Snap-in capacitors

Overview of Snap-In Capacitors and Their Mounting Requirements

Installation Precautions for Electrolytic Capacitors:

- Ensure the rated values (capacitance and voltage) of the electrolytic capacitors before installation.

- Confirm the polarity of the electrolytic capacitors before installation.

- Do not use capacitors that have fallen to the ground.

- Do not deform the capacitors during installation.

- Ensure that the terminal spacing of the capacitors matches the hole spacing on the PCB before installation.

- When installing snap-in type electrolytic capacitors, push them until they fit tightly with the substrate.

- When bending the leads of the electrolytic capacitors with an automatic insertion machine to fix them on the PCB, do not apply excessive force.

- Avoid impact forces caused by automatic insertion machines, assembly machines, suction devices, product inspection devices, and positioning operations.

- If concerned about vibration and impact during assembly, use auxiliary tools, adhesives, etc., to enhance the firmness of the capacitors on the PCB.

- The tightening torque of bolt terminals should not exceed the specified range in the product catalog and specification sheets.

Standard Lead Spacing for Snap-In Capacitors:

Electrolytic capacitors are common components in electronic circuits, and the lead spacing is a critical dimension, referring to the distance between the two leads. According to international standards, there are generally two lead spacing sizes for electrolytic capacitors: 2.5mm and 5mm. The 2.5mm lead spacing is typically used in low-power electronic devices and smaller circuit boards, while the 5mm lead spacing is used in high-power electronic devices and larger circuit boards.

Impact of Incorrect Lead Spacing:

Incorrect lead spacing can lead to several issues in PCB design, including:

- Short circuits

- Mechanical stress leading to component failure

- Inefficient soldering and assembly processes

- Overall reduced capacitor performance and longevity

Common Types of Capacitor Failures

Short Circuit: The resistance between the two terminals of the capacitor approaches zero, causing a short circuit.

Open Circuit: The resistance between the two terminals of the capacitor becomes very high, and the capacitor can no longer store or release charge.

Leakage: Defects in the insulating material cause leakage of direct current or continuous voltage through the capacitor.

Capacitance Drift: The capacitance value changes due to aging or damage, no longer meeting the specification requirements.

Visual Inspection

Signs of capacitor failure include:

1. Reduced capacitance.

2. Complete loss of capacitance.

3. Leakage in the circuit.

4. Short circuits.

If the capacitor casing is deformed or bulging, it indicates damage to the internal insulating medium or electrodes, and the capacitor should be immediately taken out of service and replaced.

Causes of Capacitor Popping

Several scenarios can lead to capacitor explosions:

1. Poor Manufacturing Process:Poor manufacturing can directly cause internal component breakdown and insulation damage of the casing.

2. Poor Sealing:Poor sealing allows external moisture to enter the capacitor, reducing insulation resistance and increasing the risk of explosion.

3. Severe Oil Leakage:In oil-filled capacitors, severe oil leakage lowers the oil level, leading to shell discharge or severe breakdown, both of which can cause explosions.

4. Prolonged Overvoltage Operation:Prolonged overvoltage operation accelerates insulation aging and decomposition, generating gas and increasing internal pressure, leading to bulging or explosion.

5. Reclosing with Residual Charge:Reclosing capacitors without complete discharge can cause explosion due to the voltage polarity being opposite to the residual charge.

Prevention and Maintenance

To avoid explosion failures in power capacitors, the following preventive measures are recommended:

1. Avoid Oil-Filled Capacitors:Oil-filled capacitors are more prone to issues like oil leakage and shell discharge. Dry-type, oil-free power capacitors are recommended for better safety.

2. Strengthen Inspection:Regular inspection of operating capacitors can detect early signs of failure, such as unusual noises or bulging, allowing for timely intervention.

3. Install Protective Devices:Use capacitors with built-in protection or add external protection devices to cut off faulty capacitors before they explode.

Snap-in capacitors are widely used in various industrial and commercial applications:

1. Industrial-grade variable frequency drives, servo controls, switching power supplies, PC power supplies, industrial power sources.

2. Welding machines, inverters, CNC machine tools, variable frequency power supplies, automotive electronics, electrical controls.

3. Energy storage welding machines, high-power UPS, communication power supplies, computer power supplies, electric vehicles, electric trains, variable frequency drives.

4. Professional audio equipment, amplifiers, automotive electronics.

5. Special electronic and electrical applications and other DC and pulsed circuits.