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What is percentage impedance?

Updated: 8/11/2023
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9y ago

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In electrical engineering, the percentage impedance of a transformer is the voltage drop on a full load, which is expressed as a percentage of the specified rated voltage. It's measured by conducting a short circuit test.

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9y ago
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14y ago

The percent impedance you're referring to is used in symmetrical components, and the reason for using symmetrical components is the same reason to discuss transformer impedance in this way. If not discussed in this fashion, you must use two impedance values - one for the high side, and one for the low side - for a two winding transformer.

From the highside of the transformer, there's a higher voltage, V1 than on the lowside V2. Also, there is a lower current I1 than on the lowside I2. This is because power will remain constant through the transformer. Impedance = Voltage / current, so you can see that V1/ I1 will be different than V2/I2.

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12y ago

The term, percentage impedance, is somewhat misleading. Percentage impedance is defined as the percentage of the rated primary voltage required to cause a rated secondary current to flow when the secondary is short circuited. Percentage impedance is used to determine how a transformer limits a short-circuit fault current.

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If impedance of power transformer is increase from 8 to 10 percentage then what will effect?

if the designed value of percentage impedance is change, for general this should affect tow things * if the percentage impedance is decrease this should increase the fualt level current *if the percentage impedance is increase this should increase the transformer losses and tempreture rise so the designed value of percentage impedance is determined according IEC if it is less than or equal 10% the margin should be + or_ 15%, if it is more than 10% the margin should be + or _ 15% so the percentage impedance of this transformer is not accepted according IEC standers


The purpose of transformer percentage impedance?

Inherently, the actual impedance seen at the secondary voltage will be different than that seen at the primary voltage. To make things easy, we use symmetrical components, where transformers are reduced to a p.u. (per unit) impedance. 100 x p.u. is equivalent to the percentage impedance you are referring to. When converted to per unit, a transformer has one impedance, not two, so it does not matter whether you are looking through the transformer from the secondary or the primary.


HOW TO CALCULATE THE IMPEDANCE FOR THE TRANSFORMER?

The term, 'percentage impedance', is a little misleading, as it is defined as 'the value of primary voltage that will cause rated current to flow in the secondary winding, expressed as a percentage of the rated primary voltage'. So, the test is carried out as follows: the secondary winding is short-circuited through an ammeter capable of reading the rated secondary current. A variable voltage is applied to the primary winding. The primary voltage is gradually increased until the ammeter indicates rated secondary current. That primary voltage is then expressed as a percentage of the rated primary voltage -and that value is the transformer's 'percentage impedance'.


Which is better high input impedance or low input impedance and why?

That depends on the output impedance. In electronic we use voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is more than ten times higher then the output impedance. An input impedance is called also a load impedance or an external impedance. An output impedance is called also a source impedance or an internal impedance.


How to distinguish between characteristic impedance and input impedance?

The characteristic impedance or surge impedance belongs to uniform transmission lines.In electronic gears we use voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is more than ten times higher then the output impedance.An input impedance is called also a load impedance or an external impedance.An output impedance is called also a source impedance or an internal impedance.

Related questions

If impedance of power transformer is increase from 8 to 10 percentage then what will effect?

if the designed value of percentage impedance is change, for general this should affect tow things * if the percentage impedance is decrease this should increase the fualt level current *if the percentage impedance is increase this should increase the transformer losses and tempreture rise so the designed value of percentage impedance is determined according IEC if it is less than or equal 10% the margin should be + or_ 15%, if it is more than 10% the margin should be + or _ 15% so the percentage impedance of this transformer is not accepted according IEC standers


The purpose of transformer percentage impedance?

Inherently, the actual impedance seen at the secondary voltage will be different than that seen at the primary voltage. To make things easy, we use symmetrical components, where transformers are reduced to a p.u. (per unit) impedance. 100 x p.u. is equivalent to the percentage impedance you are referring to. When converted to per unit, a transformer has one impedance, not two, so it does not matter whether you are looking through the transformer from the secondary or the primary.


What is percent impedance?

The percentage impedance of a transformer is the volt drop on full load due to the winding resistance and leakage reactance expressed as a percentage of the rated voltage.It is also the percentage of the normal terminal voltage required to circulate full-load current under short circuit conditionsThe impedance is measured by means of a short circuit test. With one winding shorted, a voltage at the rated frequency is applied to the other winding sufficient to circulate full load currentZ% = Impedance Voltage x 100Rated Voltage


HOW TO CALCULATE THE IMPEDANCE FOR THE TRANSFORMER?

The term, 'percentage impedance', is a little misleading, as it is defined as 'the value of primary voltage that will cause rated current to flow in the secondary winding, expressed as a percentage of the rated primary voltage'. So, the test is carried out as follows: the secondary winding is short-circuited through an ammeter capable of reading the rated secondary current. A variable voltage is applied to the primary winding. The primary voltage is gradually increased until the ammeter indicates rated secondary current. That primary voltage is then expressed as a percentage of the rated primary voltage -and that value is the transformer's 'percentage impedance'.


Which is better high input impedance or low input impedance and why?

That depends on the output impedance. In electronic we use voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is more than ten times higher then the output impedance. An input impedance is called also a load impedance or an external impedance. An output impedance is called also a source impedance or an internal impedance.


How to distinguish between characteristic impedance and input impedance?

The characteristic impedance or surge impedance belongs to uniform transmission lines.In electronic gears we use voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is more than ten times higher then the output impedance.An input impedance is called also a load impedance or an external impedance.An output impedance is called also a source impedance or an internal impedance.


Input impedance is greater than to load impedance?

In electronic gears we use voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is more than ten times higher then the output impedance.An input impedance is called also a load impedance or an external impedance.An output impedance is called also a source impedance or an internal impedance.


Is characteristics impedance of a filter is same as output or load impedance?

load impedance


What is analog audio impedance?

To get all the audio voltage from a source to a target without loss you need voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is at least ten times higher then the output impedance.An input impedance is called also a load impedance or an external impedance.An output impedance is called also a source impedance or an internal impedance.


What is high input impedance?

To get all the voltage from a source to a target without loss you need voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is more than ten times higher then the output impedance.An input impedance is called also a load impedance or an external impedance.An output impedance is called also a source impedance or an internal impedance.


In a multistage amplifier input impedance is high and output impedance is low justify the statement?

no. input impedance is low & output impedance is high


Input impedance is high and output impedance is low justify the statement?

To get all the voltage from a source to a target without loss you need voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is more than ten times higher then the output impedance.An input impedance is called also a load impedance or an external impedance.An output impedance is called also a source impedance or an internal impedance.