Transformator Coefficient
The transformation coefficient (C) is the ratio of the HH wetness to the HH wetting voltage during the idling of the transformer:
For three-way transformers, the conversion rate is the ratio of the voltages of the HH/CN, HH/H and SN/H.
The value of the transformation coefficient allows the correct number of turns of the transformer ' s flow, so it is determined in all the rim responses and for all phases. These measurements, in addition to checking the transformation coefficient itself, provide an opportunity to check the correctness of the voltage switch on the respective steps and the whole of the flow.
If the transformer is mounted without autopsy and a number of replies are not available for measurement, the transformation factor shall be determined only for accessible responses.
Tribute test Transformation factor It shall be sufficient to check for two pairs of movables, the measurements recommended to be carried out on those boilers for which the short circuit voltage is the lowest.
The passports of each transformer give the nominal voltages of both idling modes. Therefore, the nominal transformation factor can be easily determined in relation to them.
The measured transformation factor at all the steps of the respondent switch shall not differ by more than 2 per cent from the transformation factor in the same response in other phases or from the passport data or from previous measurements. In the case of a larger deviation, its cause must be clarified. In the absence of a turn-off, the transformer may be introduced.
The transformation coefficient shall be determined by the following methods:
(a) Two voltmeters;
(b) AC bridge;
(c) Permanent current;
(g) Model (standard) transformer, etc.
The transformation coefficient is recommended to be determined by two voltmeters (Figure 1).
A basic scheme for determining the transformation coefficient by two voltmeters for single-phase transformers is given in rice. One, a. The voltage to be applied to two transformator straps is simultaneously measured by two different voltmeters.
When testing three-phase transformers, linear voltages corresponding to the same pressures of both validated movables shall be measured simultaneously. The voltage to be applied shall not exceed the nominal voltage of the transformer and shall be excessively small so that the measurement results cannot be affected by errors due to the loss of the voltage in the idling current and the current resulting from the addition of the measuring instrument to the secondary pit.
