I.Overview

     The Transformer DC Resistance Tester is a mandatory test item for semi-finished products and finished products factory test, installation and handover test, and preventive test of the power department in the transformer manufacture industry. It can be used to effectively detect the defects in poor material selection, loose welding and connection parts, missing strands and broken wires of the transformer coil, as well as the operation hidden dangers. In order to meet the requirements of rapid measurement of transformer DC resistance, a large-scale power transformer DC resistance rapid tester integrated with Three-Phase simultaneous test function, Magnetic Augment Function, and Degauss Function into one body has been developed in our company. The tester has the functions of three-phase simultaneous power-on, independent current and voltage sampling, simultaneous measurement and display of three-phase resistance and three-phase unbalance rate, so as to greatly shorten the test period of transformer DC resistance and solve the problems about long time consumption for DC resistance measurement of each tap winding in power transformers. 

II. Safety Measures

1) Must read this manual carefully before using the tester;

2) The tester operator should understand the common knowledge on general electrical devices or instruments;

3) The tester can be used indoors and outdoors, but it should be protected from rain, corrosive gas, excessive dust, and high temperature;

4) The tester is a precision instrument and any severe vibration must be avoided;

5) The tester should be maintained, repaired and adjusted by professionals;

6) After the test, be sure to wait for the discharge alarm to stop before turning off the power and removing the test wires;

7) When measuring the no-load voltage-regulating transformer, the tap changer can be switched only after the discharge indication alarm stops.

8) During the test, do not move the test clips and the power lines.

III. Functional Characteristics

1) The tester can select corresponding output current value according to test products, and is mainly suitable for measuring the inductive DC resistance on transformers;

2) On large transformers with a five-leg core and low-voltage windings connected in delta, the tester can be used for the test in HV & LV series excitation mode. The magnetic augment circuit of the windings can be automatically connected in the tester, to quickly and accurately test the DC resistance of the low-voltage windings;

3) The tester has a Three Phases Test function to measure the three-phase DC resistance of the star-connected windings synchronously and calculate the three-phase unbalance rate automatically, so as to greatly reduce the measurement period and improve the test efficiency. Its phase by phase test function can also be used for phase by phase test on transformers with YN and D (Y) connections;

4) The winding material can be set according to the winding material of the transformer, such as copper or aluminum, to distinguish the conversion temperature coefficient of different materials.

5) The tester is equipped with transformer YN winding neutral point lead line resistance detection function, can make three-phase test data closer to the single-phase test value.

6) The tester has a complete protection circuit and sound discharge alarm, to inform the clear discharge indication and reduce the misoperation;

7) The tester is equipped with a 7-inch color touch screen. to display the test data clearly in real-time;

8) The tester has Chinese and English operation interfaces, which can be configured according to the user requirements;

9) The tester is equipped with a RS232 communication port, to transmit the test data to the background, with the control software in the host computer;

10) The tester is equipped with a USB port, to transfer test data into a U disk;

11) The tester has a built-in calendar and clock, as well as saving ( save 100 groups of data), review, and printing functions of test data;

12) The tester has more complete parameter settings, including test windings, Tapping Positions, test phases, Tested Sample Temperature, Conversion Temperature and others of the transformers;

13) The tester is equipped with an industrial plastic case which ensures its good portability and improves its service life.

IV. Technical Indicators

1) Output current:

     Three-phase test: 5A+5A; 1A+1A; 200mA+200mA; 20mA+20mA;

      Single-phase test: 10A; 5A; 1A; 200mA; 20mA;

2) Measurement range:

Three-phase test:  5A+5A: 2mΩ～1.2Ω;

                       1A+1A: 10mΩ～6Ω;

                       200mA+200mA: 100mΩ～30Ω；

                       20mA+20mA: 10Ω～200Ω；

    Single-phase test: 10A: 1mΩ～2Ω;

                       5A: 2mΩ～4Ω;

                       1A: 10mΩ～20Ω;

                       200mA: 100mΩ～100Ω;

                       20mA: 10Ω～20KΩ;

3) Accuracy: ±(0.2%+2 digits);

4) Minimum resolution: 0.1μΩ;

5) Operating temperature: -10～40℃;

6) Ambient humidity: ≤80%RH, no condensation;

7) Power supply: AC220V±10%, 50Hz±1Hz;

8) Tester dimensions: 428mm* 350mm* 230mm (L*W*H);

9) Tester mass: 10.8kg.