Dry type transformer can improve work efficiency and promote the continuous development of economy. The economic efficiency of dry-type transformer is the key to enhance the value of dry-type transformer. What is the embodiment of the efficiency of dry-type transformer? Generally speaking, the efficiency of dry-type transformer is reflected in the following points:

1.1 efficiency of dry-type transformer and efficiency of voltage transformer.

Loss = pshcip + P + p2pk, so the efficiency of dry-type transformer is: medium SH is the rated capacity of dry-type transformer (kVA); costis the power factor of load.

Obviously, the efficiency n of dry-type transformer is a function of load rate.

2. For a long time, whether the utilization rate of dry-type transformer capacity is lower than a certain value has been regarded as the standard of dry-type transformer energy saving. In fact, sometimes this standard is not saving electric energy, but wasting electric energy.

The direct reason for this error is that when the dry-type transformer is considered as "big horse pulling small car" according to the capacity utilization ratio, the small capacity dry-type transformer with high utilization ratio must replace the large capacity dry-type transformer, so the iron loss is only considered and the copper loss is ignored. In fact, for a certain load, the active power loss of small capacity is greater than that of large capacity dry-type transformer, so it is a waste of electric energy. The correct power saving calculation should be derived from the following steps: active power loss of large capacity dry-type transformer: load rate of large capacity dry-type transformer; PDK - short circuit loss of large capacity dry-type transformer, kW. Active power loss of small capacity dry-type transformer: when a pump house is in normal operation, there are two pumps running at the same time, and each pump is driven by a 100kW motor, so the constant load is 200kW, CST = 0.9. Originally equipped with a 750kva dry-type transformer, its capacity utilization rate is only about 34%, which is regarded as "big horse pulling car", and then replaced with a 250kVA small dry-type transformer However, the measured parameters of the two dry-type transformers are shown in Table 1. The measured parameters of the dry-type transformers are as follows: capacity (VA), iron loss (W) and copper loss (W). First of all, according to the conventional calculation method (ignoring copper loss), the power saving is obtained: the above results show that the loss of the large capacity dry-type transformer is less than that of the small capacity dry-type transformer, which is a waste of electric energy.

The main reason is that the conventional calculation method ignores the copper loss.

From the above, it can be seen that from the perspective of power saving, in some cases, the dry-type transformer "small horse pull small car" is not as good as "medium horse pull small car", or even not as good as "big horse pull small horse", so the calculation must consider the dry-type transformer no-load and load loss, in order to make a correct conclusion on power saving or power consumption. According to the relationship between the load rate and the capacity of dry-type transformer, it is concluded that: 3. The optimal load rate and power saving of transformer substitute formula (9) into formula (8) to get the load factor of dry-type transformer, i.e. the operating load and rated capacity of dry-type transformer 1. This paper gives an example to illustrate the two side P derivative of acadc Gaal electrnk contact toe ground type, and then subtract the active power loss of small capacity dry-type transformer from the active power loss of large capacity dry-type transformer Power consumption: formula (7) minus formula (10) to obtain the complete formula for calculating the power saving of dry-type transformer: when the dry-type transformer has low operating loss and high efficiency, the load factor is the best, and when the actual copper loss is equal to the iron loss, the dry-type transformer has high efficiency.

The efficiency of dry-type transformer is: n = P2 / p1x10%, that is, when the copper loss of dry-type transformer is equal to the iron loss, the efficiency is high. Therefore, the optimal load rate of dry-type transformer is: 0 = P / PK. Considering the active power loss caused by reactive power transmission in the system during the operation of dry-type transformer, the optimal load rate is modified to: from the formula of optimal load rate, it can be seen that the high efficiency of dry-type transformer does not appear at full load Generally, the capacity of dry-type transformer is about 50%. However, when we choose the capacity of dry-type transformer, we should choose a reasonable dry-type transformer according to the load condition and good load rate, so as to make the dry-type transformer in a good economic state and achieve the purpose of power saving.

3. Selection of dry-type transformer economic capacity 41 selection of dry-type transformer capacity economic operation principle selection of dry-type transformer capacity should start from the purpose of energy saving, first of all, should consider the use of the environment and the selection of low loss dry-type transformer; second, according to the production requirements to calculate the need for large load, and then according to the optimal load rate to select the appropriate dry-type transformer capacity.

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