(1) Select the type of contactor. AC contactors should be used for AC loads, and DC contactors should be used for DC loads. If the control system is mainly an AC motor, and the capacity of the DC motor or DC load is relatively small, it can be controlled by the AC contactor, but the rated current of the contact should be selected appropriately.
In three-phase AC circuits, three-pole contactors are generally selected; in single-phase and DC systems, two-pole or three-pole parallel connections are commonly used. When the AC contactor is used in a direct current system, it can also be used in various stages in order to improve the breaking capacity.
(2) Selecting the rated voltage and rated current of the contactor main contact Normally, the rated voltage of the contactor contact is not lower than the rated voltage of the load circuit. The rated current of the main contact is not lower than the rated current of the load circuit.
(3) Determination of control circuit and auxiliary circuit parameters The contactor coil voltage should be determined according to the selected control circuit voltage. Under normal circumstances, more use of AC control, when the operation is frequent when the use of direct current (220V, l10V two) control.
The type and number of contactor auxiliary contacts can generally be determined within a certain range according to the system control requirements of its normally open, normally closed number and combination of forms, and should pay attention to the auxiliary contacts of the ability to switch off. When the number of contacts and other rated parameters do not meet the system requirements, a contactor or relay can be added to expand the function.
Under normal circumstances, when the circuit has 1~5 contactors, the control voltage can be 380V. When the circuit exceeds 5 contactors, the control voltage is 220V or 110V. At this time, control transformers for isolation are required.
(4) Verification of dynamic and thermal stability When a three-phase short-circuit occurs on the line, the short-circuit current should not exceed the dynamic and thermal stability values ​​of the contactor. When the contactor is used to cut off the short-circuit current, the breaking capacity should also be verified.
(5) Permissible operating frequency verification The operating frequency allowed by the contactor is checked according to the number of operations. When the contactor operates frequently in the following cases, the actual operating frequency exceeds the allowable value, close-contact start-up, reverse brake and frequent positive and negative reversals, etc. In order to prevent ablation and premature damage of the main contact, the rated current of the contact should be Reduce use, or switch to heavy duty contactors. This contactor, due to the use of silver-iron powder metallurgy contacts, improves the arc extinguishing measures and therefore can accommodate more arduous work at the same rated current.
HCH Hardware is a bolt manufacturer and provides all kindsof fasteners since 2008. Our main products includestandard bolts, nuts, Screws, washers, Pins and OEM parts. We have integrated resources from more than 50 top level fastener factories in Jiaxing, Haiyan, Ningbo,Dainan, Qintongareas, and have established long term relationships with them.We arenow serving for over 60 customers in South and North America.We can provide you with one stop services to meet you different needs, which can save your purchasing cost and optimize your efficiency. HCH Hardware was certified by ISO9001-2015 on 02/25/2021.We especially emphasize on products quality,HCH Hardware have necessary conditions for quality control with applicable processes and experienced experts. Appropriate production processes and quality control
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