Transformer Open and Short Circuit Test for the CBT Electrical Power PE Exam (Electrical PE Review)

[@electricalpereview]

Video Table of Contents (Click the time stamp to advance): 0:00 - Problem introduction 2:21 - Open circuit voltage (Vo), power (Po), and current (Io) 3:54 - Open circuit power factor (θo) 5:00 - Solving for the core resistance current (Ic) 6:04 - Solving for the core resistance (Rc) 7:30 - Solving for the magnetizing core current (Im) 12:14 - Solving for the magnetizing reactance (Xm) 15:21 - Solving for the open circuit power (Po) 16:53 - Short circuit test basics and introduction 19:07 - Solving for the equivalent series winding resistance (Req) 21:26 - Solving for the magnitude of the series winding impedance |Zeq| 22:41 - Solving for the equivalent series leakage reactance (Xeq) 24:30 - Calculating transformer percent impedance (%Z) from the short circuit test Come learn why we are the fastest growing PE exam prep service provider for the new CBT format of the Electrical Power PE Exam at www.electricalpereview.com

[@md.arifulislam3616]

thank you for this video.

[@kasunsalu5792]

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[@engineerx3482]

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[@md.monzurhassan5163]

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[@md.arifulislam780]

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[@wickedpawn5437]

You didn't refer the equivalent circuit to the primary as the problem stated.

[@electricalpereview]

The circuit parameters solved for in the video are already referred to primary, no other step is needed since they were solved for using the open circuit and short circuit test values that were applied and measured at the primary terminals.

[@wickedpawn5437]

Thanks for the clarification. I missed that the primary is 120V and the secondary is 240V. You tend to think that the primary is always the high voltage side.

[@binwenyan8626]

Amazing Video!!Very helpful! I sign up your class 2019 but did not take the exam, I plan to take the exam next month, wondering should I sign up the class again, is there going to be a lot of changes on the classes as it is CBT now?

[@electricalpereview]

Glad you enjoyed the video. We updated 100% of our live class material to match the new CBT specifications starting August 2020 when the change to the CBT exam was first announced and was one of the first providers to do so.

[@md.arifulislam3616]

good information

[@jaymoseley6216]

If an apparent power rating was supplied, why wouldn't you be able to change the impedance values already found into per unit to get %z? Or start by changing the SC current and voltage values into PU values then determine the %z from there. Shouldn't vpu/Ipu = zpu regardless of whether or not Ipu happens to equal 1 because its' at rated load?

[@electricalpereview]

Hi Jay, if the power rating of the transformer is given, then yes you can absolutely use this value along with the voltage rating to calculate the base impedance of the transformer and convert the calculated impedance from the short circuit test to percent impedance. In this particular example, the power rating of the transformer is not given. Using the power rating of the transformer would also allow us to calculate the base impedance in order to use Ohm's law for the per unit impedance (vpu/Ipu = zpu).

[@jaymoseley6216]

@@electricalpereview I may have misunderstood what you saying towards the end. I really appreciate the free content you put out there. It is well presented and easy to understand. I watched your 2 equation sheet reviews the night before my exam and it was a great refresher to get myself thinking about all of the potential problems I may encounter and everything I had studied for 4 months.

[@electricalpereview]

@@jaymoseley6216 Glad to hear it. We have more free study material available in the free trial on our website at www.electricalpereview.com

[@rubelapon8114]

Nice

[@aminulmizi6275]

do you need to apply the turns ratio to the current on the secondary side short circuit current to get I2 or is it the same?

[@electricalpereview]

Hi Aminul, yes, during the short circuit test you can use the transformer ratio to step up or down the current between the primary and secondary side just like you would during normal conditions.

[@mstrasma8323]

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[@md.arifulislam780]

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