase voltage is going to be 1. This doesn’t happen with 2-phase, since voltage vectors don’t add to zero. On a service call we discovered that they appear to have 480vac single phase (507v between two legs, and 507v from either of those legs to the third wire - the third wire appears to be zero volts). Nov 21, 2016 · If you do have 3 phase power loss of 1 phase cause what is called "single phasing". Almost half of your home is cut off from the internet due to this issue. Three Phase Three-Wire Connection (Three Wattmeter Method) Although only two wattmeters are required to measure total power in a three-wire system as shown earlier, it is sometimes convenient to use three wattmeters. A to C, B to C have 480. Jul 5, 2011 · You lost a phase someplace. I checked the main lugs before the main breaker and confirmed my prediction. Oct 13, 2010 · Another thing that can cause this (and go unnoticed) is a 480: 208Y/120 or 240 transformer that has a fuse blown on one of the three phase input legs. You can/will get backfeed through 2 and 3 pole loads on the missing phase and voltage to neutral will appear to be normal but if you check phase to phase you will likely see one of them is not right. 732 times the phase-to-neutral voltages: sqrt{3}=1. I have been told the Oct 17, 2007 · The mathematical power relationship is just the basic 1 phase vs 3 phase power because you have gone FROM 3 phase TO single phase. 1 + 18. The motors can run for a long time depending on duty, load , and service factor, but will eventually fail as the current in two of the motor legs will increase about 50%. The Basics of a 3-Phase Motor How 3-Phase Motors Work. The Inside Story on Phase Failure Protection 3 One of the outstanding features of IEC type overload relays is protection of three phase motors in the event of a single phase condition; otherwise known as “open phase” or “phase failure “ in one of the motor leads. These are technically more accurate because they refer to the neutral. I cant see using the bare neutral to carry power. Each of the hot legs uses the other to complete the circuit. Say light will flicker and than lose power and it restores itself? had power comepany out last night to check meter and so forth, I redid did the connection to the power companies connection last Concluded Points: When two phases are lost the motor is as dead as if there is no electric power at all. k. 73 times (173%) the normal FLA (please refer to the figure below). Some disconnects may not have a fuse in that ghost leg. Aug 22, 2019 · Three Phase Motors: Single Phasing. These are 3 phase instatations. If you have the same Voltage and the same VA in both circuits, the 1 phase Amps is the 3 phase Amps x 1. when one is + the other is -. But does a 480 volt three phase Aug 26, 2006 · I think the bottom line is if this is really as you say, then you are talking about single phase and not three phase. One way would be to use a 3-phase fused disconnect with a slug in the grounded leg. the other legs are 230v phase to phase, or 115 phase to ground. If one leg is broken entirely then neither the compressor nor the fan will work at all. 4 Modeling and Analysis of Three Phase Four Leg Inverter The main feature of a three phase inverter, with an additional neutral leg, is its ability to deal with load unbalance in a standalone power supply system [7],[12]. I assumed this was a high-leg delta system. The tech stated Jan 18, 2019 · I am working on a tenant improvement project with a 240/120V, 3 Phase system. 32x1. Say, I have a motor running with a lost leg. Thread starter merc_man; Start date Dec 15, 2022; merc_man merc_man. I may not get anywhere near the 4,000 and 2,500 amp sources I have coming in but mine is rock solid everywhere except for one time in a corner area of a warehouse, there was a blown fuse on one Oct 22, 2015 · I just installed a new 400a 480v Eaton breaker in a 2000a piece of switchgear. If you're in an apartment, chances are that the whole building is fed with 120/208v 3-phase, ie 3 legs of 120v. If I manually start and transfer the load, all is good. Feb 15, 2016 · Pe ≤ 10kW They do not require a special phase failure protection, as long as the two-phase trip current is ≤ 1. Select one: a. Jun 8, 2009 · This is typical behavior when one leg of the three phase is lost. the primary voltage is 14400 stepped down through a Y Y connected set of 500 kva cans we have replaced all the connections. For the second phase the lost time and yellow time are 3. On the line side of the breaker I have 480v between all 3 phases. 208V 3 Phase Power Panel. CPU in adjacent machine froze up and popped Sep 28, 2023 · The lost time and yellow time for the first phase is 2. Each UNIT is fed with just 2 legs of 120v. When one phase of a three-phase motor fails, the motor will continue running as a single-phase motor using the remaining two phases. 