# Technical Terms Related To Capacitors

- Rated Capacitance CR: The designed capacitance value, usually marked on the capacitor.

- Capacitance Tolerance : Admitted capacitance deviation from the rated capacitance at 20°C

- Rated Voltage UR: The maximum direct voltage or the maximum rms alternating voltage or the peak value of a pulse voltage which may be continuously applied to a capacitor at any temperature between the lower category temperature and the rated temperature.

- Category Voltage UC: The maximum voltage which may be continuously applied to a capacitor at its upper category temperature.

- Climatic category: The climatic category which the capacitor belongs to is expressed in numbers (standard IEC60068-1: example 55/85/21). The first number represents the lower category temperature; the second number represents the upper category temperature; the third number represents the number of days relevant to the damp heat test.

- Rated Temperature : The maximum ambient temperature at which the rated voltage may be continuously applied

- Upper Category Temperature: The designed maximum ambient temperature at which the capacitor can continuously operate.

- Temperature coefficient of capacitance: The change rate of capacitance with temperature measured over a specified range of temperature. It is normally expressed in parts per million per Celsius degree (10-6/ °C)

- Dissipation Factor: The ratio between the resistive and the reactive part of the impedance of the capacitor submitted to a sinusoidal voltage of specified frequency.

- Insulation Resistance/Time Constant: It is expressed in MO¸ measured after a minute of charge under a specified voltage.

- The time constant is expressed with the following formula: T= RC ( s )

The time constant of a capacitor equals to the product of the insulation resistance and the capacitance in value.