The three-phase six-switches voltage source inverter is usually used for industrial motor control and renewable energy systems. However, in order to decrease to size and cost of the drive systems, the three-phase four-switch voltage source inverter has been applied to low-cost motor control and renewable energy system. The fundamental concepts and principles of the three-phase four-switch voltage source inverter are discussed. The mathematical model and space vector modulation of the three-phase four-switch voltage source inverter are proposed. The work is demonstrated by simulation results.