Total loss comparison of inverter circuit topologies with interior permanent magnet synchronous motor drive system

In this paper, the losses of a drive system for electric vehicles (EVs) which consists of the interior permanent magnet synchronous motor (IPMSM) is analyzed. The applied power converter is distinguished into a 2-level inverter and a 3-level inverter, respectively. In addition, two modulations are applied typically in the inverter, known as Pulse width modulation (PWM) at low speed region and 1-pulse modulation (square wave modulation) at middle or high speed regions. This paper discusses the appropriate interchange point between these modulations in order to achieve minimum loss, by analyzing and comparing the losses for each of the inverter. The total loss is divided into the inverter loss and motor loss, where the inverter loss is calculated by the simulation and the motor loss is analyzed by two-dimensional finite element method (2D-FEM). As a result, the total loss which is composed of the 3-level inverter and the motor losses are shown lower than that of the 2-level inverter. The losses of the 3-level inverter decreases by 5.8% compared to that of the 2-level inverter at base speed. In addition, when the carrier frequency is 5 kHz, the loss of the motor drive system achieves the smallest. Furthermore, the losses of the motor drive system are evaluated by the experiment. According to the results, the high efficiency can be achieved by 1´pulse modulation.