4 times, causing the motor to overheat. Here are the readings on the incoming lines, before the main. One sure sign you've lost a leg from the utility is when the lights turn on when you kick on the electric hot water heater or stove. There is no neutral on split phase. Unbalanced Voltages Oct 6, 2024 · For high leg delta power, the electric power providers install three transformers Wye-Delta or Delta-Delta (we will discuss Wye-Delta for this tutorial due to 120V, 208V and 240V, 1 & 3 Phase Supply) or two transformers in Open delta configuration for smaller loads which still needs three phase power supply. So that, 3 Phases Available: Motor runs; 2 Phases Available : Motor runs in a bad way and draws LRA (Running-Load-Amps) and trips the circuit breaker or burns up. 120/208 is derived from two legs of three phase power. In contrast, the 460 V supply is only associated with three-phase equipment. It is pulling 62 amps on lines 1 and 2 and 72 amps on line 3. This is also called ‘single phasing’. 120v on one line 0v on the other. Apparently the saleman was good and said these drives would operate without incident. Feb 17, 2023 · In conclusion, a lost phase in a 3-phase motor can cause a number of issues, including reduced torque, increased current draw, and uneven wear and tear. Phase to phase they all measure 480V. By being aware of the signs of a lost phase and following the tips for identifying and addressing the problem, you can help to prevent further damage to the motor and ensure that it continues Sep 4, 2012 · If you lose one phase of a 3 phase system and try to start the motor it will burn up If you lose one phase of a 3 phase system and the motor is running it is possible that motor will continue to run, If you have one phase of a 3 phase system, nothing will happen. 732. At first, this may appear to be a poor definition, as 2 of 3 phases are still present. Apr 7, 2008 · What will be some of the other adverse effects that would occur besides single phasing? Obviously smaller 3-phase 120/208 transformers would be effected as well. Jun 24, 2020 · What is an acceptable level of uneven current draw for a 3 phase submersible motor? I have a customer with a 50 hp 480 volt submersible pump. I was expecting the phase-ground measurement to be 0V on an un-grounded delta system. Aug 6, 2016 · When a three phase motor looses one of the phase supply voltage then it is called Single Phasing. So the Utility feed has one high leg. May 29, 2011 · To get your best rotation balance the legs on a motor on a open delta connection some three phase motors have stopped during a duty rest period then when the machine started up after a while ran backwards due to voltage change in the phase windings on a open delta remember its like if ya lost one phase of a three phase wye you can spin the Jan 19, 2009 · One of our customers (local grain elevator) has a 3 phase 230v highleg service. Devices intentionally wired to the high leg won't work when the voltage drops. At first I thought this would not work because of the 30% phase shift from Y to delta, but when it goes back from delta to Y, I think it goes back in phase. A,B,C all have 277v to ground. Benefits of 480V Three-phase Power. My first suspect would be the phase converter though! Stuart Jul 3, 2009 · Could you please describe about the phase shift due to winding configurations (vector group). The goal of the three phase four leg inverter is to maintain the desired sinusoidal output voltage waveform Aug 9, 2003 · If you have a 3 phase, 120/240V w/208V high leg, meter base feeding a 3 phase panel and you take out the 3 phase panel and replace it with a single phase panel and cap off the 208 V leg, will the power companys watt hour meter still record the electric usage correctlly? I dont see how it can What is it called when one leg of a 3 phase power circuit blows a fuse? When one phase of a three-phase system is lost, a phase loss occurs. Solution. If you test the voltage between Line 1 and Line 2 with a voltmeter it will read approximately 460 volts. You lost a leg of the 240 line, because you have single phase power. That would leave the delta primary winding around one leg of the magnetic core still fully connected, and so the corresponding secondary winding on that leg would provide a full 120V output on phase B. Jul 11, 2011 · Ok here it is. h taps, cutouts, jumpers, checked the fluid in the Aug 28, 2008 · A three phase motor will continue running if a phase is lost. Apr 23, 2015 · Your lights and appliances are actually running on half your available electric source in order to cut your bill by using the electricity more efficiently. Is the phase angle difference is between HV side phase to phase and LV side phase to phase? (or) is it between HV side Phase to Phase and LV side Phase to neutral for a transformer with a vector group of Dyn1. one leg is 220V and two other legs are 120V. The fuses were sized not too far above the overloads so my guess is that the fuse went before the overload. Jul 12, 2012 · I have a customer that has an existing automation that has been running for