Contactor problems, what are the common faults of AC contactors?

Contactor, which can be understood as a kind of switch.

The "main contact" of the contactor is actually a set of high-current main switches.

So, how does the contactor control the ON and OFF of this set of main switches?

It's up to the control end.

The so-called control end is actually an electromagnetic coil.

When an electric current is input into the coil, the electromagnet generates a magnetic force. This magnetic force attracts a block of iron.

And this iron block is actually connected to the "main contact".

Therefore, the whole process of action is like this:

When energized in the control coil is applied, the electromagnet generates suction. Attract iron blocks. Then the iron block drives the main contact action. The main contact is turned on or off the circuit.

The basic classifications of contactors mainly include:

Normally open, or normally closed.

Let me illustrate with an example: if you come across a normally open contactor, then it is clear that the main contact is originally off. When you control the coil is energized, the main contact is driven and becomes closed.

The long closed contactor, on the other hand, is just the opposite.

Generally speaking, the contactors you can see in the industry have two rows of contacts of "normally open" and "normally closed" on a contactor.

Next, when choosing, you should look at the rating. For example, voltage, current, and so on.

So it's not difficult.

Contactor contact is an automated control appliance.

The contactor is mainly used for frequent connection or disconnection of AC and DC circuits, with large control capacity, long-distance operation, with relays can achieve timing operation, interlocking control, various quantitative control and loss of voltage and undervoltage protection, widely used in automatic control circuits, its main control object is the motor, can also be used to control other power loads, such as electric heaters, lighting, welding machines, capacitor banks, etc.

Structural Composition:

The contactor is mainly composed of electromagnetic system, contact system, arc extinguishing system and other parts.

1. Electromagnetic system: The electromagnetic system includes an electromagnetic coil and a core, which is an important part of the contactor, relying on it to drive the closing and disconnection of the contact.

2. Contact system: The contact is the executive part of the contactor, including the main contact and the auxiliary contact. The function of the main contact is to turn on and break the main circuit and control the larger current, while the auxiliary contact is in the control loop to meet the requirements of various control methods.

3. Arc extinguishing system: The arc extinguishing device is used to ensure that the arc generated is reliably extinguished when the contact is disconnected from the circuit, so as to reduce the damage of the arc to the contact. In order to quickly extinguish the arc when disconnected, the contactor is usually equipped with an arc extinguishing device, which is generally a semi-sealed longitudinal seam clay arc extinguishing cover, and is equipped with a strong magnetic arc blowing circuit.

Normally open and normally closed contacts are often used in control lines for self-locking or interlocking control. The selection of contacts is based on actual needs. Some lines can meet the requirements with only normally open contacts, so there is no need for more contacts.

1. The main contact, mostly normally open contact, has a large current carrying capacity, and is mostly used to control motor start-up and other controls.

2 auxiliary normally open contacts, play an auxiliary role, can be used for self-locking, outgoing signals and other circuit requirements 3 auxiliary normally closed contacts, in complex circuits to achieve linkage, sometimes used as motor interlocking generally such as CHINT contactor, CJX2-6511, that is, the main contact is allowed to pass through the maximum current of 65A, there is 1 pair of auxiliary normally open contacts, a pair of auxiliary normally closed contacts, CJX2-3210 is the main contact allowed to pass through the current 32A, there is a pair of normally open contacts, there is no normally closed contact.

Different contactors can be selected according to different circuit requirements.

The first 1 represents the auxiliary normally open contact, 1 is present, and 0 is none.

The second 1 represents the auxiliary normally closed contact, which is also 1 with 0 no.

1. The iron core cannot be closed or the suction power is insufficient.

Cause of failure: the power supply voltage is too low or fluctuating too large, the power supply capacity of the operation circuit is insufficient or the wire is broken and the control contact is poor, the technical parameters of the coil are inconsistent with the use conditions, and the product itself is damaged.

Solution: Increase the power supply voltage, increase the power supply capacity, replace the line, repair the auxiliary contact, replace the contactor coil or contactor, and eliminate the stuck fault.

2. AC contactor.

The contacts do not release or release slowly.

Cause of failure: The contactor contact is burned, the mechanical suction part is stuck, and there is oil or dust on the pole surface of the core.

Solution: See whether the contactor contact is burned, if the contact is burned, replace the contact, and check whether there is any foreign matter on the pole surface of the core.

