Regenerative Active Electronic Load for Testing Power Transformers Under Linear and Nonlinear Conditions

A significant number of power apparatus, before being commercialized or during maintenance, are submitted to laboratory tests where real operation conditions are emulated. These tests generally demand high energy consumption which increases the maintenance costs and the overall equipment investment. This paper proposes a platform to test power transformers with return of energy (closed loop) to the system, reducing the power consumption to the inherent equipment losses. Besides the low energy consumption, the proposed system permits flexible tests and operation with variable power factor. The transformer under test can be submitted to different load profiles, including harmonics injection, which is not generally addressed in the traditional procedures. The control structure and constructive characteristics of a 75-kVA test bench are presented and the methodology is validated by testing a 50-kVA distribution transformer. The experimental results are discussed, and the overall system efficiency is demonstrated.