In normal work, the relay judges the input quantity (including light, electricity, etc.), and when it reaches a certain value, the output quantity jumps and changes, so that the control system and the controlled system are a kind of versatile control and protection. The components of the motor. In fact, the relay is an "automatic switch" that uses a small current to control a large current, so it can well complete the circuit's safety protection, automatic adjustment, and the like. Here are the common faults, overhauls and solutions for general relays.
Overhaul of common faults of relays
1. Overhaul of the sensing mechanism
For electromagnetic (voltage, current, intermediate) relays, the sensing mechanism is the electromagnetic system. The failure of the electromagnetic system is mainly concentrated in the coil and the moving and static core parts. Common faults and troubleshooting methods are:
(1) Coil troubleshooting
Coil faults are usually damaged by coil insulation; short circuit or grounding is caused by mechanical damage; because the power supply voltage is too low, the contact between the moving and static iron cores is not tight, so that the current flowing through the coil is too large, and the coil heats up and burns. When repairing, rewind the coil. If the armature does not pick up after the coil is energized, it may be that the coil lead-out line is disconnected, causing the coil to open. Check the drop off and solder it.
(2) Core troubleshooting
The iron core failure mainly has the armature that cannot be sucked up after being energized. This may be caused by a broken wire, a foreign object between the static iron cores, and a low power supply voltage. Repair should be done differently. After power-on, if the armature is noisy. This may be due to uneven contact surfaces of the moving and static cores or oil contamination. When repairing, remove the coil, level or smooth the contact surface; if there is oil, it should be cleaned.
2. Maintenance of the actuator
The actuators of most relays are contact systems. Through its "on" and "off", to complete certain control functions. Faults in the contact system generally include contact overheating, wear, welding, and the like. The main cause of contact overheating is insufficient capacity, insufficient contact pressure, surface oxidation or uncleaning; the main cause of increased wear is that the contact capacity is too small, the arc temperature is too high, and the contact metal is oxidized; The main reason for welding is that the arc temperature is too high, or the contact is severely beaten. The inspection sequence of the contacts is as follows:
(1) Open the cover and check the surface of the contact.
(2) If the surface of the contact is oxidized, the silver contact may not be repaired. The copper contact may be smoothed with a slick or a small knife to gently scrape off the oxide layer on the surface.
(3) If the contact surface is not clean, it can be cleaned with gasoline or carbon tetrachloride.
(4) If the contact surface has burn marks, the silver contacts may not need to be refurbished, and the copper contacts may be refurbished with a slick or a knife. It is not allowed to use sand cloth or sandpaper for refurbishment to avoid residual sand and cause poor contact.
(5) If the contacts are welded, the contacts should be replaced. If the contact capacity is too small, replace the relay with a larger capacity.
(6) If the contact pressure is not enough, adjust the spring or replace the spring to increase the pressure. If the pressure is still not enough, the contacts should be replaced.
3. Overhaul of the intermediate mechanism
(1) For time relays, the intermediate mechanism is mainly airbags. The common fault is that the delay is not allowed. This may be because the airbag is not tightly sealed or leaking, so that the action delay is shortened or even delayed; it may also be that the air passage of the airbag is blocked, so that the action delay becomes longer. When repairing, the former should be reassembled or replaced with a new airbag. For the latter, the air chamber should be dismantled to remove the blockage.
(2) For speed relays, the bakelite pendulum is an intermediate mechanism. If the motor can't brake and stop when the brake is reversed, it may be that the bakelite pendulum is broken. It should be replaced during maintenance.
Resolving common faults of relays
1, the contact loose back crack
The contact is the electrical contact part of the relay to complete the switching load. The contacts of some products are press-fitted by riveting. The main disadvantages are loose contact, cracked contact or excessive positional deviation. This will affect the contact reliability of the relay. The loosening of the erasing point occurs, which is caused by an unreasonable size of the mating portion of the reed and the contact or an improper adjustment of the riveting pressure by the operator. Contact cracking is caused by excessive material hardness or too much pressure. For different materials, the contacts are made of different materials. Some of the higher hardness contact materials should be annealed for contact manufacturing, riveting or spot welding. The manufacturing of the contacts should be careful. Since the materials have tolerances, the length of each cut should be determined after trial and error. Contact manufacturing should not result in flash, padding and underfill. The contact riveting is caused by the operator not correcting the touch and misaligning the upper and lower touches. Contact damage, contamination, oil contamination and iron filings on uncleaned tools. Regardless of the ills, it will affect the reliability of the relay. Therefore, in the process of contact manufacturing, riveting or electric welding, it is necessary to comply with the self-test regulations for the intermediate inspection and final inspection of the first piece to improve the assembly quality.
2, the relay parameters are unstable
A considerable part of the components of the electromagnetic relay is riveted and fitted, and the main problem is that the riveting is loose or the bonding strength is poor. This kind of fault will make the relay parameters unstable, the parameters change greatly under high and low temperature, and the mechanical vibration and impact resistance are poor. The main cause of this problem is the poor condition of the riveting parts, the improper placement of the parts, the unqualified quality of the work tools or the inaccurate installation. Therefore, it is necessary to carefully check whether the tool and the rivet parts meet the requirements before the welding.
3, electromagnetic system riveting deformation
After the riveting, the parts are bent, skewed, and the pier is thick and black, which makes the assembly or adjustment of the next process difficult, and may even result in scrapping. The main reason for this problem is that the riveted parts are too long, the force is not too short when the riveting is too short, the assembly deviation is wrong or the design size is wrong, and the parts are improperly placed. When riveting, the operator should first check the size of the parts, the appearance, and whether the tool is accurate. If the tool is not installed, it will affect the assembly quality of the electromagnetic system or the deformation of the core and the thickness of the pier.
4, glass insulator damage
The glass insulator is made of metal pins and glass sintered. It is easy to bend the pins during inspection, assembly, adjustment, transportation and cleaning. The glass insulators are dropped and cracked, resulting in leakage and insulation and pressure resistance. Rotation also causes the contact reed to shift, affecting the reliable continuity of the product. This requires the operator of the assembly to handle it lightly during the entire process of relay production. The components should be placed neatly in the transfer box. It is not allowed to pull or twist the lead when assembling or adjusting.
5, coil failure
There are many types of coils for relays, both outsourced and outsourced. The coils should be placed in separate special parts in separate parts. If the collisions are connected, the wires will be broken when separated. When the electromagnetic system is riveted, the pressure adjustment of the hand press and the press should be moderate. If the pressure is too high, the coil will be broken or the coil bob will be cracked, deformed, and the winding will be broken. If the pressure is too small, the winding will be loose and the magnetic loss will increase. Multi-winding coils are typically made with different colored leads. When welding, you should pay attention to the resolution, otherwise it will cause the coil to be soldered. The coils with the requirements of the beginning end are generally marked with the method of marking to indicate the beginning. Care should be taken when assembling and welding, otherwise the relay level will be reversed.