Typical X/R ratio for transformer and induction motor

[Siyou]

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!

 

[xnuke]

X/R values vary depending on construction, so the graph offers you an envelope within which they normally will fall.

 

[7anoter4]

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.

 

[Siyou]

@ 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.

 

[waross]

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

 

[Siyou]

How did ETAP solve for the device capability of the momentary and interrupting summary report?

Thank You