DC contactors knowledge Daquan

DC contactors knowledge Daquan

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DC contactors * Overview
DC contactor is a frequently used long-distance making and breaking DC main circuit and high-capacity electrical control circuit for the vacuum interrupter medium, small size, high pressure, breaking ability, long life, contact maintenance-free, especially because the arc is not exposed, safe and reliable, widely used in DC circuits in mining, metallurgy, shipbuilding, subway, chemical, electric power and other sectors of traction. Its main target is to control the electric motor can also be used to control other electrical loads such as electric heaters, lighting, welding machine, such as a capacitor. The product is supported by a suitable operating mechanism can be installed into the high and low voltage AC vacuum contactor and high and low voltage AC vacuum circuit breaker interrupter accessories for power distribution control, special suitable composition flameproof vacuum switch.
DC contactor selection, first look at the application control circuit, the contact function in the line, because the DC contactor main contacts have single and double points, a single contact contacts mainly for power generation – electric system, or other independent variable flow system, features are: 1 ready, allowed to run. 2 accident conditions quickly cut off the main circuit. Therefore contactor rated current, rated voltage, arc-breaking ability, must meet the system requirements. Double contact contactor is used: non-independent power supply system; reversible system, etc. Also note that the rated current, rated voltage, arc breaking capability. Finally, pull coil voltage, to go along with the operating system requirements. Furthermore pull coil is large, we want to add RC absorb loop inductance to prevent potential breakdown itself, or related equipment.

      DC contactors * Composition and Structure

 

    DC contactor is mainly used for long-distance making and breaking DC circuit and frequent start, stop, reverse and reverse brake DC motors, it is also used frequently turned on and off lifting magnet, solenoid valves, clutch an electromagnetic coil. DC contactors, three-dimensional arrangement and layout of the two structures, some of the product is based on the AC contactor derived. Thus, the same basic structure and principles of work with AC contactor DC contactor is mainly composed of three parts electromagnetic mechanism, contact system and extinguishing device components.

(1) Electromagnet DC contactor solenoid mechanism by the core, and the armature coil, etc., around the edges and corners of rotating multi-use structure Clapper. There are forms of exercise armature pivoting of Clapper and linear motion of the linear motion, linear motion-type armature can be divided into suits and flip direct-acting direct-acting (ie contacts below the electromagnetic means). Since the coil through the direct current, during normal operation, it does not produce a vortex core, the core does not heat, no iron loss, so the core is made available piece of cast iron or steel. DC contactor coil more turns, in order to make good heat dissipation coil, coil winding typically grow thin cylindrical shape. Due to the constant flux in the core, the core pole face and therefore we do not need to short-circuit loop. In order to ensure reliable release of the armature, which require the armature core and between the non-magnetic spacer pad, to reduce the effect of residual magnetism. 250A above DC contactors are often used in series two-wound coil l to start the coil, the coil 2 in order to maintain coil contactor a normally closed contact with the holding coil in parallel. In the circuit just turned moment, the coil 2 is normally closed contacts shorted, can l get a larger coil current and suction. When the contactor operation, normally closed contacts disconnect the coil 1 and the coil 2 is energized in series, since the voltage constant, so the current is small, but still maintain the armature is attracted, to save power and prolong the life of the electromagnetic coil the goal of.

    (2) contact system has a DC contactor main contacts and auxiliary contacts. The main contacts for switching on, off large current load circuit that is the main circuit. Therefore, the main contact cross-sectional area is larger, generally planar. Smaller cross-sectional area of the auxiliary contacts, generally spherical shape, and for turning on, off control circuit, a signal circuit. AC contactor main contacts are mostly normally open contact, auxiliary contact, there are two kinds of normally open contacts and normally closed contacts. AC contactor contact has a double break bridge and finger-type single break and other types. Main contacts are typically made unipolar or bipolar, because the contacts on or off current is large, so the use of rolling contact finger contact. Auxiliary contacts off current is small, often with double break point contact bridge contact.