3. The AC contactor coil is overheated or burned.

Cause of failure: The contactor contact is burned, the mechanical suction part is stuck, and there is oil or dust on the pole surface of the core.

Solution: See whether the contactor contact is burned, if the contact is burned, replace the contact, and check whether there is any foreign matter on the pole surface of the core.

Fourth, the electromagnet of the contactor.

High noise (AC voltage).

Cause of failure: the power supply voltage is too low, the magnetic system is skewed or the mechanical part is stuck so that the core can not be flattened, the core is rusted or there are foreign objects, the short circuit ring is broken or the core is worn.

Solution: Increase the voltage of the operating circuit, adjust the magnetic system, check whether there is a foreign body in the core, and replace the core if there is a foreign body.

5. Contactor contact melting.

Cause of failure: The operation frequency is too high or the product is overloaded, and the load line is short-circuited.

Solution: Replace the AC contactor with higher power to eliminate the short circuit fault.

Common faults of contactors are:

After power-on, it cannot be closed or cannot be completely closed, because the voltage level of the coil is wrong or the voltage is insufficient, the moving parts are stuck in place, the contact overtravel is too large and the contact spring and the release spring reaction force is too large, etc.;

The suction process is too slow, the reason is that the air gap between the dynamic and static iron cores is too large, the reaction is too large, and the coil voltage is insufficient.

The reason for excessive noise or vibration is that the magnetic ring is broken, the coil voltage is insufficient, and there are dirt and rust spots on the core plate surface;

The coil is damaged or burned due to the internal disconnection of the coil or the short circuit between turns, the coil is running under overvoltage or undervoltage, etc.;

After the coil is powered off, the core is not released, the reasons are too large remanence, too little reaction force, sticky grease on the plate surface, and the moving parts are stuck in place;

The reason for the contact temperature rise is too high and the fusion welding occurs because the load current is too large, the overtravel is too small, the contact pressure is too small and the breaking capacity is insufficient, there are metal particles protruding or foreign matter on the contact surface of the contact, and the vibration is too intense or multiple vibrations occur during the closing process.

AC contactor is generally used to turn on or off the power supply in the control circuit of electromechanical equipment, it can frequently turn on or off the AC circuit, and can achieve long-distance control. The contactor is mainly composed of a contact system and an electromagnetic system. The fault of the AC contactor generally occurs in the first circle circuit, mechanical part and contact part.

AC contactors: three common faults and analytical treatment.

There are many common faults of AC contactors, such as 1If the voltage is too low, the contactor coil will be heated and burned out, and the voltage will be too low to cause the contactor copper core to be weak in sucking, and the copper core will emit an obsessive and entangled AC sound. 2.

The generation of AC sound may also be due to dirt on the contact surface of the copper core, which can be eliminated if it is clear. 3.Too much voltage can also burn out the coil.

4.The capacity of the contactor is too small, which will damage the contacts of the contactor, and a larger contactor needs to be replaced. 5.

If there is too much dust in the environment, the contactor will not be flexible, and then it is easy to produce AC sound.

There are four common faults. Refer to the following below:

1.After the coil is energized, the contactor does not move or behaves abnormally.

Mainly due to open coil control circuits; Damaged coils; The thermal relay does not reset after operation; The rated voltage of the coil is higher than the line voltage; Excessive spring contact pressure or excessive release spring pressure; The contact process is too large.

2.After the coil is de-energized, the contactor is not released or is released delayed.

The main reason is that in the magnetic system, there is no air gap in the column, and the remanence is too large. The surface of the contactor core is oily or oily after a period of use; The contact welding resistance is poor, and the contact current is large when the motor is started or the circuit is short-circuited.

3.The coil is damaged or damaged due to overheating.

This is mainly due to the fact that the operating frequency and power continuity of the circuit exceed the technical requirements of the product. The core surface is uneven or the air gap is too large; mechanical damage, jamming of the moving part; If the ambient temperature is too high, or the air is humid or contains corrosive gases, the coil insulation is damaged, and the installation position is replaced.

4.The electromagnet is too noisy.

Mainly due to excessive pressure of the contact spring, or excessive contact stroke; The connecting pin of the armature to the mechanical part is loose, or the clamping screw is loose to install the connecting pin.

