API Capacitors’s definition of terms, where applicable, are within the context of IEC 61071 (Power Electronics Capacitors) and IEC 61881 (Capacitors for Power Electronics used on Rolling Stock), summarised below:
Udc
dc voltage: The normal dc voltage that may be continually applied to the capacitor for a lifetime expectancy of 100,000 hours at 70°C ambient.
UN
Peak repetitive voltage: The maximum operating peak voltage of either polarity but of a non-reversing type wave form, for which the capacitor has been designed for continuous operation.
US
Peak non-repetitive voltage: A peak voltage induced by a switching or any other disturbance of the system which is allowed for a limited number of times and for durations shorter than the basic period.
It is specifically equivalent to the Vdrm (Ugto) of GTO devices for the GT and GC ranges of capacitors.
IMAX
Maximum current: The maximum rms current for continuous operation.
IP
Maximum peak current: The maximum current amplitude that occurs instantaneously during continuous operation. Equivalent to Î as defined in IEEC 61071.
IS
Maximum surge current: The admissible peak current induced by a switching or any other disturbance of the system which is allowed for a limited number of times.
R0
(See IEC 61071)
0amb
Cooling air temperature: The temperature of the cooling air measured at the hottest position in the bank, under steady state conditions, midway between two units. If only one unit is involved, it is the temperature measured at a point approximately 0.1 m away from the capacitor container and at two-thirds of the height from its base.
L
(See IEC 61071)
Rs
Associated series resistance that contributes to the I²R losses of the capacitor.