How to reduce contact arc ablation, the cause of contactor contact ablation

In addition to what was said upstairs, in fact, the contact (performance) of the contactor decreases after a long time, and poor contact will also cause ablative contact.

Since the voltage on the contact exceeds its rated voltage, it will arc when the contact is opened. Ablation of the contacts.

If the voltage increases, the arc extinguishing device or measure can not quickly extinguish the arc, resulting in arc pulling, and even can cause serious arc short circuit and electric shock ablation.

AC contactor contact ablation causes:

1. The load current is large and the action is frequent.

2. The contact (performance) of the contactor is reduced after a long time, and poor contact will also cause ablative contact.

Contactors are divided into AC contactors (voltage AC) and DC contactors (voltage DC), which are used in electricity, power distribution and consumption. Contactor in a broad sense refers to the electrical appliances that use the current flowing through the coil to generate a magnetic field and close the contact to control the load in industrial electricity.

The contactor should be used according to the characteristics of the decapitation, and the life is greatly reduced, the general contactor description has been used at different voltage levels, such as the 400V400A contactor of CJX2 in 720V to reduce the capacity to 250, because the breaking is the arc generated by the plasma is not easy to cool down under the original opening distance, and the insulating medium is not easy to recover.

Poor contact or burnout of the contact is due to the frequent operation of the contactor, and the arc ablates the contact to deform it or burn the contact surface. The solution is: remove the dynamic and static contacts (pieces), polish them with fine sandpaper, then check them for intangible changes, correct them with pliers and reinstall them, and simulate the suction state to check whether the contacts are well closed.

If there is still a gap, use pliers or screwdrivers to continuously adjust while observing until the dynamic and static contacts are tightly connected, and then energize the test several times to ensure that each contact does not flash at the moment of suction.

The AC contactor contact is easy to stick mainly caused by frequent action arcing, especially when ordinary lathes are threaded, frequent forward and reverse arc pulling causes contact ablation, and the improvement can be considered to replace the high quality, the current level is slightly larger, and the operation should also improve the habits.

There is no good way to use a pure resistive load, it is recommended to increase the contact power or use a contactor-type intermediate relay.

With inductive loads, freewheeling diodes can be connected in parallel at both ends of the load to reduce arcing.

Switch to relays with high-power contacts, or use contactless DC solid-state relays or high-power transistors or MOSFETs.

Contacts are used to turn on circuits, and when the contacts are tightly bonded, the circuits are turned on, and when they are separated, the circuits are disconnected.

Sometimes, there is an arcing phenomenon between the contacts and the contacts, and there is an electrical solitary between the contacts (often accompanied by sound, such as a slight zziz). There are many reasons for this, such as incomplete contact astomosis of the contacts, small contact surfaces, and contamination of the surface. Arcing is something we don't want to see, because it means high temperatures and ignition, which will reduce the service life of the contacts and even burn out the contacts.

Solve the arcing problem of relays: parallel RC absorption and DRC absorption circuits, and dissipate this part of the energy through resistance, which is also a more common method, but will delay the switching time.

The reason for the arc pulling of the relay contact is due to the inductive load in the circuit controlled by it, because the current of the inductor will not change abruptly, and at the moment when the switch is disconnected, the electromagnetic energy needs to rely on the breakpoint to generate self-inductive high voltage to break down the air to maintain the current, so as to generate an arc, and release energy through the thermal energy of the arc, and the magnitude of the high voltage generated by the self-induction is determined by the rate of change of the magnetic field. So the greater the magnetic field energy of the load, the greater the arc will be.

Relay is a kind of electrical control device, which is an electrical appliance that makes a predetermined step change of the controlled quantity in the electrical output circuit when the change of the input quantity (excitation quantity) reaches the specified requirements. It has an interactive relationship between the control system (also known as the input loop) and the controlled system (also known as the output loop).

Usually used in the control circuit of automation, it is actually a kind of "automatic switch" that uses a small current to control the operation of a large current. Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit.

