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EuroSMC ETP-3 Winding Resistance Measurement Unit


The ETP-3 is designed to measure very low resistance values on transformer windings or on any load with strong inductive component. The unit applies the necessary DC current to magnetize the winding and stabilize the current, in order to provide an accurate, repeatable measurement.

The EPT-3 is a unit that automatically performs measurements in all types of power, distribution, or instrument transformers, as seen below:

  • Winding resistance value in single or three phases.
  • Automatic correction of the resistance per phase to a predetermined reference temperature.
  • Automatic calculus of the compound winding resistance, for different configurations, Delta, Star, etc.

The software takes into account the connection group and the temperature to calculate simple (u, v, w) and compound (uv, uw, vw) ohmic resistance values referenced to a normalized temperature (temperature-corrected). The ohmic values obtained allow verifying the correct insulation between turns, and to assess the transformer’s specified electrical and mechanical characteristics.


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SKU: EuroSMC ETP-3 Category: Tag:

The following problems can be detected with the ETP-3:

  • Loose connections.
  • Tap changer malfunction.
  • Shorted turns.
  • Hot spots on the windings.

  • Performs the measurement of each phase, sequentially, without any change in the connection to the transformer, for each tap change position.
  • Uses a four-wire measuring method to avoid any error from the connection cables.
  • Automatic magnetization and de-magnetization of the iron core. This assures the accuracy and the repeatability of the resistance measurement and also the safety of the operator and the measuring unit in case of a sudden disconnection of the test leads.
  • Auto rang from 1 to 1kΩ. The test current range 5mA to 20A is automatically selected.
  • Automatic calculus of the resistance per phase.
  • The measured value is not affected by temperature variation or/and changes in the test current.
  • High immunity to external perturbations.


  • Quality Control after the manufacturing process.
  • Reception of new or repaired transformers.
  • Detection of possible problems during the maintenance task itself.
  • Integrates the data inside a predictive maintenance program.

The ETP-3 software selects the most suitable magnetization current range available and assures that the reading of the resistance value is always made with the same magnetization condition. This assures the validity of these measured values. Once the measurement is finished, the software does not allow to end the test until the iron core is completely demagnetized. The following types of voltage transformers can be tested with the ETP-3, despite the size and power:

  • Power Transformers (single or three phase).
  • Distribution Transformers (single or three phase).
  • Power Auto-transformers (single or three phase).
  • Instrument Voltage Transformers.
  • Current Transformers.
Test Signal Voltage: 24 Volts DC max.
Current: 0 to 20A ±5%
Measurement Ranges
Current Range Accuracy Resolution
20A 10mΩ ±0.5% of rdg. ±2 digits 1µΩ 4 digits
20A 100mΩ ±0.5% of rdg. ±2 digits 10µΩ 4 digits
5A ±0.5% of rdg. ±2 digits 100µΩ 4 digits
500mA 10Ω ±0.5% of rdg. ±2 digits 1mΩ 4 digits
50mA 100Ω ±0.5% of rdg. ±2 digits 10mΩ 4 digits
5mA 1000Ω ±0.5% of rdg. ±2 digits 100Ω 4 digits
Measurement Modes Manual: The user stops the test when the Reading is accepted as reliable.
Automatic: The software determines when to finalise the measurement.
By Phase: Allows accelerating the measurement on transformers greater than 100MVA
Used Parameters Compound winding resistance
Simple winding resistance
Temperature corrected
General Specifications
Power Supply 115V ±10% 50/60Hz (specify); 230V ±10% 50/60Hz (specify) (450VA max.)
Working Temperature 5°C to 35°C; 10 to 80% R.H. non-condensing
Storage Temperature 5°C to 75°C; 10 to 80% R.H. non-condensing
Dimensions 40cm (D) x 45cm (W) x 13.5cm (H)
Weight 14.15kg
Standard Accessories
Leads Test Leads
Cables Communication cable
Bags Transportation bags
Certificates Calibration certificates
Manual User’s manual
Ordering Information
Model Name Description
EuroSMC ETP-3 Winding Resistance Measurement Unit


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