How to select an AC source power rating for an application

Use the following information for selecting an AC Source that is appropriate for the application.

Specification	Description
Pout:	The maximum possible output power of the power supply
Eff:	The efficiency of the power supply
PF:	The input power factor of the power supply
Vin_low:	The minimum input voltage
CF_I:	The crest factor of the power supply’s input current
Ipk_need:	The repetitive peak current needed from the power supply
Ipk_ac:	The repetitive peak current that the AC source can provide
CF_ac:	Crest factor defined in the AC source
Irms_ac:	AC source’s maximum output R.M.S. current of the respective voltage range

Select an AC source with a power rating for which Ipk_ac is greater than Ipk_need

Ipk_need = Pout / Eff / PF/ Vin_low ) x CF_I

Ipk_ac = Irms_ac ( range of Vin_low ) x CF_ac

Example:

Assume: Pout = 300 W, Eff = 0.7, PF = 0.55, Vin_low = 90 V, CF_I = 4;

Ipk_need = (300/0.7/0.55/90)x4 = 35A

Given the above, the repetitive input current required will be 35A.

(35/3) x 90 = 1,050

If the AC source outputs CF_ac = 3, then the user must select an AC source which is able to deliver 11.7 Arms current under 90 V output. Therefore the user should use a 1,200VA AC source to test for this requirement.