Efficiency Evaluation of Three Phase and Single Phase C2C Self-Excited Induction Generator for Micro Hydro Power Application

Squirrel-cage induction motor (SCIM) is used as generator to a great extent for micro hydropower applications due to their robustness, brushless construction, low cost, reliability, rare maintenance, and availability in a wide power range. Squirrel-cage induction generator (SCIG) normally requires excitation capacitors to build up the terminal voltage from residual magnetism. However, for rated and stable voltage and frequency operation, selection of an appropriate size of excitation capacitor is crucial. This paper presents the efficiency evaluation of an SCIG with different excitation capacitors to supply three-phase and single-phase resistive loads. A 1.5-kW three-phase SCIM was selected as the SCIG driven by a 3-kW three-phase SCIM as a prime mover. The shaft speed was controlled by a variable speed drive (Yaskawa A1000) with an incremental encoder for the speed feedback. Shaft torque was obtained from a torque sensor (TRB-2K) installed in between the two machines. Parameters of the SCIG were determined by DC, no-load, and locked rotor tests, then the required excitation capacitance was calculated. For three-phase operation star connected SCIG was excited by the capacitors in star connection to supply a three-phase resistive load. For the single-phase operation, the delta connected SCIG was excited with so-called C2C configuration.