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Why the secondary of the current transformer should not be open circuited?
Wiki User
∙ 12y ago
The secondary of a CT must always have a load connected. An open circuit secondary can result in the development of a dangerously high secondary voltage. If a CT is energized but is not used, the output terminals of the CT must be shorted out.
Wiki User
∙ 15y ago
Wiki User
∙ 14y agoIts not mandatory in every case, this is recommanded to utilise the electrisity used for energising the transformer. Closed means putting some load.But if we talk about Current Transformer(CT) then yes CT's senondry must be close every time otherwise there will be a high emf in secondary of CT and can damage the instrument as well as operator because its a step up transformer.
Wiki User
∙ 12y agoThe CT will attempt to cause a specific ratio of primary current to flow in the secondary. Since the secondary is open circuited, meaning the resistance across the secondary is very high, the voltage build up across the secondary will increase until it reaches the theoretical limit of approximately the primary voltage, or arcing across the open secondary will occur (usually at the terminal blocks where the shorting block should have been installed).
Wiki User
∙ 12y agoDisconnecting the secondary of a current transformer results in an attempt to generate large voltages across the secondary. This can cause arcing, damage to equipment, or hazardous conditions.
This is because a current transformer is a 1 to many turns ratio device. The primary is one turn, while the secondary is hundreds or thousands of turns. It reduces current but, like any step up transformer (which is what it actually is), it can produce high voltage when not loaded. The intent is to provide a low impedance load across the secondary, so that secondary current is proportional to primary current, as opposed to the inverse condition for voltage, which is what will happen if it is unloaded.
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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 current transformers be shunted before opening the secondary winding?
A current transformer's secondary must never be open-circuited. If the instrument fed by a CT needs to be removed, then the secondary terminals must be short-circuited first. This is because a large, and potentially-dangerous, secondary voltage will appear across an open-circuited CT. Normally, a set of links is provided at those terminals for this purpose.
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.
What happens when secondary of the transformer is open?
The secondary winding leakage inductance limits the current during a short. It seems that the current through the primary is limited by winding resistance and leakage resistance when the secondary is shorted.
How does a current transformer work?
A current transformer is used in high voltage circuits where it is not possible to measure current directly. A CT is a step up transformer with only one turn in primary. There will be as many cores based on the purposes like metering, protection etc. The secondary of a CT should never be kept open circuited bcoz very high flux will be developed in the secondary and hence it may be damaged.
What precaution should be taken when working with current transformer that is in service?
Its secondary must never be open circuited. If its burden is to be removed, then the secondary must be short circuited first, and removed only after the burden is replaced.
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 current transformers be shunted before opening the secondary winding?
A current transformer's secondary must never be open-circuited. If the instrument fed by a CT needs to be removed, then the secondary terminals must be short-circuited first. This is because a large, and potentially-dangerous, secondary voltage will appear across an open-circuited CT. Normally, a set of links is provided at those terminals for this purpose.
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.
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.
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?"
Why current transformer is step down transformer?
Current transformers ('CTs') are used in high-voltage systems to allow the currents flowing in these systems to be measured or to operate protective systems. A CT's secondary winding is isolated from the high-voltage system, allowing measurements to be made, or protective devices to operate, safely.Actually, a CT is a 'step up' transformer, because the terms 'step up' and 'step down', refer to voltages, not currents. For this reason, a CT should NEVER be allowed to have its secondary winding open circuited.
Why current transformer secondary side short circuit?
A current transformer (or CT) is constructed in a specific way so as to step down the current in a high power circuit for measuring or protective relaying purposes. Typically, it will have a toroidal-shaped iron core with the secondary windings wrapped around it. the primary "winding" is usually the conductor of the main power system passing directly through the hole in the center of the CT. As a result of this construction, if the secondary windings are left open, a very large flux can develop, resulting in damage to the CT and possibly even the other equipment it is attached to. As such, if the CT is not going to be used, its secondary windings need to be shorted.
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 happens when secondary of the transformer is open?
The secondary winding leakage inductance limits the current during a short. It seems that the current through the primary is limited by winding resistance and leakage resistance when the secondary is shorted.
