Single phase hand cranked transformer turns ratio tester

  • Used for testing single phase power and distribution transformers
  • Design based on precision bridge measuring technique
  • Unmatched accuracy (±0.1%) in a portable design

The Single Phase TTR, Transformer Turns Ratio Test Set, measures the turns ratio and exciting current of windings in power, potential and current transformers. Deviations in turns ratio readings indicate problems in one or both windings or the magnetic core circuit.

The TTR test set aids in identifying:

  • Shorted coils
  • Open circuits
  • Incorrect connections
  • Internal faults or tap-changer defects in step regulators as well as in transformers

The instrument measures highly sensitive turns ratios of up to 129.99:1 with accuracy of ±0.1%. An optional auxilary transformer extends the ratio range to 329.99:1.

The TTR set operates on the principle that the voltage ratio of the transformer at no load is practically equal to the true turns ratio.

The major source of error in a transformer is a primary impedance drop due to magnetizing current, which is kept to a minimum by excitation at a fraction of rated voltage. By employing a design that meets both of these conditions along with the use of a null balance system, the turns ratio of a transformer can be determined accurately.

When measuring the turns ratio of distribution and power transformers, the accuracy is well within 0.1%.

TTR 550503

TTR 550503 Firmware Update


Firmware version 6.5 is available via Megger’s repair department as part of a hardware update and will not appear on this website. Both Firmware versions 6.4 & 6.5 improve reliability, but 6.5 improves reliability drastically and completes tests in half the time.

The hardware update related to Firmware version 6.5 will be performed FREE OF CHARGE (this does not include cost of shipping to and from Megger factory or Megger Authorized Service Center [ASC]).

Please note: Any required hardware repairs not related to Firmware version 6.5 will incur standard repair charges.

Please contact your nearest Megger sales representative for information on where to return your instrument for updates.

The Megger Valley Forge, USA factory and select Megger ASCs can perform updates. If you do not feel capable of performing updates properly, please contact your nearest Megger sales representative for information on where to return your instrument for updates.

Carefully read all instructions and backup your data before performing any updates.

Only update the firmware or software if you are experiencing difficulty with your instrument or if you have a specific need to do so.


Incorrect installation of updates and incomplete updates may cause an error and make the equipment unusable.

If damage occurs from improper updates, customer is responsible for repair costs.

1. PowerDB PC Upgrade [Optional]:

a. Download PowerDB 11 (You will be redirected to

b. TTR PC Quick Manual

2. Install TTR 550503 Firmware Upgrade:

Please refer to the version on your TTR 550503 Self-Test screen during startup to determine if this update applies to you

a. TTR 550503 Firmware Upgrade Instructions

b. Download TTR 550503 Firmware Upgrade Installer - Firmware version 6.4

c. TTR 550503 Quick Manual

TTR 550503 Firmware Upgrade Installer
97.2 KB | 10/12/21
TTR 550503 Firmware Upgrade Instructions
257.2 KB | 10/12/21
TTR 550503 Quick Manual
537.6 KB | 10/12/21
TTR PC Quick Manual
561.7 KB | 10/12/21