years that was designed to operate on 480vac three phase power. What kind of power is this? Is it really 240V with a neutral and a high leg? Or are we talking about 208Y that is 208 leg to leg and 120 leg to neutral. potential A compressed spring, such as used in an electromagnetic relay, has ___ energy because of its physical condition. Apr 24, 2006 · complaint a piece of equipment was not working. When one phase is at it's peak, the other two cross with opposite polarity, but with fewer volts to neutral. To get VA in a 1 phase circuit, it's Amps x Volts. From equation effective green time, = 27+4-3 = 28 seconds. Occasionally we will have a power failure on one leg of the 3 phase and the transfer panel will not sense the failure. We’ll cover how 3 phases are generated, what a Cycle and Hertz mean, plot the voltage wave form as it’s being generated, calculate our single phase and three phase voltages. There are 3 other transformers connected to the primary feeding adjacent buildings. I have a transmitter site fed by Florida Power and Light with 3 phase power. Three-phase electricity consists of three AC voltages of identical frequency and Aug 23, 2011 · We had a water-crest farm in our area that had 20 or 30 pumps that were constantly going out. a. If you read from phase to phase you get your line voltage, whereas if you read from phase to load you get a phase voltage. It's costly and requires a ton of power. Power up another machine same thing. maximum condition of voltage unbalance c. Some of our machines alarmed out. Jan 22, 2023 · 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. Jun 24, 2017 · My question this time is about what will happen when one of the three phase loads get disconnected just like the in the figure below? For (a) which is star-connection, is the phase voltage is still Vline/sqrt(3)? Is Ineutral= -(IR+IB) still valid if IY=0? For (b) which is delta-connection, is the phase current of still Iline/sqrt(3)? We would like to show you a description here but the site won’t allow us. When one leg experiences this issue, there is a risk of the voltage crossing over to 240V. Existing panels in the building had markers on them that say "HI LEG PHASE B". . Our power company lost a leg of the three phase running our shop last summer. Single Phasing a case when any one phase out of the three phases fails. 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. 73 = 208V. I know that when you measure 220 volt three phase, there's always a hot leg that measures around 190 volts. “cross-phase” voltages) will be 120V * 1. Mar 16, 2017 · I asked them to take voltage readings between phase-phase and phase-ground just to make sure it is an un-grounded delta secondary. so i am thinking we are missing a leg. It also shouldn't be switched unless all 3 legs are switched. Could be a strip of copper in lieu of a fuse. A phase inverter will take single phase power and make 3 phase. Jan 24, 2006 · You have what is called a 480Y service coming into your building. The highleg (or wildleg as customer calls it) runs around 190 to 200 volts phase to ground. Oct 5, 2004 · The incoming power is 230V 3-phase with a "high leg", i. I read somewhere once that when a phase is lost the single phasing motors somehow act to create this missing phase when a fuse blows. 56VAC. In this case then Jan 12, 2023 · A 480 V supply could be used for single-phase or three-phase, depending on the connection (Delta or Wye). The motor it is supplying is no longer running properly. 3 Balanced Three-Phase Networks We are accustomed to single-phase power in our homes and offices A single line voltage referenced to a neutral Electrical power is generated, transmitted, and largely consumed (by industrial customers) as three-phase power Three individual line voltages and (possibly) a neutral 3 phase never reads 0 because the phases are 120 degrees out from each other. However, the current drawn from the two remaining phases will increase by 1. 120v devices on the high leg phase that aren't compatible with higher voltages would burn up. Jan 12, 2023 · A 480 V supply could be used for single-phase or three-phase, depending on the connection (Delta or Wye). 732” So 117. I lose some amperage in the transformers I assume. I have read about people using a small single phase motor to get a bigger 3 phase motor going, or using a pull rope wrapped around the motor shaft to pull start the big 3 phase motor. ) Dec 17, 2010 · The 240 stuff will have an open circuit so even if one leg is intact it will still functionally see zero volts. Another way is to employ a phase failure relay at the main distribution board. Feb 25, 2007 · Residential 120/240 is derived from a single leg of three phase power. Regardless of voltage, a three phase service has three ungrounded "lines". 