How to choose a single-phase electric meter?
How to choose a single-phase watt-hour meter is more or less in contact with the present family. The use of single-phase watt-hour meter is mainly applied to household watt-hour meters. General household watt-hour meters are initially installed by the electric power department or developers, but some places need to install a single-phase watt-hour meter to measure the use of electricity. Here we introduce how to choose single-phase watt-hour meter for later use.
How to choose a single-phase watt-hour meter?
1. Determining the Range
Why do we first determine the measurement range of single-phase watt-hour meter? In order to use safely in the later period, it is necessary to ensure that the current of the meter under test does not exceed the maximum measured value. The configuration of single-phase watt-hour meter depends on the debt power. The current of single-phase electrical apparatus is 4.5A per kilowatt, so the range of the meter should be 1.2-1.5 times of the current. If the total power of a household appliance is 4KW and the current is 18A, a 5 (20) A single-phase watt-hour meter can be selected.
2. Capacity determination
The general voltage specification of single-phase watt-hour meter is 220V, and the current specification is 1.5 (6) A, 5 (20) A, 5 (60) A, 15 (60) A, 20 (80) A, etc. The selection of current specifications mainly depends on the user's load. The upper limit of general load current should not exceed the rated current of the watt-hour meter, and the lower limit should not be lower than the specified load current within the allowable error range of the watt-hour meter. For example, the total power of the user is about 10 KW, the voltage is 220 V, and the current is 10 000 220_46A. That is to say, the current value is about 46 A when the power is divided by 220. Considering the reserved margin, the current specifications of 5 (60) and 15 (60) A can be selected. You can also choose a smaller current specification and connect it to the current transformer.
3. Selection of Current Transformer
Current transformer is selected for users who have large current. It can convert the primary current with larger value to the secondary current with smaller value through a certain way, which can be used for protection and measurement purposes. For example, 100/5 current transformer can convert 100A current into 5A current. The selection of current transformer specification is mainly for low-voltage users. Because the power consumption of low-voltage users may change at will, the power consumption estimation is not accurate, so the transformer specification is not good for fixed selection, usually calculated according to the known power consumption. For example, the power consumption is 100 KW users, the voltage is 220 V, the current is about 100 000_220_455A, and the reserved margin needs to be taken into account. The current transformer of 500A needs to be selected. The secondary output current of the transformer is usually 5A. Therefore, the transformer of 500 to 5 should be selected. As for the accuracy of the current transformer, it needs to be at least in the same level as the meter.
Matters needing attention in selecting single-phase watt-hour meter
1. Brand Selection Guarantees Quality
The watt-hour meter belongs to the compulsory measurement instrument of the state. According to the provisions of the metrology law, the selected watt-hour meter must have a CMC certificate issued by the Technical Supervision Bureau at or above the provincial level. This is the basic condition and legal procedure for watt-hour meter manufacturers to be recognized by power companies. Generally, the existing enterprises are mainly regular brand enterprises, such as Changsha Weisheng, Shenzhen Kelu, Ningbo Samsung, Hangzhou Huali and so on. In addition to having the basic necessary conditions, these brand enterprises are basically large enterprises for more than 10 years. They are closely linked from R&D, technological innovation, production process, product sales and after-sales service. They must strictly check and strive for excellence and service guarantee at every step. Everyone knows that watt-hour meter is a long-term energy measurement tool. Instead of checking the accuracy of measurement, it will be more likely to lose because of small losses. Moreover, after-sales service is not in place. Later replacement will be more troublesome. Therefore, we suggest that you carefully consider the choice of brand.
2. Choosing a Regular Watt-hour Meter without Seeking to Be Cheap
Nowadays, many low-cost watt-hour meters are mostly manufactured by workshop. Although they are not recognized by the electric power department, they are still sold in the market because of their low price, not to mention that they can not be used. However, the price of single-phase watt-hour meters with tens of yuan is almost so much from raw materials and components. Then other production costs, such as manpower and material resources, are acceptable to everyone. Imagine the quality of low-cost watt-hour meters? Therefore, in order to avoid people buying and replacing, there are dangerous hidden dangers in the use of replacement, we suggest that we carefully consider the choice, not cheap choice of formal single-phase watt-hour meters produced by regular manufacturers.
