Specific Energy - The ratio of the energy output of a cell or battery to its weight (Wh/kg). This term is used interchangeably with gravimetric energy density.
COS phi - A measure of the phase shift between the current wave and the voltage wave observed at the terminals of a load supplied with AC power at a given frequency.
Crest factor (Fc) - Ratio between the peak current value to the rms current value.
Filter (phase-shift) - Filter used to reduce, if necessary, the overall distortion due to the current harmonics injected into the mains upstream of a UPS by its rectifier-charger. Filtering is superior to that of a traditional filter of the L or C type.
Internal Impedance - The opposition exhibited by a circuit element (cell or battery) to the flow of an alternating current (a.c.) of a particular frequency as a result of resistance, induction and capacitance.
IR Drop - A voltage drop associated with the electrical resistance (R) of a battery or current flow (I). The voltage drop is the product of the current (in amperes) and the resistance (in ohms).
Thevenin generator - For a given load, it is possible to consider the power supply as a voltage generator, referred to as a Thevenin generator, made up of a perfect voltage Uo generator, in series with an internal impedance Zs - n Uo is the voltage measured across the load terminals, given that the load is to be disconnected (load terminals forming an open circuit), n Zs is the equivalent impedance as seen from the load terminals (again considered an open circuit), obtained by short-circuiting the upstream voltage generator(s).
