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Typical X/R ratio for transformer and induction motor

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Siyou

Electrical
Joined
Jul 12, 2020
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30
Location
PH
Hello everyone!

Can I ask what is the meaning of low, medium, and high on the graph of the typical X/R ratio of transformer and induction motor in IEEE standards?

Attached here is the picture of the typical X/R ratio.

Thanks everyone!
 
 https://files.engineering.com/getfile.aspx?folder=f920fe84-a213-4b09-a39f-cd49a482d410&file=Transformer.JPG
X/R values vary depending on construction, so the graph offers you an envelope within which they normally will fall.
 
This diagram is from ANSI - IEEE C37.010 Application guide for ac high-voltage circuit breakers rated on a symmetrical current basis, in order to facilitate short-circuit calculation for circuit breaker ratings.
 
 https://files.engineering.com/getfile.aspx?folder=6823dbdf-428f-4adc-b040-deb504f155b9&file=IMPEDANCE_AND_X_R.pdf
@ Xnuke so what will I use? low, medium or high? The low, medium and high graph has its own X/R values.
I dont have the data of the X/R ratio of transformer and induction motors for my short circuit calculation, thats why I will be using the typical values from IEEE standards, but sadly the low, medium and high graph has no meaning if what does this low, medium and high are for.
 
OP said:
I dont have the data of the X/R ratio of transformer and induction motors for my short circuit calculation,
Use the impedance voltage to calculate the symmetrical short circuit current.
Use this value to match switch-gear ratings.
For mechanical forces on supports, the worst case, 100% offset, asymmetrical current will approach 2.83 times the symmetrical short circuit current. (2 x Root 2)


Bill
--------------------
"Why not the best?"
Jimmy Carter
 
How did ETAP solve for the device capability of the momentary and interrupting summary report?

Thank You
 
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