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DC contactor knowledge
PUBLISHER:Shanghai Moye Electric Co.,Ltd RELEASE TIME:2017/7/13
Introduction to DC contactors
DC contactor is a long-distance frequent and connected to the DC main circuit and large-capacity control circuit of the electrical appliances to vacuum for the arc medium, with a small size, high pressure, breaking capacity, long service life, Contact protection, especially because of its arc is not exposed, safe and reliable, etc., are widely used in mining, metallurgy, ship, subway, chemical, electric traction and other sectors of the DC circuit. The main control object is the motor, can also be used to control other power loads such as electric heaters, lighting, welding machines, capacitors and so on. The product is equipped with suitable operating mechanism, can be installed into high and low voltage AC vacuum contactor and high and low voltage AC vacuum circuit breaker arc extinguishing accessories for power distribution control, especially suitable for the composition of vacuum explosion-proof switch.
The choice of DC contactor, first of all depends on the application of the line control mode, the contactor in the line function, because the DC contactor main contact with a single point, single contactor is mainly used for power generation - electric system, or Other independent variable flow system, the function is: 1 ready, allowed to run. 2 accident state quickly cut off the main circuit. So the contactor rated current, rated voltage, arc breaking capability, must be satisfied with the system requirements. Double contact contactor is used: non-independent power supply system; reversible system, the same attention to the rated current, rated voltage, arc breaking capacity. Finally, the clutch coil voltage, to be attached to the operating system requirements, and then pull the coil is larger, to add RC absorption circuit, to prevent self-inductance potential breakdown itself, or related equipment.
DC contactor composition and structure
DC contactors are mainly used for remote connection and breaking of DC circuits and frequent start, stop, reverse and reverse brake DC motors, also used to frequently turn on and off the lifting solenoid, solenoid valve, clutch Of the electromagnetic coil and so on. DC contactor with three-dimensional arrangement and flat layout of the two structures, and some products are based on the AC contactor derived. Therefore, the DC contactor structure and working principle and AC contactor is basically the same, mainly by the electromagnetic mechanism, contact system and arc extinguishing device composed of three parts.
(1) Electromagnetic mechanism DC contactor Electromagnetic mechanism consists of iron core, coil and armature, etc., and more use around the angular rotation of the clutch structure. The shape of the armature movement of the rotation of the shaft and the linear motion of the straight-line, linear movement of the armature can be divided into straight-mounted direct and flip-type direct drive (that is, the contact in the electromagnetic mechanism below). As the coil is through the direct current, the normal work, the core will not produce eddy current, the core does not heat, no iron loss, so the core can be made of whole cast iron or cast steel. DC contactor coil turns more, in order to make the coil heat is good, usually the coil wound into a long and thin cylindrical. As the magnetic flux in the core is constant, there is no need for a short circuit ring on the pole surface. In order to ensure reliable release of the armature, often between the core and the armature pad with non-magnetic gasket to reduce the impact of remanence. 250A above the DC contactor is often used in series double winding coil, coil l for the start coil, coil 2 to maintain the coil, contactor of a normally closed contact with the holding coil in parallel. In the circuit just after the moment, the coil 2 is normally closed contact short circuit, the coil l can get a larger current and suction. When the contactor moves, the normally closed contact is disconnected, the coil 1 and the coil 2 are connected in series. Since the voltage is constant, the current is small, but the armature can be kept to be lifted to save power and extend the life of the solenoid the goal of.
(2) contact system DC contactor with main contacts and auxiliary contacts. The main contact is used to turn on and off the current circuit, which is the main load circuit. Therefore, the main contact cross-sectional area is large, generally flat type. Auxiliary contact cross-sectional area is small, generally spherical type, for turning on, disconnect the control circuit, signal circuit. AC contactor for the main contact is often open contact, auxiliary contacts are normally open contact and normally closed contact two. AC contactor contacts are bridge double breakpoint and finger type breakpoint and other types. The main contacts are generally made of unipolar or bipolar, due to contact with or disconnect the current is large, so the use of rolling contact finger contact. Auxiliary contact of the on-off current is small, often with point contact double break point bridge contact.
(3) arc extinguishing device Since the DC arc is not like the natural zero crossing of the AC arc, the main contact of the DC contactor is more difficult to arc when breaking large current (DC circuit), often producing a strong arc, Contact and delay power off. In order to quickly arc, DC contactor is generally used magnetic blowing arc extinguishing device, and equipped with partitions and clay arc cover. For the small-capacity DC contactor also has a permanent magnet to produce magnetic force, the large-capacity contactor is commonly used longitudinal seam arc extinguishing method. AC contactor of the arc extinguishing device has a grid plate arc, electric power arc, longitudinal seam arc, magnetic stripping arc, and several.
