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Single-phase transformers are more energy efficient
Is the single-phase transformer low loss? In the previous papers on the introduction of single-phase transformer and single-phase power supply technology, it is believed that the single-phase transformer has less no-load loss, energy saving and low change loss than the three-phase transformer of the same capacity. Some papers list the application examples. When referring to the economic benefits of transformation, use D10, D11 or even D12 series transformers to compare with S9 series transformers of the same capacity. Phase transformers have much lower no-load losses, so it is a misconception that single-phase transformers are more economical to operate than three-phase transformers. In the example, the difference in technical level between the two is ignored. According to JB/T3837-1996 'Methods for the Modeling of Transformer Products', the performance level of the serialization of the transformer model is stipulated. The performance parameters of the first size To raise to a new level. For example, D10 series transformers are designed according to the parameters of S10 transformers. When demonstrating the effect of reducing loss of D10 or D11 series transformers, S10 or S11 transformers of the same type should be selected for comparison. It is actually unfair to select S9 series transformers as reference objects. .
In addition, ordinary S9 series transformers adopt a stacked core structure, while D10, D11, etc. mostly adopt a coiled core structure: there are differences in technology between stacked cores and coiled cores, and the coiled core structure overcomes the The shortcomings that cannot be overcome in the traditional stacked iron core structure, for example, in a core lamination, the length of the magnetic circuit along the outside and along the inside is quite different, so that the magnetic flux is not evenly distributed in the iron sheet, and high-order harmonics are generated. waves, resulting in increased losses. In the three-phase iron core, in the intersection area of the iron yoke and the core column of the B phase, the rotating magnetic field is generated due to the three-phase magnetomotive force, which increases the loss, and there is a seam at the butt joint between the iron core laminations. In the region of the seam, there is flux transversely across the lamination which increases losses. Therefore, the no-load loss and no-load current of the wound core transformer are smaller than that of the stacked iron core transformer. The three-phase coiled iron core sealed transformer with a capacity of 100 kVA of the same type 11 and the single phase coiled iron core transformer have obvious difference in weight, but the difference in technical indicators is not obvious. Therefore, the conclusion that the single-phase transformer has smaller loss and energy saving than the three-phase transformer has no basis.
Low folding line loss
Does the single-phase power supply mode have low line loss? According to the circuit principle, the same power P is transmitted at the same distance, and the power factor is 1. The line losses of the three-phase power supply mode and the single-phase power supply mode are as follows. Assume that wires with the same cross section are used, and the resistance of the wire is R. A single-phase transformer supplies power in two-wire mode. When transmitting power P, the current in the phase line and the neutral line is I, and the resulting line loss is P Single loss = 2I^2R. The three-phase transformer supplies power in three-phase four-wire mode. When transmitting power P, the phase current in the line is I /3. Under ideal conditions, there is no current in the neutral line, and the phase loss of the phase line P = (I/3)R = IR/9.
In this mode, the line loss is P3 loss = 3×(I /3)R = IR/3. It can be seen from the calculation that the line loss of the three-phase power supply mode is the lowest, and the loss of the single-phase power supply mode is 6 times higher than that of the three-wire system. It can be seen that the single-phase power supply method has no advantage in reducing line loss compared with the three-phase power supply method.