How to choose the meter transformer?

The selection of the transformer and the electric energy meter should be considered comprehensively according to the accuracy requirements of the measured unit, the load size of the measured unit, and the use environment. How to choose electric meters and transformers is a big problem for many people who need to buy electric meters. In fact, in many cases, electric meters and transformers cooperate with each other to meet the needs of users, so the choice of meters and transformers can be listed as follows To proceed. For example, the load of the production workshop in an industrial park is calculated based on the current of 2 amperes per kilowatt, and the transformer and electric energy meter are selected as follows:

1. 75kW:

1. Transformer: Low-voltage cast-type current transformer with a transformation ratio of 150/5, an accuracy of not less than 0.5S, and a capacitance of not less than 20VA;

2. Electric energy meter: 3×220/380V 3×1.5(6)A, an electronic three-phase four-wire electric energy meter with an accuracy of not less than 1.0;

2. 140kW:

1. Transformer: A low-voltage cast-type current transformer with a transformation ratio of 250/5, an accuracy of not less than 0.5S, and a capacity of not less than 20VA should be selected;

2. Electric energy meter: 3×220/380V 3×1.5(6)A, an electronic three-phase four-wire electric energy meter with an accuracy of not less than 1.0;

0.5S class current transformer can choose 1.0 class electronic energy meter; 0.2S class current transformer can choose 0.5/0.2 class electronic energy meter. According to the regulations: the rated current of the meter connected through the current transformer should be controlled within 30% of the rated secondary current of the current transformer, and the maximum rated current should be about 120% of the rated secondary current of the current transformer.

Third, the accuracy of the meter and the transformer

The meter's measurement accuracy is divided into 0.1S, 0.2S, and 0.5S levels. The smaller the accuracy, the more accurate and the higher the price. A current transformer changes a large current into a small current according to the transformation ratio of the transformer. For example, 150/5 means that a large current is reduced by a ratio of 1/30. The purpose is first to reduce the cost of metering equipment, and secondly to standardize the meter. The current of the meter is 1A or 5A. The specific choice depends on the transformation ratio of the current transformer. For example, 150/5 choose 5A meter, 150/1 Choose 1A meter.

When the meter reads, it needs to be multiplied by the transformation ratio just now to get the final power consumption. The current transformer ratios of current main specifications are 50/5, 75/5, 100/5, 150/5, 200/5, 250/5, 300/5, 400/5, 600/5, 800/5 , 1000/5, 1200/5.

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