Aluminum Electrolytic Capacitor Selection Guide

Step 2 — Calculate Required Capacitance

Capacitance is determined by the required voltage ripple, load current, and switching frequency. For DC-link applications:

C = I × Δt / ΔV

Where: I = load current (A), Δt = hold-up time (s), ΔV = allowable voltage ripple (V). For rectified AC inputs, Δt is typically half the AC cycle period.

Step 3 — Check Ripple Current Rating

The capacitor's rated ripple current must equal or exceed the actual RMS ripple current in your circuit. Operating above the rated ripple current causes internal heating that reduces capacitor life exponentially. For high-ripple applications, select from our high ripple current series.

Step 4 — Evaluate Temperature & Lifetime

Capacitor life is halved for every 10°C increase in core temperature. Consider:

• Your equipment's maximum ambient temperature
• Temperature rise from ripple current self-heating
• Proximity to heat-generating components (transformers, heat sinks, IGBTs)
• Required service life (years of continuous or intermittent operation)

For extended life requirements, see our long life capacitor series.

Step 5 — Select Terminal Type & Case Size

Choose between:

• Snap-in terminal — For compact PCB mounting, automated assembly, applications up to 40φ diameter
• Screw terminal — For high-current connections, vibration-prone environments, and large case sizes (35φ–100φ)

Case size is determined by the capacitance/voltage combination and cooling requirements. Larger case sizes typically offer better thermal performance and longer life.

Step 6 — Review Special Requirements

Consider additional factors:

• Altitude derating — Above 2000m, voltage and ripple current ratings may need derating
• Vibration resistance — Screw terminal capacitors generally offer higher vibration tolerance
• Polarity protection — Ensure correct polarity in your circuit design
• Parallel/series operation — For higher capacitance or voltage, proper balancing resistors may be needed
• Regulatory compliance — RoHS, REACH, UL recognition if required