3 phase machinery runs off Delta voltage, which means you only run 3 hot wires and no neutral wire. 3ph 240 reads like 138VAC or something on each phase. In this case, the warming up is, at the most equal, to the warming up during a symmetrical, three-phase load. So of course I begin checking voltage. so I got the main MDP and sure enough B phase nothing So I tell the maintenance guy to call Dominion In a delta system, one leg can be lost because of a blown fuse and still deliver full voltage on all 3 legs. A proper overload detects the phase failure and trips to protect the motor. Between A and C phase I have 480v between B and C I have 480v BUT!! Between A and B phase I have like 2 volts. ) (In the figures, core leg 1 is abbreviated as ΦA, core leg 2 as ΦB, and core leg as ΦC. If one does not supply voltage, and is grounded, it IS a neutral (or grounded conductor to be precise). When one leg is at a particular point, the other legs are in a different phase of the same pattern. If the cycle time is 120 seconds, find the green time allocated for the two phases. 732 = 3. 7 to 2. Also unfortunately, all the evidence points toward the universe expanding forever and NOT at some point ceasing to expand and ultimately shrinking back down resulting in another big bang that perhaps could result in a universe with different laws of physics that would then allow a 120/240 three Sep 15, 2022 · In a 3-phase system the voltage between any two phases is 3 times higher than the voltage of an individual phase by a factor of 1. 732 to get a phase current. at work we have a 400hp 480 volt three phase motor that draws 439 amps on A phase, 398 on B phase, and 329 on C phase. Jul 14, 2017 · Next part of this article will discuss three-phase transformers using the open-delta and open-wye connections, where one of the single-phase transformers making up the three-phase bank is omitted. Single phasing is a condition that occurs when one of the three phases that is supplying voltage to a three-phase motor is lost. 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. 24(D)(3) It looks just like a normal service. When you lose a phase, you can get the other phase backfeeding through any 240-volt appliances that are turned on. A 208V 2. checked. A 3-phase circuit breaker is OK, as long as it's properly rated. If one phase of the supply is lost, then the current on the other two phases will be 25. If your X-N (and Y-N and Z-N) voltage is 120V (common in the US), the X-Y (and Y-Z and Z-X) voltages (a. If you disconnect the neutral line, you only have the full phase to phase voltage available of the WYE connection, which, again in your case, is 400VAC. 67 amps, and three such heaters connected in delta to a 3 phase 480 volt supply will draw 28. Most three phase overload relays are not intended to provide true single phase protection, so the most likely scenario is the motor will eventually overheat and fail. Jul 15, 2020 · 1) Only in three-leg core type Yg-Yg transformers is the voltage of the lost phase re-generated. Local time 3:25 AM User ID 933 Joined Feb 24, 2016 Messages Mar 5, 2024 · A single-phase event occurs when one leg of a three-phase system is disconnected or otherwise lost. One of the 3 phase motors actually lost 2 fuses. phase to phase had 240v any combination. The customer stated that they had someone out there to repair the machine because the motor was not running just humming. Three-phase motors are powered by a 3-phase electrical supply, where currents in three conductors are phase-shifted by 120°. Seriously, it does, I have a bunch of 3 phase shop equipment, and this was far better than a phase converter. he starts talking about a "ghost" leg. Have you checked continuity between all legs of your motor leads (when connected for the proper voltage). There should be continuity, if there isn't, it could be a 'open' on one winding. This resulting loss causes excessive AMP draw on the remaining phases which can quickly cause damage to your motor windings. 86 kVA Total three phase power = 18. You didn't say that you checked voltage from phase to phase while loads were connected just phase to neutral. Spindle drive dies and wont power up. Feb 10, 2023 · The two power-carrying poles are responsible for dividing a house’s electric connections. I will look for a diagram. New one is getting ~216 across both legs, ~122 leg to ground. a 3 phase disconnect was there. 95% Jun 19, 2011 · I got home last night and half my lights don't work. Best guess is this is what's happening. I was trouble shooting loss of power the other day and this plow lost power. The disconnect This is a single phase motor, so no protection beyond the klixon on the back. Check incoming voltage (208 3 phase) each leg is measuring 184volts. Jan 30, 2024 · If the phase loss event is prolonged or occurs frequently, damage caused by heat will ultimately destroy the equipment. There is a main disconnect in the electrical room through which power enters. The brainiacs from TVA were called in and concluded that due to the nature of the loads, only a "true" 3 phase system with 3 phase primary and 3 pots would alleviate the problem. This creates a more efficient power transmission system compared to a single-phase system. each leg pulling ~11. When this occurs the current across the remaining two legs can go to 1. I think the motor has an issue. However, that’s not how things appear inside the three-phase motor. These advantages are highlighted below. 