One more point too, if your at all unsure please get a certified electrician in. Probably better to take it out. The hazard of this is that if single phase loads are connected to the high leg with the connecting person unaware that that leg is higher voltage , excess voltage is supplied to that load. It generally exists at the service entrance, but may not run to the panel or load. Yes the B phase will fry anything connected to B phase and neutral. Your 3 phase service panel is basically one third useless when needed for 120v loads. You can tell who I am, because of name recognition.
Generally, these cases are identified by three transformers supplying the service, two of which are sized significantly smaller than the third, and the third larger transformer will be center tap grounded. I know that phases A and C to neutral you get 120 and that phase B to neutral you get 208. Center-tapped delta transformer voltages High-leg delta service is supplied in one of two ways. The standard replacement system takes one more transformer can but it makes the installation standard, very common and the metering less exotic. One transformer is connected to one phase of the overhead primary distribution circuit to provide the 'lighting' side of the circuit this will be the larger of the two transformers , and a second transformer is connected to another phase on the circuit and its secondary is connected to one side of the 'lighting' transformer secondary, and the other side of this transformer is brought out as the 'high leg'.
Do not know what was used there and haven't had the cause to use it, I have 480 3 phase avalible and use it only on the large cnc floor mill which was wiredup by a pro. Your constant challenging most edits in these subjects, combined with your seeming lack of and these other problematic habits, makes this behavior. I assume that the machine has starters with overload protection built into it. Doug My friend has 3 ph in his shop and it has a wild leg , much higher than the other. There is a wiring diagram in the motor, 9 wires. High Leg 3 Phase Wire Diagrams can be very useful guide, and high leg 3 phase wire diagrams play an important role in your products.
By convention, the high leg is usually set in the center B phase lug in the involved panel, regardless of the L1-L2-L3 designation at the transformer. Wire is good, of any size, for 80% if its full load rating when the load varies, such as a receptacle circuit. However, it also refers to Table 240. To carry away objectionable, dangerous, fault currents of short duration. Delta Configured Three-Phase Power from a Phase Converter Nearly all phase converters produce three-phase power by generating a voltage that is added to the two legs of single-phase. In this configuration, ground and neutral are not referenced equally to the three legs, but are half-way between the voltage derived from two of the legs.
That's all it takes to get a second 60 degree potential. It's cheap insurance against any voltage drop issues. If your machines can be configured to run from a delta service, then just wire them up like the neutral is not there. When do you find a high leg in a service. . We just called them 3 phase 4-wire delta as they are defined by government metering standards people in Canada by the shape of the system phasors.
The center tap allows A and C phase to have a neutral and therefore 120 V available. Yes the B phase is high. The B phase is read all over from 190v to 240v to neutral. I have already explained that the ability to use 240v over 208v is not an advantage that can be attributed to high-leg delta, because a specific voltage value is of no inherent value. There are lots of other sizing requirements also so error on the generous side of things.
Yes the B phase will fry anything connected to B phase and neutral. If so we invite you to join our community and see what it has to offer. Some are tapped for 208, 277, 120, etc. Forget the neutral when wiring motors. Just fellow tradesmen who enjoy talking about their business, their trade, and anything else that comes up. Current practices aren't necessarily based on technical reasons, but for historical reasons and those merit detailed discussion here much like 120v vs 230v at home, 50 Hz vs 60Hz discussion.
Motor does not use it, does not care. Does any one have a good explaination? Will you let me post my addition if I clarify that I am talking about the case of separate transformers and include specific warning about poor load capacity? So if A-B, B-C and C-A are all 240 volts, then A-N and C-N will both be 120 volts, but B-N will be 208 volts. Yes, I am a noob, I openly admit it. If the machine has a 240 volt control transformer then it will make no difference where the high leg is connected. It looks like its a an experience based reflection someone wrote. Your 3 phase service panel is basically one third useless when needed for 120v loads. In order to have 120 volts from phase to neutral on both systems, the phase-to-phase voltages of the systems must be different.
I guess that any single phase 208 V equipment would work on a single pole breaker, but that is a novel and non-standard application. The second one points out Figure 10-18. I think it should be included but it needs to be simpified somewhat. Wild Leg only matters for 120v connections. Register a Free 1 month Trial Account.
I don't believe this was ever an intended application and I'd appreciate a better reference showing this was common or done at all for high-leg delta systems. Why would one use this? For help in selecting part numbers for a job quote, please attach plans, specifications, and electrical drawings, if available. As noted above by me and another reviewer, the cure for regionalism is to add information about the rest of the world, not to delete good information about the region that is represented. Even though the voltage is high on B phase in relation to phase A and C. If you want to know more or withdraw your consent to all or some of the cookies, please refer to the. Wye Three-Phase Three-phase power is most commonly provided by the electric utility in a wye configuration.