Test And VVVF Application Of Full Digital Three Phase SPWM Singal Generation Chip

A full digital SPWM signal generation chip is designed for electric power .The chip is completed during the period stage of the project. This paper is main concern of the test and the application of the chip in VVVF.The programmable chip can sent out ordered SPWM signal after the control information is written into it by MCU .The clock signal is provide by an oscillating crystal. 40 lead plastic dual-in-line package is selected for the chip. All the function of the chip is tested firstly in the paper. AT89S8252 is selected as the MCU, the output waveform is captured by Phosphor Oscilloscopes: TEKTRONIX TDS3034B and Logic Analyzer: TEKTRONIX TLA601.The test program is written in assemble language. The work voltage range of the chip is 3.3V~5V.The results of test show the function is correct and the chip reaches up to design specification.SPWM signal can invert DC power supply into pulse power supply. The voltage and frequency of AC power supply can be controlled by adjusting the width and period of SPWM pulse, so the SPWM is used widely in power electric. The hardware and software of a VVVF (Variable Voltage variable Frequency) system based on the chip are designed in the paper. The system includes display, keyboard, EEPROM, A/D, UART, safeguard, SPWM signal and so on. The V/F control method is adopted in the system. The software is written in C language and debugged inμVision2. Because the SPWM signal generation in one chip, the characters of the system is control precise 16 bits, MCU efficient, low cost. An experiment was made upon a 1.1KW induction motor. The voltage and current of the motor were captured by the Phosphor Oscilloscopes. The results of experimentation show the width of pulse increase gradually and the current is sine curve, so the motor run steadily. The motor rotate speeds at different SPWM frequency were measured. It can be seen that rotate speed is linear with SPWM frequency. So the motor rotate speed can be controlled by adjusting SPWM frequency.It can be seen that the performance of chip reaches up the application specification, and the design of the VVVF system is successful.