Capacitor Discharge Time Requirements

Article 460 covers the installation of capacitors on electrical circuits.

July 31, 2014

The residual voltage of a capacitor, rated not over 600V, shall be reduced to 50V or less within _____ after the capacitor is disconnected from the source of supply.

a) 15 seconds
b) 45 seconds
c) 1 minute
d) 2 minutes

See answer and applicable Code reference

The correct answer is: c) 1 minute

Article 460 covers the installation of capacitors on electrical circuits. As noted in Sec. 460.6, "Capacitors shall be provided with a means of discharging stored energy. In addition, as per 460.6(A), "The residual voltage of a capacitor shall be reduced to 50V, nominal, or less within 1 minute after the capacitor is disconnected from the source of supply."