I. General
DC resistance of transformer is the essential item to be tested in semi-finished product, finished product delivery test, installation, handover test and preventive test by electric power department, and is effective to help find manufacturing defects such as materials selection for transformer coil, welding, looseness on connection, strand breaking, wire breaking and so on, as well as hidden dangers after operation. To satisfy the requirement for quick measurement of DC resistance of transformer, our Company has developed YCR9920T three phase winding resistance tester aiming at YN connection winding. The tester can fulfill functions such as simultaneous energization on three phases, independent current sampling, voltage sampling, as well as simultaneous measurement and display of three-phase resistance value and three-phase unbalance rate, thus can significantly reduce test time for DC resistance of transformer, solve the problem of long test duration for DC resistance of each tapped winding of electric power transformer. It requires only 1/3 of the time required by traditional method.

II. Safety Measures
1. Please be sure to read this manual carefully before use of this instrument.
2. Operator of this instrument shall possess common sense on use of general electric equipment or instrument.
3. This instrument can be used both indoors and outdoors with the requirement of avoiding places with rain, etchant gas, excessive dust, high temperature, direct sunshine and so on.
4. Avoid violent vibration of instrument.
5. Repair, maintenance and adjustment on instrument shall be carried out by professional personnel.
6. After test, be sure to wait until the discharging alarm stops before turning off the power and then dismantle test wire.
7. If no-load regulating transformer is measured, wait until the discharging alarm noise stops and then switch the gear.
8. During the test, it is prohibited to move test clip and power supply line.

III. Performance Features
1. The instrument has big current output and can select current automatically; convenient for operation.
2. Three-channel measurement, real time collection, simultaneous measuring of three resistance values and calculating three-phase resistance unbalance degree.
3. Not only able to measure three phases simultaneously, but also able to measure with single channel as traditional method; possessing temperature conversion function, convenient for use.
4. Possessing perfect protective circuit which is highly reliable.
5. Built-in calendar clock, 500 sets of data storage, retrieval and printing function.
6. Be able to set printing information such as phase sequence and tapping position of resistance.
7. Industrial plastic shell case with light weight; convenient for carrying.
8. Possessing audio discharging alarm with clear discharging indication to reduce misoperation.

IV. Technical Indicators
1. Output current: select current automatically (maximum 20 A)
2. Range ability: 0-100 Ω
3. Accuracy: ±（0.2%+2個字）
4. Minimum resolution: 0.1 μΩ
5. Working temperature: -20-40℃
6. Ambient humidity: ≤80%RH, no condensation
7. Altitude: ≤1000meters
8.Working power supply: AC220 V±10%, 60 Hz±1 Hz
9. Volume: L 400 mm*W 340 mm*H 195 mm
10. Net weight: 8 kg