DC contactor working principle
When the contactor coil power, the coil current to produce magnetic field, so that the static core to produce electromagnetic suction suction core, and drive contact action: normally closed contact open, normally open contact closure, the two are linked. When the coil is powered off, the electromagnetic suction disappears, the armature in the release of the role of the release of the spring, the contact recovery: normally open contact open, normally closed contact closed.
In addition, the DC contactor to be used in the DC as the power circuit, than the DC pump, which is the power plant in the power failure when the turbine system to protect the motor, it is DC control, and its main circuit for the DC, auxiliary circuit Also for the DC, of course the contactor must also be DC.
AC power for power equipment, DC power for the control and protection of power equipment, as well as accident lighting. Like noise such parameters, I have seen the AC and DC contactors, are poor quality noise on the big. And internal resistance it, because the voltage level is different, so it is different.
DC contactor selection method
1. Selection of DC contactor type The type of DC contactor should be selected according to the type of load current and the severity of the load, that is, AC load or DC load, light load, general load or heavy load.
2. Rated current of the DC contactor main contact DC contactor The rated current of the main contact can be calculated according to the empirical formula. IN Main contact ≥PN motor / (1 ~ 1.4) UN motor If the DC contactor controls the motor start, Moving or reversing frequently, generally the contactor main contact rated current down to use.
3. Rated voltage of the main contact The voltage on the nameplate of the main contact is the rated voltage that the main contact can withstand. It is not the voltage of the suction coil. When used, the rated voltage of the contactor main contact should be not less than the rated voltage of the load.
4. Operation frequency selection The operating frequency refers to the number of times the contactor turns on and off every hour.When the on-off current is large and the on-off frequency is too high, it will cause the contact to be overheated and even welded. If the operating frequency exceeds the specified value , Should use the rated current level of the DC contactor.
5. Coil rated voltage selection coil rated voltage is not necessarily equal to the rated voltage of the main contact, when the line is simple, the use of electrical appliances, can be directly selected 380V or 220V voltage, such as complex lines, the use of electrical appliances more than 5h, available 24V, 48V Or 110V voltage (1964 international provisions for the 36V, 110V, or 127V) coil.
DC contactor function
DC contactors are mainly used for remote connection and breaking of DC circuits and frequent start, stop, reverse and reverse brake DC motors, also used to frequently turn on and off the lifting solenoid, solenoid valve, clutch Of the electromagnetic coil and so on. DC contactor with three-dimensional arrangement and flat layout of the two structures, and some products are based on the AC contactor derived. Therefore, the DC contactor structure and working principle and AC contactor is basically the same, mainly by the electromagnetic mechanism, contact system and arc extinguishing device composed of three parts.
DC contactor is a long-distance frequent and connected to the DC main circuit and large-capacity control circuit of the electrical appliances to vacuum for the arc medium, with a small size, high pressure, breaking capacity, long service life, Contact protection, especially because of its arc is not exposed, safe and reliable, etc., are widely used in mining, metallurgy, ship, subway, chemical, electric traction and other sectors of the DC circuit. The main control object is the motor, can also be used to control other power loads such as electric heaters, lighting, welding machines, capacitors and so on. The product is equipped with suitable operating mechanism, can be installed into high and low voltage AC vacuum contactor and high and low voltage AC vacuum circuit breaker arc extinguishing accessories for power distribution control, especially suitable for the composition of vacuum explosion-proof switch.
The choice of DC contactor, first of all depends on the application of the line control mode, the contactor in the line function, because the DC contactor main contact with a single point, single contactor is mainly used for power generation - electric system, or Other independent variable flow system, the function is: 1 ready, allowed to run. 2 accident state quickly cut off the main circuit. So the contactor rated current, rated voltage, arc breaking capability, must be satisfied with the system requirements. Double contact contactor is used: non-independent power supply system; reversible system, the same attention to the rated current, rated voltage, arc breaking capacity. Finally, the clutch coil voltage, to be attached to the operating system requirements, and then pull the coil is larger, to add RC absorption circuit, to prevent self-inductance potential breakdown itself, or related equipment.
DC contactor composition and structure
DC contactors are mainly used for remote connection and breaking of DC circuits and frequent start, stop, reverse and reverse brake DC motors, also used to frequently turn on and off the lifting solenoid, solenoid valve, clutch Of the electromagnetic coil and so on. DC contactor with three-dimensional arrangement and flat layout of the two structures, and some products are based on the AC contactor derived. Therefore, the DC contactor structure and working principle and AC contactor is basically the same, mainly by the electromagnetic mechanism, contact system and arc extinguishing device composed of three parts.
