# Identifying the winding that has multiple taps?

• danilorj
In summary: , in summary, if you have a transformer with multiple taps, you can identify it by measuring the resistance between all taps and the common tap.

#### danilorj

hi guys
Do you know a way of identifying the winding that has multiple taps?
Do you know some material on internet that explain this better?

This is about transformers?

Suppose you had a transformer with multiple primary taps so that it could be used on different mains input voltages.
It might have a single 15 volt secondary winding. This will normally be wound with thicker wire than the primary.

The transformer will work backwards. That is, if you feed 15 volts AC into the thicker winding from some other transformer or power source, then the primary will develop voltages that are similar to the intended input voltages. They may not be exactly right, but they could be close enough to let you estimate what the transformer was for.

If you only had 6 volts AC and the thick winding was not labelled, you could still try it and get an idea of the type of primary winding on the transformer.

For example, you might get 55 V, 60 V and 65 V. If you lived in America, you would suspect that this transformer was intended to give about 12 volts out and these were primary taps for 110 volts +/- 10 volts.

If it was a discarded transformer and didn't smell like burnt paint, you could just try it with 110 volts on the primary. Nothing to lose and you might find a useful transformer.

Be careful with high voltages.

Another note - transformer designers usually wind the primary first. I think it's because it eases the burden of laying down multiple secondary's. In any case, it seems to have become a tradition.

The primary winding / windings will always have a hefty bit of insulation between it / them and the secondaries. Many transformers were wound with two primaries - each for 115 volt. When used in the USA, they are wired in parallel. In Europe, they are wired in series for 230V.

PS - A 100W lamp in wired series might keep you from a disaster and allow you to measure the relative voltage of the windings

Careful measurement of the dc resistance between the common and the individual taps will determine the sequence of the taps and relative number of turns between taps.

Bob S

Bob S,
I want to know I way of identify a winding that has multiple taps.
If this way is visual or if I can do an essay to find it.

danilorj said:
Bob S,
I want to know I way of identify a winding that has multiple taps.
If this way is visual or if I can do an essay to find it.
Find all the taps on a transformer coil that have a finite (low) common resistance. Very carefully measure the resistance (using milliohm scale if necessary) between all taps and the common tap, and deduce the sequence of taps on the winding (more resistance means more turns) based on the relative resistances.

Bob S

## What is the purpose of identifying the winding that has multiple taps?

Identifying the winding that has multiple taps is important in order to determine the proper connections for the transformer and ensure the correct voltage and current levels.

## How can I identify which winding has multiple taps?

The winding with multiple taps can be identified by checking the transformer's specifications or by physically inspecting the transformer for multiple tap leads.

## What are some common signs that a winding may have multiple taps?

Some common signs that a winding may have multiple taps include multiple tap leads, a tap changer switch, or a tap changer handle on the transformer.

## Can I use a multimeter to identify the winding with multiple taps?

Yes, a multimeter can be used to identify the winding with multiple taps by testing the resistance between different tap leads. The winding with multiple taps will have varying resistance values.

## How do I make sure I am connecting the winding with multiple taps correctly?

To ensure correct connection of the winding with multiple taps, refer to the transformer's specifications or consult an expert in transformer connections. It is important to make sure the tap leads are connected in the correct sequence to achieve the desired voltage and current levels.

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