Transformer Voltage Sag

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mbrooke

mbrooke

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Does anyone know of a graph or calculations that would show the voltage sag of a transformer as current is increased on the secondary above the full load rating?
 
That sounds like a variation on a transformer impedance question.

I just did a "transformer impedance" search and found myriad results you can use, like "calculator."
 
LarryFine said:
That sounds like a variation on a transformer impedance question.

I just did a "transformer impedance" search and found myriad results you can use, like "calculator."
Click to expand...

yup, correct :)

Basically I want to put a current value above the FLA in order to get a corresponding output voltage.

Reactance might make a difference though, but willing to learn.
 
210609-2048 EDT

mbrooke:

I really do not understand your question.

To a large extent a transformer can be viewed for most loads as a linear circuit. Because of heating there will be changes vs time.

.
 
gar said:
210609-2048 EDT

mbrooke:

I really do not understand your question.

To a large extent a transformer can be viewed for most loads as a linear circuit. Because of heating there will be changes vs time.

.
Click to expand...

The % voltage drop as a transformer is loaded above 100%. Ie assuming 1.0pu on the primary, the voltage decline on the terminals are current increases to 200%, 300%, 1000%, 5000% above the FLA.
 
210609-2235 EDT

mbrooke:

The power rating of a transformer is a power dissipation factor relative to temperature rise, and thus failure point. It has virtually nothing to do with internal impedance other than how resistance changes, and at very high temperature the effect on magnetic characteristics of the core. But insulation failure will probably occur before major changes in core characteristics.

Take some electrical engineering courses.

.
 
Mbrooke,

A little though experiment to confirm voltage drop is linear:. Consider how transformer impedance is measured, and how that value is used to calculate secondary short-circuit current. We could not do this if it was not linear.
 
gar said:
210609-2235 EDT

mbrooke:

The power rating of a transformer is a power dissipation factor relative to temperature rise, and thus failure point. It has virtually nothing to do with internal impedance other than how resistance changes, and at very high temperature the effect on magnetic characteristics of the core. But insulation failure will probably occur before major changes in core characteristics.

Take some electrical engineering courses.

.
Click to expand...


Right and right. However under fault conditions lasting a few seconds there should not be any thermal magnetic damage.

I am concerned with output terminal voltage as a means to obtain step touch potential.
 
electrofelon said:
Mbrooke,

A little though experiment to confirm voltage drop is linear:. Consider how transformer impedance is measured, and how that value is used to calculate secondary short-circuit current. We could not do this if it was not linear.
Click to expand...


If linear, I will go that route. Doing all the equations I admit this is rather easy, easier than I thought.
 
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