(1) Electromagnetic mechanism DC contactor Electromagnetic mechanism consists of iron core, coil and armature, etc., and more use around the angular rotation of the clutch structure. The shape of the armature movement of the rotation of the shaft and the linear motion of the straight-line, linear movement of the armature can be divided into straight-mounted direct and flip-type direct drive (that is, the contact in the electromagnetic mechanism below). As the coil is through the direct current, the normal work, the core will not produce eddy current, the core does not heat, no iron loss, so the core can be made of whole cast iron or cast steel. DC contactor coil turns more, in order to make the coil heat is good, usually the coil wound into a long and thin cylindrical. As the magnetic flux in the core is constant, there is no need for a short circuit ring on the pole surface. In order to ensure reliable release of the armature, often between the core and the armature pad with non-magnetic gasket to reduce the impact of remanence. 250A above the DC contactor is often used in series double winding coil, coil l for the start coil, coil 2 to maintain the coil, contactor of a normally closed contact with the holding coil in parallel. In the circuit just after the moment, the coil 2 is normally closed contact short circuit, the coil l can get a larger current and suction. When the contactor moves, the normally closed contact is disconnected, the coil 1 and the coil 2 are connected in series. Since the voltage is constant, the current is small, but the armature can be kept to be lifted to save power and extend the life of the solenoid the goal of.
(2) contact system DC contactor with main contacts and auxiliary contacts. The main contact is used to turn on and off the current circuit, which is the main load circuit. Therefore, the main contact cross-sectional area is large, generally flat type. Auxiliary contact cross-sectional area is small, generally spherical type, for turning on, disconnect the control circuit, signal circuit. AC contactor for the main contact is often open contact, auxiliary contacts are normally open contact and normally closed contact two. AC contactor contacts are bridge double breakpoint and finger type breakpoint and other types. The main contacts are generally made of unipolar or bipolar, due to contact with or disconnect the current is large, so the use of rolling contact finger contact. Auxiliary contact of the on-off current is small, often with point contact double break point bridge contact.
(3) arc extinguishing device Since the DC arc is not like the natural zero crossing of the AC arc, the main contact of the DC contactor is more difficult to arc when breaking large current (DC circuit), often producing a strong arc, Contact and delay power off. In order to quickly arc, DC contactor is generally used magnetic blowing arc extinguishing device, and equipped with partitions and clay arc cover. For the small-capacity DC contactor also has a permanent magnet to produce magnetic force, the large-capacity contactor is commonly used longitudinal seam arc extinguishing method. AC contactor of the arc extinguishing device has a grid plate arc, electric power arc, longitudinal seam arc, magnetic stripping arc, and several.
DC contactor working principle
When the contactor coil power, the coil current to produce magnetic field, so that the static core to produce electromagnetic suction suction core, and drive contact action: normally closed contact open, normally open contact closure, the two are linked. When the coil is powered off, the electromagnetic suction disappears, the armature in the release of the role of the release of the spring, the contact recovery: normally open contact open, normally closed contact closed.
In addition, the DC contactor to be used in the DC as the power circuit, than the DC pump, which is the power plant in the power failure when the turbine system to protect the motor, it is DC control, and its main circuit for the DC, auxiliary circuit Also for the DC, of course the contactor must also be DC.
AC power for power equipment, DC power for the control and protection of power equipment, as well as accident lighting. Like noise such parameters, I have seen the AC and DC contactors, are poor quality noise on the big. And internal resistance it, because the voltage level is different, so it is different.
DC contactor selection method
1. Selection of DC contactor type The type of DC contactor should be selected according to the type of load current and the severity of the load, that is, AC load or DC load, light load, general load or heavy load.
2. Rated current of the DC contactor main contact DC contactor The rated current of the main contact can be calculated according to the empirical formula. IN Main contact ≥PN motor / (1 ~ 1.4) UN motor If the DC contactor controls the motor start, Moving or reversing frequently, generally the contactor main contact rated current down to use.
3. Rated voltage of the main contact The voltage on the nameplate of the main contact is the rated voltage that the main contact can withstand. It is not the voltage of the suction coil. When used, the rated voltage of the contactor main contact should be not less than the rated voltage of the load.
4. Operation frequency selection The operating frequency refers to the number of times the contactor turns on and off every hour.When the on-off current is large and the on-off frequency is too high, it will cause the contact to be overheated and even welded. If the operating frequency exceeds the specified value , Should use the rated current level of the DC contactor.
5. Coil rated voltage selection coil rated voltage is not necessarily equal to the rated voltage of the main contact, when the line is simple, the use of electrical appliances, can be directly selected 380V or 220V voltage, such as complex lines, the use of electrical appliances more than 5h, available 24V, 48V Or 110V voltage (1964 international provisions for the 36V, 110V, or 127V) coil.
DC contactor function
DC contactors are mainly used for remote connection and breaking of DC circuits and frequent start, stop, reverse and reverse brake DC motors, also used to frequently turn on and off the lifting solenoid, solenoid valve, clutch Of the electromagnetic coil and so on. DC contactor with three-dimensional arrangement and flat layout of the two structures, and some products are based on the AC contactor derived. Therefore, the DC contactor structure and working principle and AC contactor is basically the same, mainly by the electromagnetic mechanism, contact system and arc extinguishing device composed of three parts.