The Megger TTR20 is an automatic hand-held battery operated transformer turns ratio test set. It is used to measure the turns ratio, excitation current and polarity of windings in single- and three-phase distribution and power transformers (tested phase by phase), potential & current transformers, and tapped transformers.

The unique design of the TTR20 allows the user to operate the test set while holding it in one hand. It effectively eliminates the user from having to kneel or bend down to operate the instrument and speeds up testing time. Realizing the extreme environments in which the TTR20 must operate, special attention has been paid to making it extra rugged, with a high impact, shock resistant case, yet incredibly lightweight at a mere 870 g (1.9 lbs).

Its design makes this instrument well suited for use in a variety of harsh environments. The TTR20 is particularly suited for testing in substations, transformer-manufacturing environments, and meter shops. It features a high-contrast, backlit LCD screen which can be seen in bright or ambient light.

This unit measures a high turns ratio of 10,000:1 accurately with the lowest excitation voltage. The excellent repeatability of the TTR20 helps the users to determine the condition of transformers under test. It is designed for simple, one button operation with the measured results displayed directly on the easy to read LCD or printed to the optional printer. The TTR20 needs no additional software and comes ready to use complete out of the box.

APPLICATIONS
The proper operation of a transformer relies almost entirely on the electrical properties of its windings. To ensure continued proper operation, transformers are tested to verify that their electrical properties have not changed from design specifications. A TTR is an extremely useful instrument for testing transformer windings because it can help locate several types of problems within single- and three-phase transformers.

It it used to determine the no-load accuracy of CTs and PTs and also determine the need to further test faulty CTs and PTs. The TTR20 applies voltage to the high-voltage winding of a transformer and accurately measures the resulting voltage from the low voltage winding. The ratio of voltages is directly proportional to turns ratio. In addition, the unit measures excitation current and polarity.

TRANSFORMER TURNS RATIO
A Transformer Turns Ratio Test Set such as the TTR20 can directly measure the turns ratio of single-phase transformers as well as three-phase transformers. Deviations in these measurements will quickly indicate problems in transformer windings and in the magnetic core circuits. Transformer ratio can change due to several factors, including physical damage from faults, deteriorated insulation, contamination and shipping damage. If a transformer ratio deviates more than 0.5 percent from the rated voltage ratio, it may not operate reliably. To measure small ratio changes such as this, the accuracy of a Megger TTR20 is needed.

Transformer Polarity
Polarity of a distribution transformer becomes of interest in order to determine its proper connection within a power network. The Megger TTR20 will identify normal (in phase) and reverse polarity of the single-phase transformers.