732 (square root of 3) times the phase to neutral voltage on any three phase WYE system. May 30, 2019 · Three phase electricity. Not fun. loss of one phase of a 3Ø system d. operation of a 3Ø motor on 2 of 3 phases b. The lost neutral is an immediate and imminent threat to your safety. Feb 24, 2016 · Generator lost power on one leg. Aug 16, 2022 · Good afternoon all. 732= 203. A to B has 0 volts. For some phase loss relays, this may go undetected since the relay assumes all phases are still connected. Sometimes a motor can run with the loss of 1 leg but it may start in the wrong direction and another time start in the correct direction. 6 amps) correct? If one of the legs opened up then one resistor would be out of the picture. I have two If the saturation headway is 2. The leg of the transformer with the missing transformer is referred to as the phantom leg. Should this work? I believe the winding has burned on the high leg. This means they supply voltage. Hope that helps. Dec 21, 2012 · Case Machine jogged weird and X and Y axis giving shakes. 2) The voltage of the lost phase is re-generated by the flux that goes through the coil on the third leg in accordance with Mar 1, 2009 · phase 3 apparent power = 82 x 230 = 18,860 VA = 18. In a 3 phase system, there are three “hot” wires that are used to distribute power and a neutral wire that is used Jun 2, 2009 · The contactor should be fitted with an overload that sits between the contactor and the motor. You'll see 120 to ground on each leg, and zero or very low voltage between them. Sep 4, 2012 · If you lose one phase of a 3 phase system and try to start the motor it will burn up If you lose one phase of a 3 phase system and the motor is running it is possible that motor will continue to run, If you have one phase of a 3 phase system, nothing will happen. Jan 13, 2017 · Figure 12 – Three-phase, three-wire, 2 wattmeter method. Leg A: 1A + 7A +8A = 16A total Jun 5, 2018 · Suppose we have a single-phase, 3-wire residential electrical system with Leg #1 to neutral at 110v and leg #2 to neutral at 130v. thats why the two 120 volt to N leads have 240 The Inside Story on Phase Failure Protection 3 One of the outstanding features of IEC type overload relays is protection of three phase motors in the event of a single phase condition; otherwise known as “open phase” or “phase failure “ in one of the motor leads. Jan 11, 2009 · Travis, I believe it has to do with the phase angles of the native legs opposed to the manufactured leg. Before I went to check the main panel, I had a good feeling we lost one leg coming into the house. If the motor is loaded above 33% of its rated load when the failure occurs, it Apr 11, 2017 · 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. I assume you have a direct burial power line, rather than one in conduit, with the meter at the property line, rather than at the house. At much expense POCO changed the system and the problems disappeared. all of these d. The motor will draw more than normal current on the working legs and usually overheats. If you look at the letter "Y" it explains how the legs and taps are formed. 36 kVA. Given that a 3-phase calculation to determine the current on each leg is (I=P/E x 1. e. Mar 9, 2024 · When one phase of a three-phase system is lost, a phase loss occurs. VA in a 3 phase circuit is Amps x Volts x 1. 25 Ie. The correct way to test a 3 phase delta system is to make measurements from A to B - B to C and A to C not to ground this would have shown the rookie the power was actually working on all 3 phases. Divide your line voltage by 1. Mar 16, 2025 · Utility service voltage is supposed to be +-5%, so 270V P-P is too high. At present, the two most commonly used multilevel topologies are the three-level neutral-point-clamped (NPC) [4-6] and cascaded topologies. Jan 28, 2004 · A wild leg in electrical terms refers to the leg or tap on a Delta wound transformer. Normally refered to as 8 or 11 pin bases. Sep 23, 2013 · That is exactly what happened. CPU in adjacent machine froze up and popped May 29, 2011 · To get your best rotation balance the legs on a motor on a open delta connection some three phase motors have stopped during a duty rest period then when the machine started up after a while ran backwards due to voltage change in the phase windings on a open delta remember its like if ya lost one phase of a three phase wye you can spin the Feb 22, 2012 · I have a three phase service that show 235 to ground on one leg, 460v the second phase and 235v on the third leg. Better yet he should have a Phase Rotation meter many Industrial Electricians and Trouble Shooters like my self carry around $100-450 