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Current Transformers produce a ratio of primary current in the secondary. If the secondary of a CT is open circuited, and primary current is flowing, the CT will try to push that same ratio of current through the secondary open circuit. This causes secondary voltage to climb until it the secondary open circuit flashes over. This can often damage the CT.
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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 secondary windings of current transformers are shorted?
Current transformers (CTs) -together with voltage (or potential) transformers- are 'instrument transformers'. CTs are used to enable large currents flowing in high-voltage systems to be measured, while electrically-isolating the ammeter (termed a 'burden') from the h.v. system. They are also used to monitor h.v. currents for high-voltage protection systems. Before disconnecting its burden, the secondary of a CT must be short-circuited, and remain short-circuited until after the burden has been replaced. This is because a dangerously-high voltage will appear across the open terminals of any energised CT.
Is it necessary to connect a fuse at the secondary side of a current transformer?
Definitely NOT! An open circuit (across a melted fuse for example) on the secondary side of a current transformer is subject to a dangerously-high voltage, so a fuse must not be fitted. The secondary side of a CT must never be open circuited.
What happens when the primary winding is energized and the secondary winding is open circuited?
A voltage appears between the terminal points of the secondary winding
Why must a fuse or Switch never be fitted to the secondary of a CT circuit?
Secondary of a CT should never be opened to avoid damage to CT. Fuse or switch may lead to opening of CT secondary accidentally.
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 secondary coil of ct is short?
A CT attempts to push a specific ratio of primary current through the secondary. If the secondary is open circuited, the resistance across the secondary will be very large. Following Ohm's law, V = I*R, so the secondary voltage will become very large, and will arc across the open, or damage the CT, or both.
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.
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.
How do you disconnect ammeter from current transformer?
A CT's secondary winding must never be open circuited as it may provide a shock hazard to the user. The terminals to which an ammeter is connected to a CT is normally provided with a set of links that must be closed, short-circuiting the CT, beforethe ammeter can be removed. The ammeter must the be reinstalled before the shorting links are reopened.
Why secondary windings of current transformers are shorted?
Current transformers (CTs) -together with voltage (or potential) transformers- are 'instrument transformers'. CTs are used to enable large currents flowing in high-voltage systems to be measured, while electrically-isolating the ammeter (termed a 'burden') from the h.v. system. They are also used to monitor h.v. currents for high-voltage protection systems. Before disconnecting its burden, the secondary of a CT must be short-circuited, and remain short-circuited until after the burden has been replaced. This is because a dangerously-high voltage will appear across the open terminals of any energised CT.
Why is current maximum when short circuited?
when its is short circuited there will not be any drop and hence the current will b maximum when its is short circuited there will not be any drop and hence the current will b maximum
Why induction motor is also called short circuit transformer?
Like transformer induction motor has stator winding(Primary winding) and rotor winding(Secondary winding) separated by an airgap.Rotor winding(generally Al bars) are short circuited at the end to produce torque for the rotation.Hence the name short circuited transformer.
Is it necessary to connect a fuse at the secondary side of a current transformer?
Definitely NOT! An open circuit (across a melted fuse for example) on the secondary side of a current transformer is subject to a dangerously-high voltage, so a fuse must not be fitted. The secondary side of a CT must never be open circuited.
Why potential transformers are open circuited?
Beacause CT is shorted so it is kept opened
Why current transformers secondary is always short circuited?
Unless a burden (i.e. meters, relays, etc.) is connected to the CT, current transformers should always be shorted across the secondary terminals. The reason is very high voltages will be induced at the terminals. Think of the CT as a transformer, with a 1 turn primary and many turns on the secondary. When current is flowing through the primary, the resulting voltage induced in the secondary can be quite high, on the order of kilovolts. When a CT fails under open circuit conditions, the cause of failure is insulation breakdown, either at the shorting terminal strip, or at the feedthrough (in the case of oil filled apparatus), because the distances between terminals are not sufficient for the voltages present.
How do you get an iPhone that has short circuited?
Go to an ATT store, buy an iPhone, take it home and power it on. Then drop it in the toilet. There you go. iPhone that is short circuited.
