No-load loss: When the secondary winding of the transformer is open and the rated voltage of the sinusoidal waveform of the rated frequency is applied to the primary winding, the active power consumed is called the no-load loss. The algorithm is as follows:
No-load loss = no-load loss process coefficient × unit loss × core weight load loss: When the secondary winding of the transformer is short-circuited (steady state), the active power consumed when the primary winding flows through the rated current is called the load loss. The algorithm is as follows:
Load loss = maximum resistance loss of a pair of windings + additional loss additional loss = winding eddy current loss + loop loss around the wire + stray loss + lead loss impedance voltage: when the transformer secondary winding is shorted (steady state), primary winding The voltage applied by circulating the rated current is called the impedance voltage Uz. Usually Uz is expressed as a percentage of the rated voltage, ie uz=(Uz/U1n)*100%
åŒ Potential:
u=4.44*f*B*At,V
Where: B—magnetic density in the core, T
At-core effective cross-sectional area, square meters can be converted into a commonly used formula for transformer design calculation:
When f=50Hz: u=B*At/450*10^5,V
When f=60Hz: u=B*At/375*10^5,V
If you already know the phase voltage and the number of turns, the zeta potential is equal to the phase voltage divided by the transformer no-load loss calculation - the no-load loss of the transformer.
The no-load loss includes the hysteresis and eddy current loss in the core and the loss of the no-load current on the primary coil resistance. The former is called iron loss and the latter is called copper loss. Since the no-load current is small, the latter can be omitted, so the no-load loss is basically the iron loss.
There are many factors affecting the transformer no-load loss iron loss, which is expressed in mathematical formula. In the formula, Pn and Pw - represent hysteresis loss and eddy current loss kn, kw - constant f - the frequency of the applied voltage of the transformer Maximum flux density in iron core / m 2
n——Shijie Inmez constant, for commonly used silicon steel sheets, when Bm=(1.0~1.6) Wei/m2, n≈2, for the directional silicon steel sheets currently used, take 2. 5 to 3.5.
According to the theoretical analysis of the transformer, assuming that the primary induced potential is E1 (volts), then:
E1=KfBm(2)
K is the proportional constant, which is determined by the number of primary turns and the cross-sectional area of ​​the core. The iron loss is:
Since the primary leakage impedance voltage drop is small, if neglected,
E1=U1(4)
It can be seen that the transformer no-load loss iron loss has a great relationship with the applied voltage. If the voltage V is a certain value, the transformer no-load loss iron loss does not change (because f does not change), and because U1=U1N during normal operation, No-load loss is also called constant loss. If the voltage fluctuates, the no-load loss changes. The iron loss of the transformer is related to the core material and the manufacturing process, and has nothing to do with the load.
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