Common Fault Detection and Troubleshooting Methods for Relays

A relay is one of the most commonly used actuating elements in electronic equipment. It is an electronic control device with a control system (also known as the input circuit) and a controlled system (also known as the output circuit). It is typically used in automatic control circuits and is also found in communication equipment such as PCM devices. In essence, it is an "automatic switch" that uses a smaller current to control a larger current. Therefore, it plays roles such as automatic regulation, safety protection, and circuit switching in circuits. The following mainly analyzes several common relay faults and their troubleshooting methods:

I. Loose or cracked contacts
Contacts are the electrical contact components that enable a relay to switch loads. The contacts of some products are secured by riveting or press-fitting. The main defects include loose contacts, cracked contacts, or excessive dimensional or positional deviation. These issues affect the contact reliability of the relay. Loose contacts are caused by unreasonable dimensions in the mating area between the spring leaf and the contact, or improper adjustment of the riveting pressure by the operator. Cracked contacts result from excessive material hardness or excessive pressure. For contacts made of different materials, different process techniques should be adopted. Some contact materials with high hardness should be annealed before contact manufacturing, riveting, or spot welding. Contact manufacturing should be carried out with care, as material tolerances exist; therefore, the cutting length for each batch should be determined after trial cutting. Contact manufacturing should not produce burrs, indentation damage, or incomplete filling. Off-center contact riveting is caused by the operator failing to align the mold correctly or by misalignment between the upper and lower molds. Contact damage or contamination is caused by oil contamination and metal chips on the mold that have not been cleaned. Regardless of the defect type, the operational reliability of the relay will be affected. Therefore, during contact manufacturing, riveting, or spot welding, the self-inspection procedures of first-article inspection, in-process sampling, and final inspection must be followed to improve assembly quality.

II. Unstable relay parameters
A considerable portion of the components of electromagnetic relays are secured by riveting. The main issue is looseness at the riveted joints or poor bonding strength. This defect causes unstable relay parameters, significant parameter variations under high and low temperatures, and poor resistance to mechanical vibration and shock. The main causes of this defect are out-of-tolerance riveted parts, improper part placement, substandard tooling quality, or incorrect installation. Therefore, before riveting or welding, the tooling and parts to be riveted should be carefully inspected to ensure they meet the requirements.

III. Deformation of riveted electromagnetic system components
After riveting, parts may become bent, twisted, or upset, which creates difficulties for subsequent assembly or adjustment and may even result in scrapping. The main causes of this defect include parts that are too long or too short, uneven force applied during riveting, tooling assembly deviations or design dimensional errors, and improper part placement. During riveting, the operator should first check the dimensions, appearance, and tooling of the parts for correctness. If the tooling is not properly seated, it will affect the assembly quality of the electromagnetic system or cause core deformation or upsetting.

IV. Damage to glass insulators
Glass insulators are formed by sintering metal pins with glass. During inspection, assembly, adjustment, transportation, and cleaning, issues such as bent pins, chipped or cracked glass insulators are prone to occur, which can cause air leakage and degrade insulation and withstand voltage performance. Pin rotation can also cause displacement of the contact spring leaf, affecting the reliable make-and-break of the product. This requires assembly operators to handle the product with care throughout the entire relay production process. Parts should be neatly arranged in transfer boxes. During assembly or adjustment, bending or twisting of the lead pins is not permitted.

V. Coil faults
Relay coils come in many types, some with outer wrapping and some without. Coils should be stored individually and separately in dedicated containers. If they collide or become entangled, separating them may cause wire breakage. During riveting of the electromagnetic system, the pressure of the manual press or power press should be adjusted appropriately. Excessive pressure can cause coil wire breakage, coil frame cracking or deformation, or winding breakdown. Insufficient pressure can cause loose winding and increased magnetic loss. Multi-winding coils generally use leads of different colors to identify the start ends. During soldering, care should be taken to distinguish them; otherwise, the coils may be soldered incorrectly. For coils with specific start and end requirements, marking methods are generally used to indicate the start and end terminals. Attention should be paid during assembly and soldering; otherwise, the relay polarity may be reversed.