dollars these Nov 19, 2024 · It's a delta transformer. Sep 25, 2016 · I haven't had much experience troubleshooting 3-Phase motors. didnt clamp the old one before it blew up. Dec 16, 2015 · 1) 208v 3 phase will show 120v on each leg (phase) but it will only read 208v across two legs; because the phases are never at peak power at the same time. 4 + 16. Oct 16, 2011 · I just did a service 4 days ago, and it keeps losing one leg of the service, this started yesterday. | HVAC-Talk: Heating, Air A 3-phase system is a type of electrical power transmission that uses three alternating currents that are out of phase with each other. It won't even try, it can't try, there is no complete circuit. The” Y” in 208Y/120V refers to the neutral as the center of the Y shaped power source. They sent me back readings for phase-phase at 480V, but phase-ground measured approximately 277V for each leg. We swapped the lines around and the high current stayed on line 3. Jan 6, 2009 · A single phase 480 volt 8,000 watt heater will draw 16. 277/480 Nema Motor Starter. Feb 21, 2015 · I think this is happening between the 208 windings and the 3 leg common core. Role of Balanced Phases May 30, 2022 · 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 . 9 amps. In this tutorial we’re going to be learning more about three phase electricity. Typically, a phase loss is caused by a blown fuse, thermal overload, broken wire, worn contact or mechanical failure. 250. It gives good three phase performance, with 240 volts phase to phase. This is used in commercial industrial application mostly. in any event the pole transformer output, due to the CT [center tap] has the two hot legs of the typical single phase house hold current which peak 180 degrees out of phase. 1 Introduction Many inherent benefits of multilevel converters have led to their increased interest amongst industry utilities. If one or two legs of the 3 phase go out you will see some of your circuits go out and others will work normal. I cannot seem to remember where I read this. Feb 21, 2018 · 208V 3 Phase power also goes by the names 208V 3 Phase 4 Wire and 208Y/120V. Recently received a service call to look at a meat grinder that uses a 3-Phase 120/208V motor. It appears to be exactly what you'd expect from losing one of the lines feeding the primary of a delta-wye transformer. In transformers with four or five leg cores or a bank of three single phase transformers there is no voltage re-generation. The other phase is being created by the 3 leg common core inducing into the 480V Y secondary. Your idler/inverter motor should be running at Three-phase three-wire connection (two wattmeter method) Three-phase three-wire connection (three wattmeter method) Blondel’s Theorem: number of wattmeters required; Three-phase, four-wire connection; Configuring measurement equipment; Three-Phase Systems. A sort of similar but different situation is if you have 3 phase. From the pics (Nova's), it seems that the delta could essentially carry 120/208/240, with the 208 from L2 to Grn. Now onto the weird part. 2 volts three phase so I need to buck from there. The motor's speed and torque production will also be reduced. Similarly given the power in each phase you could easily find the phase currents. If you also know the power factor you can convert between kVA and kW as shown earlier. Axis motor that was squeaking now went to crap. Power company left power on but told them they lost 1 leg? I'm a licensed electrician but I wanted to know best way to solve this ? Jul 27, 2018 · Thanks in advance! I am designing a panel with customer specified 230V 3 Phase Input. Three-phase loads that attempt to start while the building has lost a phase will not be able to do so as three-phase motors rely on all three phases to establish the rotating magnetic field. 73 (square root of 3 to be exact). The former high leg drops from 208 to 120. This is the right answer, the only one to distinguish "losing a leg" (in a single-phase system), which it sounds like is OP's problem, from the phenomenon of "single-phasing," which only occurs in three-phase systems and is the result of a 3-pole device (usually motor) losing one pole, causing a fault between the remaining two as a result of Our power company lost a leg of the three phase running our shop last summer. As a result, only 120V is available when one of the two legs is low voltage. After reading a few threads on this issue, it seems that the general consensus is that this type of problem is most likely caused by a "neutral issue". Voltage between legs is approximately 460v. Since one of the phases is now disconnected, current through other two phases will increase to produce the desired torque. Oct 18, 2023 · Yes. Related Posts: Difference Between Single Phase & Three Phase Induction Motor; Difference Between Single Phase and Three Phase Power Supply; Under Rated Load (1/3 = 33% Load) Jan 30, 2019 · 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 failure. Thanks for Mar 16, 2025 · Utility service voltage is supposed to be +-5%, so 270V P-P is too high. 