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Capacitors, Supercapacitors

D14.6 - Current Stress Calculation and Optimal Selection of Bulk Capacitor in Motor Drive System with Single-Phase Uncontrolled Rectification

Thursday, March 26, 2026
12:00 PM - 1:45 PM CT
Location: Hemisfair Ballroom
Current RMS value is of much importance for the selection of electrolytic buck capacitors in single phase uncontrolled rectification motor drive systems. This work provides an analytical calculation approach to determining the current RMS value of the DC-link capacitor, which is different from conventional circuit simulation or numerical computation. A dimensionless variable k (proportional to 1/C) is defined to simplify the non-linear transcendental equations because k is near zero in engineering and Taylor approximation can be readily applied. With the elegant analytical expression of current RMS value, an optimal selection guide of electrolytic capacitors is also proposed to minimize the capacitors volume. Simulations and experiments are carried out to verify the calculation results with errors of less than 5%. A motor drive system is also built up to demonstrate the validity and rationality of the proposed capacitor section guidelines.