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Why does transformer draws current when secondary is kept open?

Anonymous

∙ 14y ago

Updated: 4/28/2022

A: If the transformer is connected to a power input of course it will draw current. The primary is a long wire it has own resistance wrap around an iron core. Of course there will be primary current whether there is a load on the secondary or not.

Wiki User

∙ 14y ago

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Q: Why does transformer draws current when secondary is kept open?

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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.

Why leakage reactance is kept small?

Leakage reactance is useful for limiting the short circuit current in transformer and generators. therefore normally the reactance of transformer varies for 4.5% for distribution transformer to 12.5% for 400KV class.

Why rating if transformer is taken in KVA?

Unit or say Rating of transformer is in KVA and not in KW because copper loss of a transformer depends on current and iron loss on voltage. Hence, Total transformer loss depends on volt-ampere ( VA ) and not on phase angle between voltage and current i.e. it is independent of load power factor. That is why Unit or say Rating Of Transformer Is In KVA and not in KW.

What happen if 440V is connected to 220V transformer?

If the frequency is kept the same, you will overexcite the transformer, and it will draw excessive current (similar to inrush currents). Insulation tests are performed on transformers above nominal voltage, but they are performed at higher than rated frequency to keep the volts per hertz roughly equal to prevent overexciting the core.

Why the transformer is kept at a height from the ground?

If you are referring to a pole-mounted distribution transformer, it's in order to maintain a safe clearance between its high-voltage connections and ground level.

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Related Questions

Why do secondaries kept short in current transformer?

To prevent the appearance of a dangerously-high secondary voltage across its terminals.

Why keep a voltage transformer secondary open?

it is keep open so as to supply voltage to the loadAnswerThe secondary winding of a transformer is NOT necessarily kept open, unless you want to disconnect its load.

What are the precautions using current transformer and potential transformer?

Secondry of CT should never kept open during functioning

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.

Why transformer rating is in kva?

major losses in the transformer in the volt-ampers.AnswerA transformer's iron losses depend on the magnitude of the flux which, in turn, is proportional to voltage, while its copper losses depend on the winding currents. As both iron and copper losses contribute to the maximum operating temperature of the transformer, it follows that a transformer must be rated in terms of voltage and current. In alternating current systems, the product of voltage and current is apparent power, expressed in volt amperes.As a transformer's secondary voltage is kept approximately constant, it is its 'volt ampere' rating that determines its maximum (secondary) load current.Expressing a transformer's rating in watts (i.e. true power) would be completely meaningless because, with a highly-reactive load, it will be supplying practically zero watts while still possibly having to supply its rated current.

Does a transformer changes the frequency of incoming supply?

Yes the transformer effects the incoming frequency supply. This frequency is dependent on the core lamination of the transformer the weightier the core lamination the lesser will be the frequency we get and vice verse..

Why is the rating of transformer in kVA?

kVA is essentially power rating (capacity) of a transformer. Since power is equal P=I*V, so P=kV*A, with I measure in Amps or denoted as A.AnswerA transformer's iron losses depend on the magnitude of the flux which, in turn, is proportional to voltage, while its copper losses depend on the winding currents. As both iron and copper losses contribute to the maximum operating temperature of the transformer, it follows that a transformer must be rated in terms of voltage and current. In alternating current systems, the product of voltage and current is apparent power, expressed in volt amperes.As a transformer's secondary voltage is kept approximately constant, it is its 'volt ampere' rating that determines its maximum (secondary) load current.Expressing a transformer's rating in watts (i.e. true power) would be completely meaningless because, with a highly-reactive load, it will be supplying practically zero watts while still having to supply its rated current.

Why leakage reactance is kept small?

Leakage reactance is useful for limiting the short circuit current in transformer and generators. therefore normally the reactance of transformer varies for 4.5% for distribution transformer to 12.5% for 400KV class.

What happend if secondry is kept open in Current transformer?

A CT attempts to push a specific ratio of primary current through the secondary. If the secondary burden is a very high resistance (as in an open circuit), the voltage developped across the secondary will build up until it reaches the theoretical limit of the primary voltage. Before it gets to this voltage, it will arc across the air gap in the secondary open (often between two terminal blocks). As an old tech once told me, you only open the secondary of a CT once...the arcs can be fairly spectacular.

Why rating if transformer is taken in KVA?

Unit or say Rating of transformer is in KVA and not in KW because copper loss of a transformer depends on current and iron loss on voltage. Hence, Total transformer loss depends on volt-ampere ( VA ) and not on phase angle between voltage and current i.e. it is independent of load power factor. That is why Unit or say Rating Of Transformer Is In KVA and not in KW.

How much water will absorb transformer oil if 500 kva Transformer oil is kept exposed to moiasture?

none

What happen if 440V is connected to 220V transformer?

If the frequency is kept the same, you will overexcite the transformer, and it will draw excessive current (similar to inrush currents). Insulation tests are performed on transformers above nominal voltage, but they are performed at higher than rated frequency to keep the volts per hertz roughly equal to prevent overexciting the core.

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