What are the characteristics and selection methods of DC contactors

Update:19-06-2020
Summary:

The DC contactor adopts a modular design, which can ass […]

The DC contactor adopts a modular design, which can assemble the number of contact paths required by the customer and the form of contacts required by the customer (normally open, normally closed and converted) with the fewest parts; the contact breaking voltage of this series of products is high , And the use of transverse magnetic field to extinguish the arc, the highest breaking voltage can reach 220VDC. The product is suitable for program-controlled power supply or uninterruptible power supply system, forklift, electric vehicle, engineering machinery system.
Advantages of DC contactors:
1. Reliable sealing allows the product to be used for a long time in harsh and explosion-proof environments. Its coils, contacts and other internal components are not oxidized. At the same time, the product has the advantages of low energy consumption, low heat generation, long life, small size and light weight. .
2. Can control high voltage and large current
3. Energy saving Some products of different specifications use energy saving plates.
4. The smaller arc makes the product more effective and safer when used. The inert gas seal is adopted so that when the product is in operation, there is basically no arc between the contacts, and the magnetic blowout is used to ensure safety.
5. High stability The internal mechanism and structure are completely sealed in inert gas, which is not disturbed by external bad factors, and the contact resistance remains stable for a long time.
6. A wide range of applications include: DC power control, battery switch control, circuit safety protection, etc.
Working principle of DC contactor:
When the contactor coil is energized, the coil current generates a magnetic field, which causes the static iron core to generate electromagnetic attraction to attract the moving iron core and drive the AC contactor
Contact action: normally closed contact is opened, normally open contact is closed, the two are linked. When the coil is de-energized, the electromagnetic suction force disappears, and the armature is released under the action of the release spring to restore the contacts: normally open contacts are opened, normally closed contacts are closed

Selection method of DC contactor:
1. Select the type of DC contactor The type of DC contactor should be selected according to the type of load current and the weight of the load, that is, whether it is an AC load or a DC load, whether it is a light load, a general load, or a heavy load.
2. The rated current of the main contact of the single-phase relays can be calculated according to the empirical formula of the IN main contact ≥PN motor/(1~1.4)UN motor if the motor controlled by the DC contactor starts, brakes or Frequent reversal, generally reduce the rated current of the main contactor of the contactor by one level.
3. Rated voltage of the main contact The voltage marked on the nameplate of the contactor refers to the rated voltage that the main contact can withstand, not the voltage of the attraction coil.The rated voltage of the main contact of the contactor should not be less than the rated voltage of the load during use.
4. Selection of operating frequency The operating frequency refers to the number of times the contactor is switched on and off per hour. When the on-off current is large and the on-off frequency is too high, it will cause the contact to overheat or even weld. If the operating frequency exceeds the specified value, it should be Choose a DC contactor with a higher rated current.
5. Selection of the rated voltage of the coil The rated voltage of the coil is not necessarily equal to the rated voltage of the main contact.When the circuit is simple and the number of electrical appliances is small, the voltage of 380V or 220V can be directly used.If the circuit is complex, the electrical appliances are used for more than 5h, and 24V, 48V or 110V can be used Voltage (36V, 110V, or 127V internationally in 1964) coil.