When replacing a capacitor, which rating must be met or exceeded?

When replacing a capacitor, which rating must be met or exceeded?

• A. Current rating
• B. Voltage rating
• C. Capacitance value
• D. Temperature rating

Answer: (B)

The key requirement when replacing a capacitor is that its voltage rating must meet or exceed the highest voltage the circuit will apply to it. The voltage rating represents the maximum voltage the dielectric can withstand without breaking down. If a capacitor is exposed to higher voltage than its rating, the dielectric can fail, leading to leakage, shorting, overheating, or venting—and the circuit can fail or become dangerous. To be safe, choose a capacitor with a voltage rating at least equal to the system’s maximum operating voltage plus any possible transients or surges (for AC, use the peak voltage and account for spikes). The current rating, while important for handling ripple current and preventing overheating, does not set the voltage limit. The exact capacitance value must match the circuit’s needs (timing, filtering, etc.), because changing it alters how the circuit behaves. The temperature rating matters for reliability and derating in hot environments, but it does not define the voltage tolerance; in practice you still ensure the voltage rating is adequate while considering temperature effects for long-term reliability.

The key requirement when replacing a capacitor is that its voltage rating must meet or exceed the highest voltage the circuit will apply to it. The voltage rating represents the maximum voltage the dielectric can withstand without breaking down. If a capacitor is exposed to higher voltage than its rating, the dielectric can fail, leading to leakage, shorting, overheating, or venting—and the circuit can fail or become dangerous. To be safe, choose a capacitor with a voltage rating at least equal to the system’s maximum operating voltage plus any possible transients or surges (for AC, use the peak voltage and account for spikes).

The current rating, while important for handling ripple current and preventing overheating, does not set the voltage limit. The exact capacitance value must match the circuit’s needs (timing, filtering, etc.), because changing it alters how the circuit behaves. The temperature rating matters for reliability and derating in hot environments, but it does not define the voltage tolerance; in practice you still ensure the voltage rating is adequate while considering temperature effects for long-term reliability.