![]() ![]() KWh: This is a measure of energy that includes time, or how much power has been delivered for how long. period at any time during the billing cycle. It is based on the highest usage over a 15-30min. Demand Charge (Peak Demand) The part of a bill for electric power based on the amount of power that the customer requires to be kept available to him. There are some utilities now charging for kva. We typically do not measure our THD since it is mostly driven by the quality of the building s AC power delivery rather than the charger itself.ΔΆ Buying AC power from utilities: Most facilities buy real power and pay a demand charge as well as a power factor fee if their power factor is low. 0.0% is perfect and a number over a few percent is considered poor. ![]() Input THD Total Harmonic Distortion is a measure of how well the power is both used and delivered to the charger. Our Equinox product had this type of module, but all other chargers do not. Our HF chargers are > 0.95 and our SCR chargers have power factor as low as.65 depending on battery size and charger ratings Power factor correction An electronics module that creates a better power factor with a combination of diodes, IGBT s, and magnetics (inductors). This would be read as power factor is real power over total power. Typical utilities start to add fees when the PF is less than Power factor equation: PF = kw / kva. ![]() kva = (kw 2 + KVAR 2 ) Power Factor (PF): A value from zero to one that explains the amount of real power out of the total power. Total Power (kva): also called apparent power. Ferro - ~80% SCR - ~85% HF - ~93% AC power: Real Power(Watts and kw): Also called: Active Power and Actual Power For three phase kw = Voltage L-L * Line Current * 1.73 *.001 * PF For single phase: Vac x Iac x PF Example (480 x 10 x.9)/1000 = 4.32Kw Reactive Power (KVAR): Power that does not contribute to charging batteries. For a three phase charger, it is necessary for a single meter to measure all 3 phases simultaneously in order to account for the relative phase relationships and get an accurate measure of real power. This is typically expressed as a percentage. Efficiency: Output Power divided by real power input. Output Power (Watts and kw): Watts(W) = Voltage X Current Kilo Watts(kW) = (Voltage X Current) X.001 Note: These equations are valid only for DC. Current: The rate of flow of electric charge measured in Amps. 1 Ametek Prestolite Power AC power / Charger / Battery terms Basic Values: Voltage: The potential difference at the battery (DC) or at the charger input (AC) measured in Volts. ![]()
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