Alternating Current (AC) :This is the current drawn from the utility.

Direct Current (DC) : This is the current drawn from the battery.

Utility : This is the power from the service provider. In South Africa this is Eskom. In Tanzania this is Tanesco.

Power Factor (Pf): This is the ratio of apparent power to true power. Apparent power is VA and true power is watts.

Apparent power (VA) x Pf = True Power (watts)

Voltage Surge: This is when the utility rises by more than 10% for a short period of time (a few cycles)

Voltage Sag: This is when the utility decreases by more than 10% for a short period of time (a few cycles)

Transients (Spikes): These are rapid increases in voltage for a very short duration. Typically in excess of 400 volts (on a single phase 220 volt supply) for times of below 2 micro seconds.

Radio Frequency Interference (RFI): This is an electromagnetic signal that can disrupt electronic equipment.

Harmonics : A frequency that is a multiple of the fundamental frequency (50Hz in South Africa and Tanzania) eg 100Hz is the second harmonic.

Sine Wave : This is the voltage wave form generated by the utility supplier.

Quasi Sine Wave : . This is the output wave form of many Line Interactive UPS’s.

Crest Factor : This is the ratio of the peak value to the RMS value of a waveform. It is used to state the instantaneous overload that a UPS can accept.

Root Mean Square (RMS) : This value of voltage of current is 0.707 of the peak value of the wave form.

Peak : This is the maximum value that the sine wave reaches.

Prime Power : This is the maximum power that a genset can provide to run continuously.

Standby Power: This value is 10% higher than prime power. Gensets can normally run for 6-8 hours at this rating.

Photo Voltaic (PV) : This is the correct terminology for a solar panel.

Three Phase: Three individual voltage sine waves are produced simultaneously by the utility service provider 120 degrees apart.

Single Phase: The voltage between one of the phase voltages mentioned above and neutral.

Input to output voltage isolation: The input voltage and output voltage are not the same. (The input voltage is from the utility and the output voltage is from the inverter.)

A Cycle: This is the time taken for one Sine wave to be produced. In South Africa and Tanzania, this time is 20 mili seconds. 50 of these cycles occur in one second.