SINGLE PHASE INDUCTION MOTOR SPEED CONTROL

BY V/F METHOD THROUGH

MICROCONTROLLER

GUIDED BY: SUBMITTED BY:Shri M.P.S. CHAWLA VIPIN GUPTAAssoc. Professor M.E. (Power Electronics)Electrical Deppt., Sgsits-Indore

Introduction

Speed control was used in DC motor’s because of constant

speed operation at all load and simple controller design

but it was inefficient and required high maintenance.

Now, Due to the advancement in microcontroller and

power electronics; Induction motors are being used in

greater numbers throughout a wide variety of domestic

and commercial applications because it provides many

benefits and reliable device to convert the electrical

energy into mechanical motion.

Continue…….

Because of the only availability of single

phase power for the domestic purpose. So,

here we implemented a single phase motor

speed control hardware to control various

appliances such as washing machines, fans,

hand-held power tools and induction motor-

based centrifugal pump.

Literature Survey literature study is performed about various

methods of controlling the speed of the single

phase induction motor and come to the

conclusion that the best solution is using a PSC

(permanent slip capacitor) motor with three-

phase inverter bridge.

This system allows varying the induction motors

speed, varying the frequency and voltage.

It was made implementing PWM (Pulse Width

Modulation) control algorithms in a PIC

microcontroller.

Microcontroller output signals are sent to the IGBTs

driver and finally to the IGBTs, where DC bus

(generated by a rectifier) is synthesized to provide

two Sinusoidal voltages at 90 degrees out of phase

with varying amplitude and varying frequency to

fed the motor, according to the V/f profile.

Continue…….

Speed Control Of Induction Motor

The speed of an Induction Motor is given as

follows

N = 120 f / P

The torque equation of the induction motor

can be expressed as follows

T = [(k2f2)/(R′r/s)2+(ωL′lr)2 ]*R′r/Sω

Various Speed Control Techniques

Pole changing

Stator voltage control

Rotor resistance control

Stator frequency control

V/F constant control

V/F Method Of Speed Control

In this mode of operation, the voltage across the

magnetizing inductance in the ’exact’ equivalent circuit

reduces in amplitude with reduction in frequency

Smooth variation of voltage and frequency of the AC

output

The current through the inductance and the flux in the

machine remains constant

Torque-speed Curves With V/F Held Constant

SPIM Requirements

Voltage ratio Vaux/Vmain is approximately equal

to the effective turns ratio a, Naux/Nmain(»1.37

for the motor used for this project)

Current ratio is Iaux/Imain=1/a Vaux leads Vmain

by 90º at rated frequency

Constant V/Hz (voltage frequency ratio) for

adjustable speed control

Configuration Of SPIM Drive

Circuit Topology Of Drive

RECTIFIER

INVERTER

MICROCONTROLLER CONTROL CIRCUIT INPUT

Pulse Width Modulation To digitalize the power

To produce the desired RMS output

Triangle wave is used as carrier and reference signal is

sinusoidal wave, whose frequency is the desired

frequency

To produce the desired fundamental component of

frequency

PWM AND FREQUENCY SPECTRUM

Problem Formulation

Input section is replaced with a standard diode

bridge rectifier

Output section has a 3-phase inverter bridge

One end of the main winding and start windings

are connected to one half bridge each, The other

are tied together and connected to the third half

bridge

Circuit Diagram

PIC16F72 Microcontroller To control 3-phase inverter bridge

Generate PWM frequency approximately 8 KHz

Timer1 (1:4 prescale) is counted up from 00 to 634

Gives a dead time of one micro second when the

microcontroller is running at 20 MHz

PORT C <0:5> are initialized to output PWMs

Continue……… A/D channels are initialized to read frequency reference (AN1)

-Frequency reference is read using a potentiometer connected to

A/D channel 1.

Timer0 is used for setting the motor frequency based on the

potentiometer setting

The sine table is loaded into RAM

Timer0 overflow, Timer1 overflow and INT interrupts are enabled

PIC16F72 Pin Description

Microcontroller Limitation Generating software PWM takes significant processing

power. This limits any other application that may be

required to run on the same MCU

The safe PWM frequency range is from 6 khz to 10 kHz

with an operating frequency of 20 Mhz. The PWM cycle

may have an error up to ±5%.

The resolution is also limited between 6 to 8 bits. In

addition to this, generating PWM outputs in firmware uses

the on-chip Timer, program and data memory.

Driver IRAMS10UP60A Integrated Gate Drivers and Bootstrap Diodes

Temperature Monitor

Temperature and Over current shut down

Fully Isolated Package

Low VCE (on) Non Punch Through IGBT Technology

Under-voltage lockout for channels

Continue……..Matched propagation delay for all channels

Low side IGBT emitter pins for current control

Schmitt-triggered input logic

Cross-conduction prevention logic

Lower di/dt gate driver for better noise immunity

Internal Electrical Sechmatic-IRAMS10UP60A

Printed Circuit Board Designing

Eagle PCB layout editor 6.1.0 is used

Developed the schematic of the circuit

Convert it’s schematic into board which is required PCB layout

Schematic of Circuit

PCB Layout

Power Supply5 V DC supply for microcontroller

15 V DC supply for Driver Power Module- IRAMS10UP60A

30 V Isolated power Supply for generate the results

CodingCoding is done in Assembly

language

MP Lab assembler is used for the simulation

MP Lab assembler is also used for generating of Hex file of the code

Results

Auxiliary and Main winding voltage respectively at 25 Hz

Auxiliary and Main winding voltage respectively at 40 Hz

Auxiliary and Main winding voltage respectively at 60 Hz

Implemented Hardware

Discussion & Conclusion It is the single-phase induction motor

that makes the less noise.

Excellent for applications with high on/off cycle rates.

Most reliable of the single-phase motors.

The best choice for variable speed control.

Scope & Future Work In addition, a 3-phase induction motor can

be controlled using the firmware

Gives flexibility to the system without changing hardware

We can protect the hardware by adding over current, over voltage and over temperature peripheral circuitry and complex software programming.