Raytech USA, Inc. All rights reserved
Ver. 1.13
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TRANSFORMER TURNS RATIO TESTING
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A Transformer Turns Ratiometer does exactly as its name implies; it is used primarily for checking how many
Turns of wire are in the primary side and the secondary side of a transformer. The Turns Ratio test set does not tell
exactly how many turns of wire are in the primary and secondary coils. But rather, it measures and displays the
Ratio of (or comparison of) the number turns in the primary coil to the number of turns in the secondary coil.
This is an extremely useful device for checking for shorted turns and incorrect settings of tap changers.
It is important to understand that the Nameplate Ratio on most transformers is the Voltage ratio (Voltage in:
Voltage out) and this Ratio is determined, basically, by the number of turns of wire on the Primary (High side), the
number of turns of wire on the Secondary (Low Side).
On a single phase Transformer the Turns Ratio is the same as the Voltage Ratio.
A Single Phase transformer:
For example: The High Side Winding may contain 960 Turns : Low Side Winding 440 Turns.
Therefore:
Note: 3 Phase Transformers: Turns Ratio & Voltage Ratio are usually different.
IMPORTANT NOTE 1: Hooking up to a transformer:
The TR-1 & TR-1P protect against improper hook-up to a transformer or testing a severely defective transformer.
Every effort has been made to alert the operator when something is wrong. The test system senses when it is
connected to a transformer, and in most cases, in a proper manner. The test system will not start a test unless it is
connected to a transformer.
Transformer Turns Ratiometer uses:
Transformer Turns Ratiometer is very useful as a tool for investigating problems associated with the core, the
windings, and the tap changer of transformers and the Raytech TR-1 can be used for:
1. Identify shorted turns and finding turn errors
2. Checking continuity of connections on a transformer
3. Locating defective and incorrect tap settings
4. Defining mislabeled terminals and nameplates
Turns Ratio testing is a required test during the manufacture of transformers. Turns Ratio testing should be a part of
a good routine preventative maintenance program as well as for acceptance testing.
