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The secondary of a transformer is isolated (floating) relative to the primary, so there is no absolute reference relative to earth ground on the secondary side. By connecting the neutral to ground (earth ground that is) this creates an absolute reference. This also creates a leakage path to earth ground, now that the secondary voltage is referenced to earth ground, but that is more desirable than not because otherwise something else in the system might improperly provide that reference.
Wiki User
∙ 11y ago
Wiki User
∙ 9y agoYou have to connect the other terminal of the primary someplace, be it ground, or be it one of the other hot phases. Convention has it being ground.
Wiki User
∙ 11y agobreaker/fuse should blow
Wiki User
∙ 11y agoplz give me ans
wec, wah cantt
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Can you bank three single phase transformers in a delta to grounded wye with one transformer having a different impedance?
yes
Neutral shift in 3 phase systems?
Neutral shift in a three phase system can occur when service transformers on long distribution lines are connected to provide four wire star service (like 277/480V) and the common primary connection (like three 14.4 kV transformers on a 24 kV line) on the transformers is left ungrounded. Observed Neutral shift can be so severe, depending on the situation, that in the example given here 480 Volts phase to phase and 470 Volts phase to Neutral were measured. This condition is only present while the load (this was a 100 HP pump) is not in service.
What is a 240 volt 3 phase 3 wire grounded b phase system?
It's highly probably that the '240 V' refers to the machine's phase voltage. In which case, its line voltage will be 1.732 times larger -i.e. 415 V. Phase voltages are measured between any line conductor and the neutral conductor, whereas line voltages are measured between any pair of the three line conductors.
Why neutral is not requied in 3 phase?
As far as I understand, you don't need neutral line for connecting appliances that is 3-phase compilant. You only need the neutral line to connect a single phase appliance, which you connect along with one of the three lines.
What is the relationship of primary windings of a transformer to the secondary windings regarding output and input voltage?
The phase relationship between the primary voltage and the secondary voltage of a transformer is 180 degrees (typically) on single phase transformers. If working with three phase transformers, a zero phase shift is often used in Y/Y grounded transformers. If the transformer is wired Delta / Wye, the phase shift will be 30 degrees. I've seen transformers with a phase shift of 150 as well (quite abnormal, but it exists!) due to the starring and a delta / wye configuration. If you are looking at a transformer phasor diagram, this will show the phase shift between primary or secondary (three phase transformers). For single phase, there should be a drawing showing polarity markings - what goes in the polarity marking on the primary comes out on the secondary polarity marking.
Is there a neutral on a three phase transformer?
It depends on whether you are wye or delta connected. A transformer is a transformer, and a three phase transformer is simply three transformers. The key is in how you hook them up.AnswerIt depends on how the transformer is connected. If one set of windings is connected in star (or wye), then the star point is/canbe earthed and becomes the neutral for that particular connection; this is the standard connection for the secondary (low-voltage) of European distribution transformers. In North American three-phase distribution transformers, the secondary windings are connected in delta, and one phase is centre tapped, earthed, and that becomes the neutral point for a 240/120-V split-phase supply to a residence.This answer applies to both three-phase transformers, and to single-phase transformers which have been connected to form a three-phase transformer bank. (It is incorrect to say that a three-phase transformer is simply three single-phase transformers!)
What conductor should be grounded in a four wire three phase system?
The neutral.
Can you bank three single phase transformers in a delta to grounded wye with one transformer having a different impedance?
yes
Why is one terminal of a three-phase AC generator grounded?
only neutral point is gronded not a terminal ,
Neutral shift in 3 phase systems?
Neutral shift in a three phase system can occur when service transformers on long distribution lines are connected to provide four wire star service (like 277/480V) and the common primary connection (like three 14.4 kV transformers on a 24 kV line) on the transformers is left ungrounded. Observed Neutral shift can be so severe, depending on the situation, that in the example given here 480 Volts phase to phase and 470 Volts phase to Neutral were measured. This condition is only present while the load (this was a 100 HP pump) is not in service.
Where does the neutral come from when turning 3 phase into single phase say in a street sub station?
