I have always used transformer impedance shown on the dataplate as the % of voltage loss used to make the transformation at the 100% rated current on the secondary.
Up until today, I believed that when the secondary current exceeded the 100% rating of the OA coil, the impedance grew exponentially.
Everything I find on the web agrees with the first statement. Impedance listed is the loss at 100% of transformer rating.
Impedance testing today suggest that impedance is linear.
Low voltage was connected to the primary bushings and controlled with a Variac autotransformer.
A voltmeter was connected to the H bushings to measure the voltage input to the high side coil. The secondary was shorted with 1AWG copper and an ammeter was on that shorting conductor.
Voltage was increased and recorded through 25, 50, 100, 150, 200 and 250 percent current rating.
The transformer used was a 2400/4160-120/240, 10kVA oil filled pole mount. Testing started with a TTR showing 10.004.
Is this a valid impedance test?
Up until today, I believed that when the secondary current exceeded the 100% rating of the OA coil, the impedance grew exponentially.
Everything I find on the web agrees with the first statement. Impedance listed is the loss at 100% of transformer rating.
Impedance testing today suggest that impedance is linear.
Low voltage was connected to the primary bushings and controlled with a Variac autotransformer.
A voltmeter was connected to the H bushings to measure the voltage input to the high side coil. The secondary was shorted with 1AWG copper and an ammeter was on that shorting conductor.
Voltage was increased and recorded through 25, 50, 100, 150, 200 and 250 percent current rating.
The transformer used was a 2400/4160-120/240, 10kVA oil filled pole mount. Testing started with a TTR showing 10.004.
Is this a valid impedance test?
