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Why rated current should flow in the secondary for short circuit test in transformer?
Wiki User
∙ 10y ago
Open Circuit test is done to find out core losses of the Transformers.which include Eddy Current Losses and Hysteresis Losses only, if during open circuit test secondary will have some load then I2R losses due to load current in secondary as well primary will be included in test results which is not desired while performing Open circuit test.
Wiki User
∙ 13y ago
Wiki User
∙ 10y agoOn the contrary, the secondary of a current transformer must NEVER be opened because a large voltage will appear across its terminals.
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Why should the secondary of a power transformer not to be left on an open circuit?
In general there is no reason why it should not be, though there may be special situations. Perhaps there is confusion with CURRENT transformers which must not be left open circuit because of the high voltages which they will produce. it may trip the CB. although there is no faults but a high current called Inrush current is flow when the the power transfomer energized while its secondry circuit is open
What is the standard output current of a transformer when connected to an ac?
There is no 'standard' output current from a transformer. The secondary (output) current depends on the load, and should not exceed the rated secondary current. To find the rated secondary current, you divide the transformer's rated volt amperes by the rated secondary voltage. The above cited answer need more descriptive ; a) V/Z = I, b) V/Z = I + Magnetizing current of the transformer taken from Primary side of the transformer.
How should I calculate this. A single phase transformer is rated at 99kVA The primary voltage is 6.6kV and the secondary voltage is 220V Assume no losses and calculate The full load primary current?
First find the ratio of the transformer. 6600/220 volts. Second find the secondary current, I = W/E, 99000/220. Third divide the secondary current by the transformer ratio. The answer will be the primary current. To check your answer (W (or VA) = V x A) multiply the primary current times the primary voltage and the secondary current times the secondary voltage and they should both equal the transformer's kVA.
What is the current in the secondary coil if current in primary is 5.0A?
It depends on the turns ratio between the primary and the secondary. If the ratio were 10:1, a step-down transformer, for instance, the current in the secondary would be about 50A. If it were 1:10, a step-up transformer, however, the current in the secondary would be about 0.5A.AnswerThe primary current doesn't determine the secondary current. The secondary current is entirely-dependent on the secondary voltage and the impedance of the load. It is this secondary current that the determines the primary current. So you should be asking, "What value of secondary current would result in a primary current of 5.0 A?"
What is short circuit voltage?
Short circuit voltage is the voltage that has to be applied to the primaries of a transformer, so that the nominal current flows through the secondaries, when they are shorted. This value is important, if transformer secondaries shall be used in parallel. Ideally all transformers with parallel secondaries should have the same short circuit voltage. When their short circuit voltages are different, the transformer with the lower short circuit voltage will be loaded more than their relationship of power ratings would predict. The short circuit voltage is also important in the design of a transformer, because it predicts, how much the secondary voltage will drop at nominal output current. This knowledge helps the designer to find out, how many further windings the secondary needs for a certain voltage in relation to an ideal transformer. Short circuit voltage is also known as impedance voltage.
Why should the secondary of a voltage transformer not be short circuited?
A voltage transformer takes a primary voltage and steps it down to a smaller secondary voltage. This type of transformer will attempt to keep the secondary voltage at a specific ratio of the primary voltage. If you short it, massive current flow in the secondary is required to do this. For a similar reason a CT should never be open circuited - because it attempts to push a specific ratio of primary current through the secondary. If you open circuit the secondary, it takes a massive voltage on the secondary to accomplish this.
Why should the secondary of a power transformer not to be left on an open circuit?
In general there is no reason why it should not be, though there may be special situations. Perhaps there is confusion with CURRENT transformers which must not be left open circuit because of the high voltages which they will produce. it may trip the CB. although there is no faults but a high current called Inrush current is flow when the the power transfomer energized while its secondry circuit is open
Why secondry of current transformer should not be open?
A current transformer will always attempt to push a ratio of the primary current through the secondary. So if there is primary current flowing, and you open circuit the secondary, the CT will attempt to build up voltage to the point where the correct amount of secondary current can flow through the open circuit (meaning you will get an arc). If it succeeds, you'll have a bright light, and some melted copper, and a very startled person who was unfortunate enough to open circuit the CT. This high voltage can also damage or ruin the CT.
