PPU design for low power and low cost AC drive

Abstract

Of all the electrical motors, Induction motors are the most widely used because of their reliability, robustness and low cost. However, induction motors do not have their own capability of variable speed operation and due to this reason dc motors were used earlier in most of the electrical drives. In the recent developments of speed control methods have led to the large scale use of induction motor in almost all electrical drives. There are several methods used for speed control of an induction motor such as frequency variation, variable rotor resistance, pole changing, constant V/f control, variable stator voltage, slip recovery method etc., the most widely used method is the constant V/f speed control. In this method, the constant V/f ratio is maintained which in turn provides the steady magnetizing flux so that the maximum torque remains unchanged. Thus, the motor is fully utilized in this method. This dissertation describes the designing and development of motor control card for low power up to 2kW 3-phase motor featuring the IGBT intelligent power module. The developed motor control board is an AC-DC inverter that produces a 3-phase waveform for driving the 3-phase motors either an induction motors or permanent magnet synchronous motors (PMSM) up to maximal 2000 W with or without sensors. The main device presented in this motor control board is a universal, fully evaluated and populated design consisting of a 3-phase inverter bridge based on the 600 V IGBT power module mounted on a heat sink. The power module integrates the power IGBT switches with high voltage gate drivers together with the freewheeling diodes. The board also features the STM32F103 microcontroller which comes with the set of peripherals that makes them suitable for performing both with PM and AC induction motor scalar control. With this the motor control board the system has been designed to achieve power inversion in a compact and reliable way. Such integration saves the PCB space occupation and assembly costs, together with high reliability due to the design simplicity that will lead to the low power and low cost AC drive. The designed board is used for the applications in industrial drives, power tools, high power industry pumps, power fans for HVAC application.