1. Purpose
Measure the winding with one-way current to consider whether the splits are right or wrong, the coil is seamless or broken, the quality starts to connect and the welding.
- Before measuring one-way renubbiation, the hiccup switch should operate 3 times.
- Use a specialized bridge to measure the one-way voltage of the coils. If one-way Infinity and Amp are used to measure, these meters must have a minimum accuracy level of 0.5.
- Measure all the high, middle and lower coils at all stages of division, if the Y-fighting coil has a neutral head outwards, measure at A0, B0, C0.
- When measuring the star coil, without the neutral ends taken out, we must measure the one-way voltage of the pairs of coils and the attribution to one phase is as follows:
RAB = RA + RB = aRBC = RB + RC = bRCA = RC + RA = cIn which: a, b, c are the voltage values measured by bridge (or V-A), when attached to the poles AB, BC, CA.
Solving the equation system above we have the following phase-by-phase recoding:
- How to calculate errors:
In it:
Rmax – The largest one-way voltage at the same rung between phases.
Rmin– The smallest one-way voltage at the same rung between phasesLaboratory equipment: Model One-Way Counterometer: VANGUARD/USA's WRM-10P.
2. Measurement method Based on IEC 60076-1:2011 (section 11.2) or QCVN QTD 5:2009/BCT (article 27) and based on the contract of use of WRM-10P/VANGUARD/USA variable ratio measuring device(WRM-10P S2 user's manual)Measurement diagram: 
Figure 8: 1 phase transformer coil voltage measurement test diagramFigure 
9: Experimental diagram measuring 3 phase 3 transformer coils.
Assess the results of one-way voltage value measured when compared with the factory document and compare betweenphases with each other if the deviation is not more than 2% is satisfactory.