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. May 31, 2015 · This causes the other leg to increase voltage up to about 189 to 190 volts and the be broken leg is down to about 79 volts This has happened several times over the last couple of years Last night I lost 4 TV's a new cook stove, my internet/wireless equipment and several light bulbs, and a fan for starters Oops! We ran into some problems. If it is a three leg core and if the lost phase is one of the outer windings it might just be 60V with phase angle like the center winding because only half of the magnetic currents flow through the outer leg?! If the lost phase is the inner winding I might be 60V with a phase angle like it should be because it is in-between both phases?! Oct 23, 2010 · “Line-to-line voltages in three phase systems are typically 1. The voltage between any one leg and ground will be 277 volts, and between any 2 hot wires will be 480 volts. This configuration ensures balanced torque production, leading to efficient and reliable motor operation. Feb 25, 2021 · 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. Aug 28, 2017 · During phase loss, a 3-phase motor can regenerate more than 92% of the supply voltage in the open phase. I Jun 8, 2004 · The running motors will generate 3 phase power just like the old rotating single phase to 3 phase converter. Good to know: A device named Single Phase Preventer (Voltage, Current & CT based) is used to prevent the single phasing or one phase failure in a three phase supply system. Can't switch back neither. I pulled the panel cover off and got my meter out. Edit: it reads 138. May 23, 2006 · When measuring the voltage of each leg individually of a 480 three phase circuit, what should the voltage read? It's been a long time since I've done this. A 480 V three-phase power supply has several advantages over other supply forms. It is a 3ph 4 wire service. Once running, a 3 phase motor will generate a third leg which you can use to run other 3 phase motors. • Just as voltages (+currents) may add to zero in polyphase, Transformer fuxes add to zero with 3 phase legs, and we can build 3-phase transformers that are smaller and/or more efcient than 3 1-Φ transformers would be. The “4 Wire” in 208V 3 Phase 4 Wire refers to the neutral as 4th wire. But for phase to neutral, only two phases will give 120 volts phase to neutral (And these will also give you 240 volt single phase 3 wire, as well, which is good for some types of loads)… May 3, 2020 · Core Leg 2: W 2 and W 5 Core Leg 3: W 3 and W 6 (Windings W 7, W 8 and W 9, used herein for zigzag windings, are hard to classify into a particular leg since zigzag windings cross-connect core phase legs. a phase 240 to ground b phase 240 to ground c phase 0 to ground and continunity to ground. 86 = 53. By the way,a high speed motor will produce more appropiate phase angles but a slow speed motor will start easier. 6 amps Customer: why on a 3-phase 480 feed would phase A & B have no voltage on it together,but phase A & C do and B & C do also,could I have lost a leg??? Answered by Sir Sparks in 3 mins 15 years ago Sir Sparks Mar 1, 2016 · A 240 volt high leg delta is a less commonly used three phase arrangement. 4 seconds/vehicle, the start-up lost time is 2 seconds/phase, and the clearance lost time is 1 second/phase, find the capacity of the movement per lane? Solution Total lost time, = 2+1 = 3 seconds. 00 amps, and the total power used will be 12,000 watts. 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 Aug 22, 2019 · Three Phase Motors: Single Phasing. 5 and 3 seconds respectively. Go back to Three phase power measurements ↑. I have 277v to ground on all 3 legs. 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. Sep 2, 2010 · while a pole transformer might be fed from 2 legs of a 3 phase, it is usually not the case. You have 3 hots, a neutral, and a ground wire. Customer: How is the best way to fix a 3 phase panel after it has lost 1 leg on customers side. Related Posts: Difference Between Single Phase & Three Phase Induction Motor; Difference Between Single Phase and Three Phase Power Supply; Under Rated Load (1/3 = 33% Load) Jul 12, 2012 · Note also that the grounded leg is not supposed to be fused. Critical lane volume for the first phase, V C 1 = 1000 vph. May 9, 2016 · Given that each 3-phase leg is connected to a 1000 watt resistor load. This seems correct but my Supervisor, who is intimately familiar with the system doesn't think so, and he spoke with an electrician who concluded the power company has a low voltage issue. Assuming I am adding a three phase buck transformer I can hit nameplate voltage. Basic training programs usually deal with this subject in a simplified manner. All three legs have the same voltage and pattern of 60 hz, but their phasing (timing) is different. bsnbik ehmoae luwhz gaoy bfbw obyp kiwgtc nerfc erwrg ndndluf