AC contactor selection method - Solutions - Huaqiang Electronic Network

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin
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1. Series and Parallel Use of Contactors Many consumers use single-phase loads, so multi-pole contactors can be used in parallel to handle such applications. Examples include resistance furnaces and electric welding transformers. When using multiple poles in parallel, a smaller-rated contactor may be sufficient. However, it's important to note that the agreed heating current doesn't scale linearly with the number of poles connected in parallel. This is because the resistance in the active and static contact loops might not be equal, leading to uneven current distribution. As a result, the current capacity after parallel connection is limited—typically up to 1.8 times for two poles and 2 to 2.4 times for three poles. Additionally, since the contacts don't switch simultaneously in a parallel configuration, the switching capability isn’t improved. In some cases, contactors can be used in series. This increases the contact gap, which helps divide the arc into segments, improving arc extinction and speeding up the process. Therefore, the operating voltage can be increased when connected in series, but the rated insulation voltage must not be exceeded. The agreed heating current and rated operating current remain unchanged after series connection. 2. Influence of Power Frequency The frequency of the power supply affects the skin effect in the main circuit. At higher frequencies, the skin effect becomes more pronounced. For most products, the temperature rise in the conductive circuit is relatively low at both 50 Hz and 60 Hz. However, the coil of the contactor should be considered carefully. If a 50 Hz-designed coil is used at 60 Hz, the magnetic flux will decrease, reducing the suction force. It’s crucial to check if the design margin is sufficient. Normally, it's best to use the contactor according to its specified frequency. Always order based on the actual power frequency you’ll be using. 3. Influence of Operating Frequency The number of operations per hour significantly affects contact wear. This factor must be considered when selecting a contactor. The applicable operating frequency is usually listed in the technical specifications. If the actual operating frequency exceeds the recommended value, the contactor must be de-rated to ensure safe and reliable operation.

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Hangzhou Qiantang River Electric Group Co., Ltd.(QRE) , https://www.qretransformer.com