A study on efficiency of voltage source and current source converter systems for large motor drives

This paper calculates and compares the efficiency and loss distribution in three most popular state-of-the-art types of large motor drive systems; current source drive with active front-end rectifier, current source drive with 18-pulse thyristor rectifier, and three-level voltage source drive with 12-pulse/274-pulse diode rectifier. For converter systems with efficiencies better than 90%, it is suggested to calculate or measure the losses of all the components in separate, and add up to calculate the total efficiency. Simple and accurate method of calculating switching losses for current source and voltage source converter is proposed. Through the calculation and measurement of each loss factor such as switching losses, conduction losses, snubber and filter losses, three-level voltage source drive system has been found to have the highest efficiency of 98.77% under the rated load of 106MW.