What is the standard output current of a transformer when connected to an ac?
There is no 'standard' output current from a transformer. The secondary (output) current depends on the load, and should not exceed the rated secondary current. To find the rated secondary current, you divide the transformer's rated volt amperes by the rated secondary voltage. The above cited answer need more descriptive ; a) V/Z = I, b) V/Z = I + Magnetizing current of the transformer taken from Primary side of the transformer.
Why rated current should flow in the secondary for short circuit?
The short-circuit test runs the rated current through the windings of the transformer to measure the copper-loss, or power lost in the winding resistances. Because the transformer is run at low voltage for this test, there is very little additional power loss in the iron core of the transformer.
What happen if the number of loops in the primary and secondary coils in a transformer are the same?
If the number of turns in the primary is the same as the secondary, this would be an isolation transformer. Primary and secondary voltages should match (minus the inherent transformer losses), as should the current.
In D.C supply the transformer is not connected why?
In a DC power supply a transformer is connected. The only time there would be no transformer used would be if the DC voltage wanted was 120 VDC. The transformer in the power supply is connected to 120 VAC on the primary side and the secondary side of the transformer is connected to either a half wave or a full wave diode bridge. The voltage out of the diode bridge will be the same output voltage potential as the transformer's secondary voltage but it will be a DC (Direct Current) potential.Reading the question in another way, transformers are not connected in a DC circuit. The reason being is that the transformer operates on a collapsing magnetic field. This field induces a voltage into the secondary side of the transformer. Since the DC circuit does not operate on the principle of a collapsing field except when the circuit is opened, the transformer would not operate as a transformer should..
How should I calculate this. A single phase transformer is rated at 99kVA The primary voltage is 6.6kV and the secondary voltage is 220V Assume no losses and calculate The full load primary current?
First find the ratio of the transformer. 6600/220 volts. Second find the secondary current, I = W/E, 99000/220. Third divide the secondary current by the transformer ratio. The answer will be the primary current. To check your answer (W (or VA) = V x A) multiply the primary current times the primary voltage and the secondary current times the secondary voltage and they should both equal the transformer's kVA.
What is the current in the secondary coil if current in primary is 5.0A?
It depends on the turns ratio between the primary and the secondary. If the ratio were 10:1, a step-down transformer, for instance, the current in the secondary would be about 50A. If it were 1:10, a step-up transformer, however, the current in the secondary would be about 0.5A.AnswerThe primary current doesn't determine the secondary current. The secondary current is entirely-dependent on the secondary voltage and the impedance of the load. It is this secondary current that the determines the primary current. So you should be asking, "What value of secondary current would result in a primary current of 5.0 A?"
What is short circuit voltage?
Short circuit voltage is the voltage that has to be applied to the primaries of a transformer, so that the nominal current flows through the secondaries, when they are shorted. This value is important, if transformer secondaries shall be used in parallel. Ideally all transformers with parallel secondaries should have the same short circuit voltage. When their short circuit voltages are different, the transformer with the lower short circuit voltage will be loaded more than their relationship of power ratings would predict. The short circuit voltage is also important in the design of a transformer, because it predicts, how much the secondary voltage will drop at nominal output current. This knowledge helps the designer to find out, how many further windings the secondary needs for a certain voltage in relation to an ideal transformer. Short circuit voltage is also known as impedance voltage.
Why primary current is higher than secondary current in transformer with turns ratio 1?
In a transformer with a turns ratio equal to 1, the primary current comprises the reflected secondary current plus the magnetizing current necessary to sustain the "back EMF developed across the mutual inductance coupling the primary winding to the secondary. Therefore the primary current is always greater than the secondary current in a transformer with a turns ratio equal to 1. This should be evident by applying Kirchhoff's Current Law to the central node of the "T-equivalent" model of a transformer.
What usually happens at consumer end when the current carrying capacity of transformer is exceeded?
What should happen is that the circuit-breaker should trip to cut off the current before the transformer becomes damaged by overheating.