Analysis of common fault causes and solutions of AC contactors:

According to the use of AC contactors in recent years, their frequent failures are as follows:

1. It cannot be closed after power-on.

Cause of failure: a. The coil power supply line is disconnected.

b. The coil itself is broken.

c. The starter button is not in good contact.

d. The rated voltage of the coil is higher than the line voltage.

e. Stuck between the contact and the wall of the arc extinguishing chamber or other movable parts and the motion guide rail or guide trough stuck solution measures:

a. Check the line, find out the breakpoint and deal with it.

b. Replace the coil that meets the requirements.

c. Clean and polish the contacts or replace the button.

d. Replace the coil with the same rated voltage.

e. Adjust the relative position of the parts that are stuck with each other and eliminate the cause of friction between them

a. The coil voltage is insufficient.

b. The core pole area is dirty or overworn, resulting in unevenness.

c. Short circuit ring breakage.

d. Loose clamping screws of moving or static iron cores.

e. Improper coordination of movable parts.

f. The reaction force is too large.

Solution: a. Adjust the coil voltage.

b. Clean the pole surface, and scrape and trim the core pole surface if necessary.

c. Replace the short-circuit ring with a new one.

d. Tighten the screws.

e. Adjust after identifying the fault.

f. Replace the appropriate spring.

3. Release the contactor immediately after releasing the start button.

Cause of failure: a. Poor contact of the auxiliary contact of the contactor.

b. Poor contact of the control circuit contact.

c. The wiring of the self-pin contact does not meet the requirements.

Solution: a. Clean the auxiliary contact or replace it with a new one.

b. Identify the contacts with poor contact and clean or replace them.

c. Check the wiring and re-wire.

4. The contactor moves too slowly.

Cause of failure: a. The gap between the dynamic and static cores is too large.

b. The installation position remains unchanged.

c. The coil voltage is insufficient.

d. The reaction force is too large.

Solution: a. Adjust the mechanical part to reduce the gap.

b. Reinstall according to the provisions of the product instruction manual or technical conditions c. Adjust the coil voltage to make it qualified.

d. Replace with a suitable spring.

5. The contactor will not be released after power failure.

Cause of failure: a. The reaction force is small.

b. The remanence is too large.

c. The grease on the pole surface of the contactor core is not wiped clean.

d. The movable part is stuck.

e. The dynamic and static contacts have been fused together.

f. There is an error in the wiring of the control loop.

Solution: a. Replace with a suitable spring.

b, c, wipe the grease clean.

d. Check and remove obstacles or adjust the position of parts that are stuck with each other, pry open the welded contacts or replace the contacts.

f. Use a multimeter to find the wrong wiring and re-wiring.

6. The contact is seriously heated.

Cause of failure: a. The load current is too large.

b. The contact is seriously corroded.

c. The contact is seriously damaged so that the contact surface is reduced, resulting in poor contact D. The overstroke is too small.

e. Insufficient contact pressure.

Solution: a. Identify the cause and take measures.

b. Clean the contactor.

c. Refurbish with a fine file, and replace the contacts if necessary.

d. Adjust the stroke to make it suitable.

e. Adjust or replace the spring.

7. The main contact is welded.

AC contactor is a kind of electromagnetic automatic switch, it is mainly used for long-distance control control power, frequent start of motors and other loads, is the most commonly used control appliances in the power system, it is easy to cause equipment and personal accidents when it fails, and must be eliminated. The following analyzes several different fault phenomena of AC contactors, and gives corresponding treatment methods.

Fault phenomenon cause analysis and treatment method.

1.After the coil is energized, the contactor does not operate or does not act normally;

2.The line diagram controls the circuit break, to see if the terminal is broken or loose, and if there is a broken wire, replace the corresponding wire. If there is any loosening, fasten the corresponding terminals;

3.If the coil is damaged, measure the resistance of the wire with a multimeter, if the resistance is , replace the coil;

4.The thermal relay is not reset after operation. If the resistance value between the two normally closed points of the thermal relay is measured by the resistance file of the multimeter, then the reset button of the thermal relay can be pressed;

5.The coil voltage rating is higher than the line voltage. Replace it with a coil that adapts to the voltage control line;

6.Excessive contact spring pressure or release spring pressure. adjust the spring pressure or replace the spring;

7.Button contacts or auxiliary contacts are poorly contacted, and the buttons are cleaned up or replaced accordingly;

8.The contact overtravel is too large. Adjust the contact overtravel.