Example: You have two 80 V units connected in parallel. The load regulation effect due to currentsharing is 2.4 mV from the table above. The CV load regulation specification is 2 mV. Therefore, thetotal output voltage regulation effect is 2 mV + 2.4 mV, or 4.4 mV.Current Sharing EffectsThis section describes the current sharing effects of the paralleled units. These only affect theoperation of the paralleled units when operating near the current limit setting in voltage priority mode,operating near the voltage limit setting in current priority mode, or when using the low currentmeasurement range.In an ideal current sharing configuration, the total load current would be shared equally among allparalleled power supplies. For example, if you have three 1kW units connected in parallel and theload draws 75 A, each 1kW unit would contribute exactly 25 A to the total load current requirement.However, due to internal offset and gain differences among the paralleled units, there will be slightdifferences in the current being shared by the individual units. Normally this does not affect theoperation of the units or the total current being drawn by the load in any way. However, because ofthese slight sharing differences, the output current of an individual unit may bump up against thecurrent limit setting before the other units do. This will result in a current sharing fault (CSF), whichmeans that one of the units is no longer sharing current equally. The units will continue to sourcecurrent until the current limit setting of all units is reached. If the load current attempts to increaseabove the sum of the individual current limits, the paralleled units will be in constant current mode,with the output current being regulated rather than the output voltage.Another way that current sharing deviation can affect operation is when using the low currentmeasurement range on N7900 models. Current sharing deviations are greater as a percentage ofoutput current when operating at low current levels than when operating at high current levels. Thus,when operating at less than 10 % of the output current rating, the current sharing offset errorsbetween paralleled units may be large enough to cause an unexpected "Out of Range" measurementerror on the low current range. It is therefore recommended to leave the measurement range settingon Auto.Note that when current sharing, the algebraic sum of the contributed currents of the paralleled unitswill always equal the total current drawn by the load. To determine the total load current, you mustsum the output current readings of the individual paralleled units.If you need to determine what the worst case current deviation among paralleled units is, refer to theCurrent Sharing Tutorial.Keysight N6900/N7900 Series Operating and Service Guide 1734 Using the Advanced Power System
