CapXon UJ series aluminum electrolytic capacitors

CapXon UJ series aluminum electrolytic capacitors

Introduction: When the aging of aluminum electrolytic capacitors threatens the reliability of the system

High voltage aluminum electrolytic capacitors are one of the most vulnerable components in the output filtering circuits of industrial frequency converters, server power supplies, automotive charging modules, and various switch power supplies. Engineers often face scenarios where a device that has been running for many years experiences increased output ripple, decreased power efficiency, and even frequent protection restarts. Upon disassembly, it is discovered that the top of the capacitor is bulging or leaking. Even more tricky is that the prototype capacitor may have been discontinued (EOL), or the original factory specifications may be difficult to find, making it impossible to accurately select a replacement.

The UJ series standard Snap in aluminum electrolytic capacitors launched by CapXon are designed as a solution to meet harsh application environments. This series is specifically optimized for working conditions at 105 ° C high temperatures, with rated voltages covering 200 V to 500 V DC, capacitance values ranging from 82 µ F to 3300 µ F, and providing 2000 hours of durability and 5000 hours of useful life. Additionally, an AEC-Q200 certified version is available to meet automotive grade reliability requirements. This article will deeply analyze the technical parameters, selection methods, life assessment, and common troubleshooting of the UJ series from a practical perspective, helping hardware engineers make optimal decisions when replacing old capacitors or designing new ones.

Product Series Overview: Core Features and Applicable Scenarios

2.1 Overview of Basic Specifications

Performance indicators for parameter items

Working temperature range -40 ℃~+105 ℃

Rated voltage (VR) 200 V, 250 V, 350 V, 400 V, 450 V, 500 V DC

Capacitor range (CR) 82 µ F to 3300 µ F (depending on voltage)

Capacitor tolerance ± 20% (120 Hz/20 ℃)

When the surge voltage (VS) VR is ≤ 315V, VS=1.15 × VR; when VR>315V, follow the standard

Leakage current (ILEAK) ≤ 3 × √ (CR × VR) [µ A] (after applying rated voltage for 5 minutes)

Loss tangent (tan δ) ≤ 15% at 200-400V (120 Hz/20 ℃)

Durability: 105 ℃/2000 hours (applied with rated voltage and ripple current)

Useful Life: 105 ℃/5000 hours (with rated voltage and ripple current applied)

Vibration test at 10~55 Hz, amplitude 0.75 mm, 2 hours on each axis, 10g force

Why choose UJ series?

Compared to conventional capacitors at 85 ℃ or 105 ℃/2000 hours, the UJ series has significantly improved in the following aspects:

Higher heat load capacity: 5000 hours of useful life means that at the same temperature, the degradation rate of capacitors is more than 60% lower than that of ordinary products, greatly extending the equipment maintenance cycle.

Stable loss tangent: Within the entire rated voltage range, tan δ is only 15% (maximum), which is beneficial for reducing self heating.

Extremely low leakage current: The formula ILEAK ≤ 3 ·√ (C · V) is much lower than some older capacitors (which may require 6 ·√ (C · V)), especially suitable for high impedance circuits or holding circuits.

AEC-Q200 optional: For automotive applications such as on-board chargers (OBC), DC-DC converters, and electric power steering, the UJ series can provide a stress tested version to ensure reliability under extreme temperature cycling and vibration.

In depth interpretation of key electrical parameters

3.1 Rated voltage and surge voltage

In practical applications, the voltage borne by capacitors may briefly increase due to power transients. The UJ series specifies the surge voltage VS:

When the rated voltage VR is ≤ 315 V, VS=1.15 × VR

For models with a voltage of 350 V and above, it is usually done according to 1.1 × VR or following IEC standards.

For example, a 250 V UJ capacitor can withstand a surge of 287.5 V for 30 seconds (according to standard requirements). The 400 V model can withstand a surge of approximately 440 V. This provides valuable transient margin for engineers, especially in situations where there are unresponsed spikes on the DC bus.

3.2 Capacitor Tolerance and Temperature Characteristics

The tolerance of the UJ series is ± 20% (20 ℃/120 Hz), which is a common level for electrolytic capacitors. However, it should be noted that the capacitance value will significantly decrease with decreasing temperature. The low-temperature characteristic table provides the impedance ratio Z:

For the 200-250 V model, Z (-25 ℃)/Z (+20 ℃) ≤ 4, Z (-40 ℃)/Z (+20 ℃) ≤ 7.

This means that at -40 ℃, the equivalent series resistance (ESR) of the capacitor will increase several times, leading to an increase in ripple voltage. If the device operates outdoors in cold weather (such as charging stations in the north), it must be used with a reduced ripple current or a larger capacity capacitor must be selected.

3.3 Engineering significance of leakage current

The leakage current formula for the UJ series is ILEAK ≤ 3 ·√ (C · V) (µ A). Example:

470 µ F/400 V capacitor: ILEAK ≤ 3 ·√ (470 × 400)=3 ·√ 188000 ≈ 3 × 433.6=1300 µ A=1.3 mA.