Since current is being used as the basis for analysis, the wye-connected circuit is selected as the starting point, since in a wye-connected circuit, the line currents leaving the transformer and the phase currents owing in the transformer windings are equal. It is of my opinion should only feed the pri H1-H2-H3 with L1-L2-L3 conductors leving the H0 unconnected and isolated. In utility systems, the neutral wire is the same as the ground wire, and the neutral is common to both primary and secondary. Arbor saw motors can be very strange even with correct voltages. It is most common configuration. Usually, the coils shown are secondary windings of three different , the primary windings connected to a set of three-phase high voltage power lines. This relationship between line and phase currents simplifies the analysis.
Figure 2 shows a delta—delta transformer connection. I speculate that this hole may have been caused by the excessive neutral to ground surge or low frequency voltages warned of in the nameplate. In this case, the zero-sequence voltage equals the line-to-neutral voltage. It's only a three-phase load if it uses all three poles from it's source. Join your peers on the Internet's largest technical engineering professional community. If the network transformers are delta-grounded wye connected, the network will backfeed the circuit during a line-to-ground fault.
I wouldn't be at all concerned about Y-Y padmounts with the proper precautions. Wye-wye transformers are very common. Our site is specifically designed for you and it's the leading place for electricians to meet online. For example, you might put your computer loads which have switching power supplies on a delta-delta transformer, which you would feed from a delta-wye transformer. The next day the ground was smoking from a red hot bonding electrode he installed from the xfmr to the building service. When the high voltage phasors lag the low voltage phasors, the connection is considered to be non-standard. Notes: Be sure to ask your students to describe how they arrived at the answers to this question.
Maybe you know, where is this country. The first method is to connect three single-phase transformers to form a three-phase bank. A good example of an exception is a generator step-up transformer. Some additional notes, some one else has put together, on backfeeding transformers. Discuss anything related to the field of Electrical and Computer Engineering. They were more worried about not being able to detect ground faults, which could present a potentially dangerous situation. Failure seldom stops us, it is the fear for failure that stops us - Jack Lemmon Make the best use of Eng-Tips.
One possible delta-wye transformer configuration. Question:can we use generally same wiring with neutral blue wire in machine for devices on 120, 208, 230 240 V? And definitely need to consider fault current interruption because introduction of new ground on the wye can increase available fault current. I was not there as an electrician, and it would be inappropriate for me to attempt to do any work on this equipment or in this facility. I can't imagine that the add-on would have an effect on the existing relay scheme to any significant degree. My bet: a slight bit of leakage and there is always something is causing a voltage excursion up to the full 480V, causing some protection relay intended for 277V to trip out.
The concerns about wye-wye transformers are generally: Triplen harmonics can pass through the transformer - in the old days, this could cause problems with telephone interference on overhead power lines, but this is not common problem these days. I am producer of woodworking machines. May be due to difference in insulation as wye-wye coils need insulation for L-N voltages. Ground protection relaying in the neutral of the primary circuit may then operate for faults on the secondary circuit. By the way, this is one of the best, if not the best, transformer books I've seen Cost might be an issue, especially on the higher voltages.
Sorry I can't help with your problem. Step 3: Split 1Ø, 208V loads largest to smallest : one-half on each phase A to B, B to C, and A to C. The other lead from each of the single-phase transformers is connected to the line conductors. Adding a third tertiary winding connected in delta alleviates many of the concerns mentioned. Another issue is proper transformer loading.
In other words, a high voltage winding and a low voltage winding that are drawn parallel to each other constitute a single-phase transformer or two windings on the same leg of the magnetic core of a three-phase transformer. This is a very unusual setup to the best of my knowledge in that ungrounded systems are normally fed from delta-transformer windings. Regards Ralph Failure seldom stops us, it is the fear for failure that stops us - Jack Lemmon Make the best use of Eng-Tips. I wonder if you can show how to set those lower voltage 9480 to 500 vac tripping set point for breaker. I can imagine several scenarios where there would be an 'impedance derived neutral' inside the oven, where things would work most of the time, but where transient problems could show up. I did pull the standard on transformer connections that you mentioned today. The standard recommends that any transformer wye or delta which feeds an ungrounded system should be specified an purhcased for ungrounded use basedon this capacitive arcing phenomenon.
A 277 volt load is still a single phase load. Sometimes nonstandard connections are necessary to match the phasings on two different systems that must be electrically tied, but normally, standard connections are specified. This would greatly reduce the presence of harmonics in the primary system, partly due to the absence of a neutral connection. Different products have different specs - if you're an engineer, keep discussions purely based on merit. My questions are: 1 - Can anyone explain the nature of the expected surge and low frequency neutral to ground voltages in this configuration? The bank will transmit harmonics from one side to the other, whereas a delta-wye won't. Last month's Code Calculations article covered transformer calculation definitions and some specifics of delta transformer calculations. The three-wire configuration can be used on three-phase and single-phase circuits.
Keeping in mind that I a, I b, and I c represent a balanced set of phasors, arbitrary per-unit values are selected to represent a-b-c phase sequencing: Eqs. With sinusoidal phase-to-phase voltage, the third-harmonic component of the phase-to-neutral voltage is about 60%, so the effective voltage across the winding is calculated as follows: There can be a large voltage drop for unbalanced phase-to-neutral loads. The configuration of the four windings are 345kv H winding - solid grounded wye. Today I talked to another engineer and realized that the existing relaying is all based on phase current. The three 50 Hz 3-phase subsets are positive sequence, negative sequence and zero sequence. Wiring arrangements can have a considerable effect on output voltage.