For measuring winding resistance of highly inductive power transformers consider the Vanguard LTCA-40 Load Tap Changer Analyzer.
Triple resistance-reading channels allow the Vanguard LTCA-40 Load Tap Changer Analyzer to measure three winding resistances simultaneously. Four-wire (Kelvin) connections provide high accuracy and require no lead compensation. A special feature of the Vanguard LTCA-40 is its ability to measure and graph the resistance trace of a transformer LTC during operation. Using a 60Vdc power supply, the Vanguard LTCA-40 is capable of outputting 40 amperes.
Transformer Load Tap Changer Control
Transformer tap positions can be changed re-motely using the unit’s built-in transformer load tap changer. This remote-controlled tap changer feature eliminates the need to manually change a transformer’s step-up and step-down taps.
Resistance Reading Features
Three resistance-reading channels can measure resistance from 1 micro-ohm to 500 ohms, and the test current is programmable (1A, 5A, 10A, 40A). The unit can also be used to measure EHV circuit-breaker contact resistance, motor winding resistance or any low resistance.
Features a back-lit LCD screen (128 x 64 pixels) that is viewable in both bright sunlight and low-light levels. A rugged, alpha-numeric, membrane keypad is used to control the unit.
Built-in Thermal Printer
The built-in 4K” wide thermal printer can print the breaker contact analysis results in both tabular and graphic formats.
AC Motor Current Monitoring
One AC current monitoring channel is dedicated to monitoring the LTC voltage regulator motor current during operation. The motor current is also printed on the resistance graph and can help detect LTC voltage regulator motor problems. An AC clamp-on current sensor is provided.
Built-in Safety Features
At the end of each test, the unit automatically dissipates the stored energy in the transformer. This discharge circuit will continue to work even if the supply voltage is lost.
Dynamic Resistance Testing
One resistance reading channel is dedicated to dynamic resistance testing. This test can monitor the LTC voltage regulator contact resistance during operation. A resistance graph, plotting resistance over time, can be printed on the built-in thermal printer and is very useful for detecting LTC voltage regulator contact problems.
Internal Test Record Storage
Store 128 static test records (48 tests per record) and 11 dynamic resistance test records in Flash EEPROM. Test records can be recalled locally or transferred to a PC via the available interfaces (RS-232C port, USB port, USB Flash drive port).
USB Flash Drive and PC Interface
A built-in USB Flash drive interface provides a convenient method for transferring test records to or from a USB Flash drive. Test records can also be transferred directly to a PC via the RS-232C or USB interface ports. If using a USB Flash drive, test records stored in the unit’s internal memory can be transferred to the drive, and then the supplied PC software can be used to view the test records stored on the drive. Up to 999 test records can be stored on a USB Flash drive.