ac dynamometer includes qc100 series horizontal high-speed ac electric dynamometer with two stage ac motor, qc200 series horizontal low-speed & big-torque ac electric dynamometer, and qc300 series vertical ac electric dynamometer. they test the following items: speed characteristic, load characteristic, durability characteristic, mechanical efficiency, speed tuning characteristic testing for general utility small engine (includes speed-tuning testing, abrupt-increasing-load testing, abrupt-decreasing-load testing, and fluctuant rotating speed testing), and curve method testing on duty (optional).