In a split phase service, which is the standard for residences and very small businesses in the US, Canada, and some other areas, one transformer is connected to one phase of the three phase primary distribution mains. The secondary winding is centertapped, with the centertap grounded and called neutral. The other two phases are not involved at all. Do not call the hot legs of the service phases. They are not phases. They are opposite legs of only one phase. <<>> Canada and US transformer connections To best explain this, visualize the three primary line that you see on pole tops in industrial areas. The voltage between these three lines is about 12,460 volts. Eight feet below these top lines that is a single conductor. This conductor is grounded every three poles with ground rods and is used as a ground (neutral) on wye connections. When you see a pod of three transformers mounted together they are combined into a three phase system. From each of the three high voltage lines, the voltage goes through three separate fuses and down to a high voltage bushing in each of the transformers. Inside the transformer the voltage goes through a coil and exits the transformer through a second high voltage bushing. This bushing is tied into the grounded conductor (neutral) and then down to a grounding pad completing the circuit. This connection puts 7200 volts across the transformers primary coil (12460/1.73 = 7200. The secondary voltages of these transformers are determined by the customer that wants the three phase service. It could be 600,480 or 240 volts. Each single transformer has two output bushings. These bushings can be wired into either a delta or star configuration depending on what the customer ordered. In a single phase service, the name is derived from just using one of the three primary lines that are used above. It is the same primary connection, but the secondary is a bit different. The output secondary coil has three bushings coming out of the transformer. On the two outside bushings is the working voltage (house connections 240 volts). The middle bushing is a center tap of the secondary coil. This gives a voltage of (bushing left to center 120 volts) and (bushing center to bushing right 120 volts) The center tap of this transformer is grounded and connected to the single grounded eight foot lower conductor. The single phase service neutral is established at this point. These three secondary points are connected by triplex to the homes weather head where another connection is made to the homes service distribution. This is classed as a 120/240 volt service.
What is a 240 volt 3 phase 3 wire grounded b phase system?
It's highly probably that the '240 V' refers to the machine's phase voltage. In which case, its line voltage will be 1.732 times larger -i.e. 415 V. Phase voltages are measured between any line conductor and the neutral conductor, whereas line voltages are measured between any pair of the three line conductors.
What is the reason why the neutral is not used on high resistance grounding?
The question doesn't provide enough detail to give a definitive answer. The neutral PD is often used in protective functions on high resistance grounded generators (when grounded through a transformer). High resistance grounding limits the use of transformers - you must be using balanced loads, since very little current will flow (typically around 5-20amperes max) to the neutral. Because of this, phase to neutral values (such as voltage) are meaningless. Any current flowing in the neutral will cause an offset in all three phases from neutral. Since the neutral is high resistance grounded, it does not take a significant amount of current to cause significant offset.
Why neutral is not requied in 3 phase?
As far as I understand, you don't need neutral line for connecting appliances that is 3-phase compilant. You only need the neutral line to connect a single phase appliance, which you connect along with one of the three lines.
What is the relationship of primary windings of a transformer to the secondary windings regarding output and input voltage?
The phase relationship between the primary voltage and the secondary voltage of a transformer is 180 degrees (typically) on single phase transformers. If working with three phase transformers, a zero phase shift is often used in Y/Y grounded transformers. If the transformer is wired Delta / Wye, the phase shift will be 30 degrees. I've seen transformers with a phase shift of 150 as well (quite abnormal, but it exists!) due to the starring and a delta / wye configuration. If you are looking at a transformer phasor diagram, this will show the phase shift between primary or secondary (three phase transformers). For single phase, there should be a drawing showing polarity markings - what goes in the polarity marking on the primary comes out on the secondary polarity marking.
How do you tell if you have delta or wye power?
In Europe, low-voltage three-phase distribution is by means of a four-wire system (three line conductors and a neutral) supplied from a wye-connected transformer secondary. In North America, low-voltage is supplied from a delta-connected transformer secondary, one phase of which is centre-tapped and earthed (grounded). The single-phase supply to residences is then supplied by that particular phase, giving 240 V line-to-line and 120 V line-to-neutral. You can tell if you have a delta power when the phase voltage is equal to the line voltage and that you have a star power when the phase voltage =root 3(THE LINE VOLTAGE).
Voltage across Neutral and earth for a 3 phase auto transformer?
A grounded neutral will be at earth potential. A floating neutral will be at a voltage dependent upon the voltage imbalance between phases, and the design of the transformer.
