Design, Construction, and Performance Evaluation of a Variable AC and DC Power Supply System for Electrical Engineering Laboratories

This study presents the design, construction, and performance evaluation of a variable AC and DC power supply system for electrical engineering laboratory applications. The system was developed to provide a cost-effective and locally maintainable alternative to expensive commercial laboratory power supplies. It consists of a 2 kVA autotransformer for variable AC output, a full-wave bridge rectifier, filter capacitors, and protection and cooling units. The developed system delivers an adjustable AC output of 0–300 V and a corresponding DC output of up to approximately 422 V. Performance evaluation was conducted under different loading conditions to assess voltage regulation, output stability, thermal performance, and conversion efficiency. Experimental results showed stable AC operation with load regulation ranging from 2.0% to 3.5%, while the DC output closely agreed with theoretical values and exhibited acceptable ripple levels. Continuous operation over four hours demonstrated reliable performance with only moderate temperature rise. Although efficiency decreased from 59.8% at light load to 46.7% at higher loads due to internal losses, the system maintained satisfactory operation for laboratory experiments and equipment testing. The results demonstrate that the developed power supply is reliable, economical, and suitable for teaching, research, and practical electrical engineering laboratory applications.