R2 : winding resistance at temperature t2, R1 : winding resistance at temperature t1
Because of this, temperatures must be measured when measuring the winding resistances and temperature during measurement should be recorded as well. Winding resistances are measured between all connection terminals of windings and at all tap positions. During this, the winding temperature should also be appropriately measured and recorded. The measuring current can be obtained either from a battery or from a constant(stable) current source. The measuring current value should be high enough to obtain a correct and precise measurement and small enough not to change the winding temperature. In practice, this value should be larger than 1,2xI0 and smaller than 0,1xIN, if possible. A transformer consists of a resistance R and an inductance L connected in serial. If a voltage U is
applied to this circuit;
Here, the time coefficient depends on L/R ratio.
As the measurement current increases, the core will be saturated and inductance will decrease. In this way, the current will reach the saturation value in a shorter time. After the current is applied to the circuit, it should wait until the current becomes stationary (complete saturation) before taking measurements, otherwise, there will be measurement errors.
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