Table of Contents

Product Introduction

Residual magnetism left after transformer DC resistance measurement causes core saturation, inrush current, protection misoperation and equipment vibration. HF-TC-646 integrates DC resistance measurement and intelligent demagnetization in one unit. It adopts hysteresis loop tracking demagnetization technology, quantifies residual magnetism rate, and completes testing and demagnetization with single wiring for three-phase transformers. Widely used for handover and preventive tests of power transformers.

Main Features

DC resistance supports auto/manual adjustable output current, three-phase simultaneous measurement and unbalance rate calculation.
Built-in copper/aluminum temperature conversion, historical data comparison and discharge alarm.
Intelligent hysteresis loop tracking demagnetization, drawing real-time hysteresis curves and monitoring residual magnetism rate.
±90V demagnetization output voltage with fast demagnetization; supports AC220V no-load current comparison test.
7-inch touch screen, Bluetooth & RS485 communication, built-in printer and 380V mis-wiring protection.

Technical Parameters

Module	Item	Specification
DC Resistance Test	Output Current	Auto, 40A, 20A, 10A, 5A, 2A, 1A, 200mA, 100mA, 20mA
	Measurement Range	0Ω ~ 20kΩ (Three-phase simultaneous: 0~120Ω)
	Accuracy	0.2% ±0.1μΩ
	Minimum Resolution	0.01μΩ
Demagnetization Test	Output Voltage	±90V / ±45V
	Max Output Current	≤5A
	Demagnetization Effect	Residual magnetism rate ≤5%
	Minimum Resolution	0.1%
	No-load Output	AC220V±10%, 50Hz
	Voltage Accuracy	0.5% ±1V
	No-load Current Measurement	0~500mA, Accuracy 1.0% ±0.2mA
Overall Specifications	Working Temperature	-20℃ ~ 40℃
	Ambient Humidity	≤80% RH, non-condensing
	Power Supply	AC220V±10%, 50Hz±1Hz
	Dimensions	412mm × 290mm × 330mm
	Net Weight	22.5Kg

Packing List

No.	Description	Qty	Unit	Remarks
1	Main Tester Unit	1	Set	HF-TC-646 DC resistance & demagnetization integrated instrument
2	High-current Test Cable Set	1	Set	Three-phase measuring wires with alligator clamps
3	Power Supply Cable	1	Pcs	AC220V mains cord
4	USB Communication Cable	1	Pcs	For PC connection
5	Bluetooth Communication Module	1	Pcs	Built-in optional, as configured
6	Thermal Printing Paper	2	Rolls	Spare paper for built-in printer
7	Operation Manual (English & Chinese)	1	Copy
8	Factory Calibration Certificate	1	Copy
9	Quality Warranty Card	1	Copy
10	Hard Transport Case	1	Pcs	Shockproof carrying case
11	Spare Fuse	2	Pcs	For maintenance

FAQ

Q1: What problems will residual magnetism bring to transformers?

A1: Residual magnetism leads to core saturation when energized, generating large inrush current, causing relay protection misoperation, transformer vibration and abnormal test data. This instrument eliminates residual magnetism after DC resistance measurement.

Q2: What measuring functions does this tester integrate?

A2: It combines DC resistance testing and intelligent demagnetization. It supports three-phase simultaneous DC resistance test, automatically calculates unbalance rate, and implements hysteresis loop tracking demagnetization with residual magnetism rate quantification.

Q3: Is one-time wiring available for three-phase transformers?

A3: Yes. After wiring, both DC resistance measurement and demagnetization test can be completed without repeatedly changing cables, greatly improving field testing efficiency.

Q4: What is the standard for demagnetization effect?

A4: The demagnetization target is residual magnetism rate ≤5%. The instrument can draw hysteresis curves and display residual magnetism rate before and after demagnetization intuitively.

Q5: What output current options are provided for DC resistance test?

A5: Output currents include Auto, 40A, 20A, 10A, 5A, 2A, 1A, 200mA, 100mA, 20mA, covering various resistance ranges of transformers and current transformers.

Q6: Does the instrument support temperature conversion function?

A6: Yes. It supports copper and aluminum conductor temperature conversion, convenient for comparing measured data with historical records under standard temperature.

Q7: How to export test data?

A7: Equipped with built-in thermal printer for on-site reports. It also supports Bluetooth and RS485 communication to upload data to a computer.

Q8: What safety protection functions are available?

A8: It has 380V misconnection protection, discharge acoustic alarm, to avoid safety risks caused by residual inductive voltage after testing.

Q9: Can I test the no-load current before and after demagnetization?

A9: Yes. It provides AC220V output, supporting comparative test of transformer no-load current before and after demagnetization to verify demagnetization performance.

Q10: What are the working environment requirements?

A10: Operating temperature: -20℃ ~ 40℃; humidity ≤80%RH without condensation. Suitable for substation on-site and factory workshop use, avoid heavy vibration, rain and corrosive gas.

Q11: What is the demagnetization output voltage?

A11: Optional ±90V or ±45V output voltage, maximum demagnetization current ≤5A, featuring fast demagnetization speed.

Q12: Is it necessary to wait for the discharge alarm to finish before switching tap positions?

A12: Definitely. After DC resistance measurement, inductive voltage remains inside the winding. Please wait until the discharge alarm stops before adjusting tap-changer or disconnecting test wires.

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HF-TC-646 Transformer Demagnetization Tester