The reason for the arc pulling of the relay contact is due to the inductive load in the circuit controlled by it, because the current of the inductor will not change abruptly, and at the moment when the switch is disconnected, the electromagnetic energy needs to rely on the breakpoint to generate self-inductive high voltage to break down the air to maintain the current, so as to generate an arc, and release energy through the thermal energy of the arc, and the magnitude of the high voltage generated by the self-induction is determined by the rate of change of the magnetic field. So the greater the magnetic field energy of the load, the greater the arc will be.

Workaround:

Parallel RC absorption and DRC absorption circuits dissipate this part of the energy through resistance, which is also a more common method, but it will delay the switching time.

Arc suppression, such as arc suppression hood, etc. However, most of these are suitable for switches with large capacities, such as AC contactors, ACB switches, oil switches, etc.

Contactless switch replacement. Such as thyristor, transistor, MOS tube, IGBT tube, etc. These power devices also need to be protected by absorption loops.

At present, some power control switches, and some use bidirectional thyristors combined with switch contacts to automatically control the thyristor at the moment of opening and closing to protect the power switch contacts. Consider it if necessary.

1. Connect the RC series circuit in parallel on the relay contact. 2. Limit the voltage by connecting a varistor in parallel on the relay contact. 3. Connect bidirectional thyristors in parallel on the relay contacts.

The electronic circuit is designed so that the thyristor is turned on when the relay contact is not broken, and the thyristor current is turned off naturally after the relay contact is broken. The thyristor is turned on through zero before the relay contacts are closed, and then the relay contacts are closed again. View the original post

1. The current contactor contacts are easy to stick, first of all, it is necessary to check whether the load has exceeded the capacity of the contactor, and then use the circuit protection contact when determining that the contactor capacity is indeed greater than the load power.

2. The damage to the contacts is mainly caused by arc ablation. In order to reduce arc generation, varistor elements can be connected at both ends of the contact, which can significantly reduce the generation of arcing and greatly increase the service life of the contactor.

Use AC contactors that are 2 times or more of the load current rating.

When the contactor solenoid coil is not energized, the reaction force of the spring and the self-weight of the armature core keep the main contact in the open position. When the electromagnetic coil is connected to the control voltage (generally the rated voltage) through the control loop, the electromagnetic force overcomes the reaction force of the spring and draws the armature to the static iron core, driving the main contact to close, turning on the circuit, and the auxiliary contact acting accordingly.

The arc extinguishing device is used to ensure that the arc generated when the contact is disconnected from the circuit is reliably extinguished, and 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.

The AC contactor contact is easy to ablation and adhesion is caused by the small capacity of the AC contactor applied, and it is advisable to choose an AC contactor with 2 times or more of the load current rating, and the contact is more durable.

There is no way to protect the contact There are several reasons for contact adhesion: 1. Low voltage: the contact is closed and does not die, and it is illuminated into adhesion, 2 phase wires are directly glued to ground, 3. The load capacity of the contactor is lower than the load.

There are many reasons for the adhesion of contactor contacts, some of which are small in capacity and replaced with a larger one. Some start frequently, and it is a good idea to change to a larger one. Yours is running under what load and under what circumstances. Let's see if I can think of a good solution for you.

In the parallel resistor-capacitance arc suppression circuit at the switch contact, the resistance and capacitance value needs to be determined according to the current and inductance in the actual circuit.

This is very dangerous. If the moving contact has all left the static contact, the arc has been pulled at this time, the contact may have been ablated, and then close it will not be in good contact, and may have been pulling the arc, so you can only pull the scalp as quickly as possible, hoping that the arc can be naturally extinguished after pulling the arc for a while. Pay attention to personal safety.

This disconnector is definitely unusable and needs to be replaced.

At this time, an arc has been generated between the contacts, and if the arc is allowed to burn, the consequences will be serious. Therefore, I think it is better to close it quickly to avoid the accident from expanding. Then immediately disconnect the circuit breaker on the line, and overhaul the disconnector after a power failure. It's just strange, why didn't the interlocks work?

The total current in the circuit decreases. ( Three-phase asynchronous motor with rated load torque controls the operation signal, all high-voltage disconnectors of relays and automatic devices when the moving knife is broken from the static contact.)

It can't be helped, people are lucky if they are fine.