The distinction between AC and DC contactors depends essentially on whether the load end is used for AC or DC. Now there is a part of the AC contactor control coil is DC, the suction electromagnet is also DC electromagnet, easy to cause some people’s misunderstanding, in fact, this contactor should be called DC control AC contactor or AC contactor nature. Such as ABB BC6 series, Shanghai Huatong HAC6 series and so on.
Based on this, the AC contactor controlled by DC can replace the AC contactor controlled by AC as long as the circuit type of the control circuit is changed, such as replacing AC with DC. But you can’t replace a contactor with an AC load and a DC load.
An AC low-voltage contactor works on the same principle as a DC contactor, except that the suction coil of an AC low-voltage contactor is powered by an AC power supply, while the suction coil of a DC low-voltage contactor is powered by a DC power supply. In addition, because the coil of the DC low-voltage contactor is direct current, and the direct current has no instantaneous value, the effective value at any moment is the same, without zero crossing. When the coil of DC low-voltage contactor is energised, the coil current generates a magnetic field, which makes the static iron core generate electromagnetic suction to attract the moving iron core, and drives the contact action. The dynamic break contact is disconnected, and the dynamic contact is closed. The two are linked. When the coil is power off, the electromagnetic suction disappears, the armature is released under the action of the release spring, so that the contact is restored.
Low voltage dc contactor is composed of dc, which is used in the field of long-distance frequently on and subsection of rated voltage 400 v, rated current 630 a dc power line and large capacity of control circuit of electric equipment, generally is a group or groups of two main contactor, rather than the ac contactor’s main contact for the three groups, it for vacuum arcing medium, With small volume, high voltage resistance, strong breaking ability, long service life, contact maintenance free, especially because of the arc is not exposed, safe and reliable and other advantages, widely used in mining, metallurgy, shipbuilding, subway, chemical industry, electric traction and other departments of the DC circuit.
The main control object of the DC low-voltage contactor is the positive and negative rotation, start, stop and brake of the DC motor. It can also be used to frequently connect and disconnect the electromagnetic coil of the lifting electromagnet, solenoid valve and clutch, etc. It can also be used to control other power loads, such as electric heats, lights, welders, capacitors, etc. DC contactor with appropriate operating mechanism, can be installed as high and low voltage AC vacuum contactor and high and low voltage AC vacuum circuit breaker arc extinguishing accessories, used for power distribution control, especially suitable for the formation of vacuum flameproof switch.
The DC contactor has the following characteristics:
1. The moving core and the static core are made of whole solid material, rather than silicon steel sheet;
2, the voltage coil has a large direct current resistance value;
3, according to the load and control requirements, installed with DC main contacts and the number of different auxiliary contacts, the main contacts with arc extinguishing device, some without arc extinguishing device.
Since the current through the suction coil is direct current, the current through the coil will not produce eddy current to the iron core during operation, so the iron core will not be heated, so it has no iron loss, so the iron core can be made of integral cast iron or cast steel.
