Ejemplo Uso Pic

SERBIAN JOURNAL OF ELECTRICAL ENGINEERING
Vol. 7, No. 2, November 2010, 195-204
UDK: 004.466

Microcontroller Based PWM Controlled
Four Switch Three Phase Inverter Fed
Induction Motor Drive
Nalin Kant Mohanty1, Ranganath Muthu2
Abstract: This paper presents PIC microcontroller based PWM inverter
controlled four switch three phase inverter (FSTPI) fed Induction Motor drive.
The advantageof this inverter that uses of 4 switches instead of conventional 6
switches is lesser switching losses, lower electromagnetic interference (EMI),
less complexity of control algorithms and reduced interface circuits. Simulation
and experimental work are carried out and results presented to demonstrate the
feasibility of the proposed approach. Simulation is carried out using MATLAB
SIMULINKand in the experimental work a prototype model is built to verify the
simulation results. PIC microcontroller (PIC 16F877A) is used to generate the
PWM pulses for FSTPI to drive the 0.5 hp 3-phase Induction Motor.
Keywords: Four Switch Three Phase Inverter (FSTPI), Induction Motor (IM),
Pulse Width Modulation (PWM), Total Harmonic Distortion (THD), Peripheral
Interface Controller (PIC).

1Introduction

Induction motors are being used for many industrial and commercial
applications because it its easy build, high robustness, and generally satisfactory
efficiency. AC induction motors, which contain a cage, are very popular in
variable-speed drives. They are simple, rugged, inexpensive and available at all
power ratings. Progress in the field of power electronics andmicroelectronics
enable the application of induction motors for high-performance drives. The
speed of the induction motor can be controlled by varying its input AC voltage
and frequency using an Inverter.
A standard six - switch three phase voltage source inverter has six switches
in three legs with a pair of complementary power switches per phase. A reduced
switch count voltage source inverter i.e.four switch three-phase inverter
1

Department of Electrical and Electronics Engineering, Anna University, Chennai 600025, India;
E-mail: nkmohanty2003@yahoo.co.in
2
Electrical and Electronics Engineering Department at SSN College of Engineering, Chennai 600025, India;
E-mail: ranganathm@ssn.edu.in

195

N.K. Mohanty, R. Muthu

(FSTPI)] uses only two legs, with four switches. Theadvantage of this inverter
due to the use of 4 switches instead of conventional 6 switches is lesser
switching losses, lower electromagnetic interference (EMI), less complexity of
control algorithms and reduced interface circuits. Several articles report on
FSTPI structure [1-5].
In recent years, with the increasing use of microcontrollers in power
electronics, it becomes possible to use it togenerate the pulse width modulation
(PWM) signals to control the speed of the induction motor. The microcontroller
provides the variable frequency signal that controls the applied voltage on the
gate drive, which provides the required PWM frequency at the output of the
power inverter. Low cost PIC16F877A microcontroller has been chosen for
implementation for ease in development and fastresponse. In addition,
PIC16F877A has high-performance RISC CPU with only 35 single-word
instructions, all single-cycle instructions except for program branches, which
are two-cycles, and operating speed of 20 MHz.

2

Proposed Topology

In the simulation and experimental work, the single phase half bridge
rectifier converts AC power to DC. The DC power is fed to FSTPI. The FSTPI
converts theDC power to controlled 3-phase AC power. The 3-phase induction
motor is driven by the FSTPI. PIC microcontroller 16f877A is used to generate
the controlled PWM pulse for FSTPI. The controlled PWM pulses of
microcontroller are fed to the gate of MOSFETs of FSTPI through the driver
circuit to drive the IM.
2.1 Principle of FSTPI operation
The power circuit of the FSTPI fed IM drive is shown...