电气设备433
3功率因数校正
3.2功率因数连接方法
表4显示了电容器组的无功功率Qc
[kvar]连接到ABB变压器的二次侧，根据不同的
小估计负荷水平。
表4:ABB变压器的PFC无功功率一台三相异步电动机，110 kW（400 V-50 Hz-4极）
表中建议的PFC功率为30 kvar。
三相变压器的单独功率因数校正
变压器是重要的电气设备，由于
系统需求，通常是不断在服务。
特别是，在由多个变电站组成的装置中
建议直接在变压器上进行功率因数校正。
通常，PFC功率（Qc
)对于额定功率Sr的变压器
[kVA]
不应超过小参考负载下所需的无功功率
条件
从变压器铭牌上读取数据时
空载电流i0
%，短路电压uk的百分比值
%,
铁损耗Pfe和铜损耗Pcu[kW]，所需PFC功率为
大约：
其中KL
是负载系数，定义为小值之间的关系
变压器的参考负载和额定功率。
实例
假设630 kVA配电变压器需要PFC
提供低于其额定功率60%的负载。
根据变压器铭牌上的数据：
一、
0
% = 1.8%
英国
% = 4%
Pcu=8.9 kW
Pfe=1.2 kW
连接到变压器的电容器组的功率因数校正功率为：
而当使用简化公式时，结果是：

质量控制[kvar]
Sr英国%i
o%Pfe Pcu负载系数KL
[kVA][%][%][kW][kW]0.25 0.5 0.75 1
中压-低压配电变压器
50 4 2.9 0.25 1.35 1.4 1.5 1.8 2.3 2.9
100 4 2.5 0.35 2.30 2.5 2.7 3.3 4.3 5.7
160 4 2.3 0.48 3.20 3.6 4 5 6.8 9.2
200 4 2.2 0.55 3.80 4.4 4.8 6.1 8.3 11
250 4 2.1 0.61 4.50 5.2 5.8 7.4 10 14

a three-phase asynchronous motor, 110 kW (400 V - 50 Hz - 4 poles), the PFC power suggested in the table is 30 kvar. Individual power factor correction of three-phase transformers A transformer is an electrical device of primary importance which, due to the system requirements, is often constantly in service. In particular, in installations constituted by several transformer substations, it is advisable to carry out power factor correction directly at the transformer. In general, the PFC power (Qc ) for a transformer with rated power Sr [kVA] should not exceed the reactive power required under minimum reference load conditions. Reading the data from the transformer nameplate, the percentage value of the no-load current i0 %, the percentage value of the short-circuit voltage uk %, the iron losses Pfe and the copper losses Pcu [kW], the PFC power required is approximately: where KL is the load factor, defined as the relationship between the minimum reference load and the rated power of the transformer. Example Supposing the need for PFC of a 630 kVA oil-distribution transformer which supplies a load which is less than 60% of its rated power. From the data on the transformer nameplate: i 0 % = 1.8% uk % = 4% Pcu = 8.9 kW Pfe = 1.2 kW The PFC power of the capacitor bank connected to the transformer is: while, when using the simplified formula, the result is: ABB | Electrical devices 433 3 Power factor correction 3.2 Power factor connection method Table 4 shows the reactive power of the capacitor bank Qc [kvar] to be connected on the secondary side of an ABB transformer, according to the different minimum estimated load levels. Table 4: PFC reactive power for ABB transformers Qc [kvar] Sr uk% i o% Pfe Pcu load factor KL [kVA] [%] [%] [kW] [kW] 0 0.25 0.5 0.75 1 Oil Distribution Transformer MV-LV 50 4 2.9 0.25 1.35 1.4 1.5 1.8 2.3 2.9 100 4 2.5 0.35 2.30 2.5 2.7 3.3 4.3 5.7 160 4 2.3 0.48 3.20 3.6 4 5 6.8 9.2 200 4 2.2 0.55 3.80 4.4 4.8 6.1 8.3 11 250 4 2.1 0.61 4.50 5.2 5.8 7.4 10 14