(3) Since the DC arc interrupter device, unlike AC arc natural zero crossing, DC contactor main contacts in breaking a large current (DC circuit), the more difficult interrupter, often have a strong arc, easy to burn contact and delay off. In order to rapidly arcing, DC contactors generally use magnetic blow interrupter device, and equipped with a separator and clay interrupter cover. Small-capacity DC contactors there is also a permanent magnet generating a magnetic force of the blow of large-capacity contactors are common longitudinal seam plus magnetic blow interrupter interrupter method. AC contactor interrupter device has gate films interrupter, electric power interrupter, longitudinal seam interrupter, magnetic blow interrupter several. unipolar or bipolar, because the contacts on or off current is large, so the use of rolling contact finger contact. Auxiliary contacts off current is small, often with double break point contact bridge contact. That is the main circuit circuit. Therefore, the main contact cross-sectional area is larger, generally planar. Smaller cross-sectional area of the auxiliary contacts, generally spherical shape, and for turning on, off control circuit, a signal circuit. AC contactor main contacts are mostly normally open contact, auxiliary contact, there are two kinds of normally open contacts and normally closed contacts. AC contactor contact has a double break bridge and finger-type single break and other types. Main contacts are typically made unipolar or bipolar, because the contacts on or off current is large, so the use of rolling contact finger contact. Auxiliary contacts off current is small, often with double break point contact bridge contact.

      DC contactor works *

 

    When the contactor coil is energized, the coil current produces a magnetic field that generates electromagnetic static core suction to attract the moving core, and promote contacts Action: normally closed contacts disconnect, normally open contact closure, the two are linked. When the coil power, the electromagnetic suction disappeared, the armature is released under the action of the spring is released, the contacts recovery: normally open contact open, normally closed contact is closed.

In addition, the DC contactor use in DC-powered circuit which more than made DC pump, which is a power outage at the plant when the security system of the turbine motor oil, which is controlled by DC, its main circuit DC, auxiliary circuit DC also, of course, also be a contactor DC.

    AC for power equipment, motor control and power protection equipment, as well as emergency lighting. Parameters like noise, I’ve seen AC and DC contactors, poor quality and noise are big. The internal resistance, because different voltage levels, it is different.

* Selection of DC contactor mode

1. Select the type of DC contactor DC contactor type should be based on the severity of the load current and load type to choose, that is, AC load and DC load is a light load, the general load or a heavy load.

    2. DC contactor main contacts rated current of the DC contactor main contacts rated current of main contacts can be calculated IN ≥PN /(1~1.4)UN motor contactor control DC motor if the motor starts, the system according to the empirical formula Fixed or reverse frequently, usually the contactor main contacts rated current drop one to use.

3. main contact contactor nameplate rated voltage if the voltage means the main contacts can withstand the rated voltage, the voltage is not attracting the coil, when using the contactor main contacts rated voltage should be not less than the rated voltage of the load.

    4. Select the operating frequency of operating frequency refers to the contact number of times per hour off. When a large current and off-off frequency is too high, it will cause serious overheating of the contacts, even welding operating frequency if it exceeds a predetermined value , should be used DC contactor rated current large level.

5. Select the rated coil voltage Coil rated voltage is not necessarily equal to the rated voltage of the main contact, when the line is simple, use of electrical appliances is low, it can be directly used voltage 380V or 220V, such as circuit complexity, use of electrical appliances more than 5h, available 24V, 48V or 110V voltage (1964 and international regulations for the 36V, 110V, or 127V) coils.

      DC contactors * Role

 

    DC contactor is mainly used for long-distance making and breaking DC circuit and frequent start, stop, reverse and reverse brake DC motors, it is also used frequently turned on and off lifting magnet, solenoid valves, clutch an electromagnetic coil. DC contactors, three-dimensional arrangement and layout of the two structures, some of the product is based on the AC contactor derived. Thus, the same basic structure and principles of work with AC contactor DC contactor is mainly composed of three parts electromagnetic mechanism, contact system and extinguishing device components.
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