Methods for testing the polarity of a single-phase transformer??

Answer 1

Using just an AC volt meter...

Connect line end of the secondary to the energized primary (an autotransformer configuration). If the windings are in phase, the voltage will add. If the windings are out of phase, the voltage will subtract.

Read the voltage from neutral side of primary to open end of secondary.

Answer 2

A single phase transformer doesn't really have a "polarity", since it is an Alternating Current device each output terminal will be positive half the time and negative the other half. You do need to identify the primary and secondary terminals though. If they aren't marked (H1, H2 for the high voltage side, X1, X2 on the low voltage side) you can check easily enough with an ohm meter. The high voltage will have about twice the resistance of the low volts side (for a 2:1 step down transformer). Four times for a 4:1 and so on. If you can see the wires coming from the coils the high voltage side will be the smaller wire.

Answer 3

There is no specific polarity on any transformer because of alternating current but you can reference the phase between primary and secondary coil in two ways. One method is by tracing the direction of windings. The beginning of winding of the primary is the same phase with the beginning of the secondary, provided that they are wound in the same direction. the other method is to compare the phases of two windings by using oscilloscope.
In most cases, the transformer manufacturer will mark the terminals of the transformer to indicate the beginning of the coil windings which are used as common terminals.

There maybe other technique that I'm not aware of.

Answer 4

I assume you're trying to determine if the single-phase distribution transformer is additive or subtractive. Hopefully there is a nameplate on the device.

LV bushing X1 is "in phase" with HV bushing H1.

If the H1 and X1 are on the same side of the transformer, it is known as a subtractive transformer.

If H1 and X1 are on opposite sides of the transformer, it is referred to as an additive transformer.

I hesitate to give you testing directions because if you don't know what you're doing the tests could become lethal.

Please e-mail me with transformer details for more information.

Answer 5

You can run the transformer with the secondary side open circuited, and measure the voltage between one of the primary terminals and each of the secondary terminals. Depending on the turns ratio, you should be able to figure out if the terminals your are measuring are in phase.