Transformer Impedance for Dummies

Transformer resistance test

Weird: just yesterday we ran across a freelancer with a degree in earth science who didn't know basic geology. At the time, we said, "Few freelancers draw as much scorn from the Antisocial Network staffers as the ones who claim to have an educational background for their topic yet totally blow it when they start writing." Well, today's nominee is only a little different: they're Blake Flournoy, who wrote in a different Leaf Group bio that, "[T]hey made a name for themselves repairing appliances..." Based on what they wrote in the Sciencing.com post "How to Use an Ohmmeter to Test an AC Transformer," though, they didn't learn anything about transformers.

Flournoy's assignment was to rewrite an original by Alexander Rudinski, whose BS was in communications. Definitely a "BS," given that what Alex wrote was utter bull. You'd think that in the process of performing a rewrite, however, Blake would have corrected some of the misstatements and fixed the crap. But no: they merely freshened the prose a bit, leaving in such intellectual dross as,

• "Transformers are electrical devices used to transfer electrical energy between two or more circuits." – No, they're devices used to change voltage.
• "The resistance of an alternating current (AC) transformer is held within the wires wound around its core." – Lifted almost word for word from Rudinski... the resistance is a function of a) the natural resistance of the wire and b) any leakage due to failure of the insulation, short circuits, etc.
• "...a transformer... uses alternating current (AC) to increase or decrease the voltage of the electrical energy running through it..." – No, a transformer uses induction in accordance with Faraday's Law.
• "To test your transformer, simply touch the red and black pins of your ohmmeter to the opposite ends of the transformer's wiring." – Ummm, which are the "opposite ends"? Here, Blake, read this...
• "...compare the resistance on your ohmmeter to the resistance stated on the transformer's data sheet." – Just an FYI, Blake (and Alex): resistance transformer is calculated by measuring the voltage drop, not the absolute impedance. You then use Ohm's Law to calculate the resistance, which should be compared to the nominal Z% on the nameplate.

Apparently none of that made sense to Rudinski, and Flournoy didn't improve on the factual content of the post. Ergo, Blake's our Dumbass of the Day, rewrite division... again.

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