Transformers - Short Circuits and Open Circuits

hello dear friend,

Sort circuit test sort secondary side measure input voltage and current

Open circuit test open secondary side and measure input voltage and current

little bit of i know about transformer

thank you

rajaramang1984

Quite a good information in these links (from Google search):

http://www.energymanagertraining.com/power_plants/Transformers.htm

http://claymore.engineer.gvsu.edu/~johnsodw/egr325mine/paper2/paper2.html

http://www.ece.vt.edu/ece3354/labs/TEQ_review.pdf

I am sure, it will help you.

-MS

CR4 Admin: removed broken lilnks

but these are based on 1ph transformer.can you find any 3ph power transformer testing reference?

I have prepared 3 phase system block diagram for you. To Test the 3 phase transformer, you need

(1) One 3 phase variable power supply

(2) Two Wattmeters

(3) Three ammeters

Always, you can consider the low voltage side as primary for this test

thanks a lot. but i have 100MVA,220/34.5 KV transformer. so,i think it will req. PT and CT also. to measure the high voltage/currents.

This wroung information. please do not enter any thing with flectuation.

rajaramang1984 is somehow right, but need something more.

For the short circuit test need to short the secondary and apply voltage in the primary so that you get rated current in the secondary. Then measure the voltage and current in the primary. The short circuit test determines the losses in windings, which are dependent on the current- the reason you need to have rated current in the secondary.

For the open circuit test, leave the secondary windings open and apply rated voltage at the primary winding, then measure the current, wich is the iddling current, the voltage; with a power meter you can measure directly the power losses, active and reactive. The open circuit test determines the core losses.

testing in 1ph transformer have given in all books/refernce.please give any reference for 3ph power transformer testing ?

Well, the three phase is an extrapolation of the one phase, when it comes to measuring. perhaps you heard about Blondel, a guy who discovered that if you measure the power consumed, on each phase, and add the values together you get the power consumed in that three phase system. The references are generally given for 1 phase; the three phase system is designed to work even on all three phases; by passing from 1ph to 3ph just need to add another 2 phases, and the equipment for each of them, even when measuring voltage, current, power, energy, power factor.

If a text says about a 3ph system and the drawings only show a 1 ph system it means you should keep in mind that there are another 2 ph along with that drawing.

Don't get lost in those details. Someone must have told you this stuff before you graduated the engineering school. Or not. How did you get there working with 100MVA transformers and not knowing basic things about three phase system? I'm asking this because this is about all there is about the 3ph system- 3 wires-all equiped almost the same.

Losses in transformer windings have 2 components: one part due to the (reactive) power requirements for magnetization of the circuit and one part due to how much you load the transformer.

The first part is nearly constant irrespective of the load and is often called no-load losses.

The second is dependent on the transformer load and varies from (basically) 0 to max (full load).

As mentioned before, the open circuit test is performed with the secondary side open (2 tests, primary and secondary swapped). This allows to determine the resistance of the winding and subsequently the corresponding losses.

The short circuit is performed (as shown earlier) with the secondaries short-circuited, applying a primary voltage up to a level that the secondary current equals the rated secondary current.

Since in a short circuit operation the power factor is very low, usually the resistance component can be neglected so that the measured values apply only to the inductive impedance of the winding.

Open circuit test:

Open circuit test is doing on the Low Voltage side by keeping the High Voltage side open, Apply rated Voltage in Low voltage side, the wattmeter connected in the supply side gives noload losses which is approxi. equal to Core loss.

SHort circuit test is doing in the high voltage side by keeping the low voltage side shortcircuted. Apply Voltage to a high voltage side such that ammeter connected in that side shows rated amp. (rated amp=100e6/34.5e3) The wattmeter connected in the high voltage side shows Short circuit loss. Which is approximately equal to the Copper losses.

I think it is clear for u

shinerajcet@gmail.com

Open circuit, no current flow and the voltage tends to the electromagnetic field of what generating the voltage. When circuit is open there is no voltage drop across the internal resistance so true internal emf seen. In short circuit where the voltage tends to zero and current tends to infinity. if switch is off site, will be an open circuit between its two contacts and if switch is onsite there will be short circuit between two contacts.