Design And Construction Of A DC-Operated Electric Cooker

CHAPTER ONE

1.0                                                        INTRODUCTION

The work relates to an inverter circuit driving device of an cooker, and more particularly to an inverter circuit of a cooker which is capable of varying the width of a drive pulse to an inverter with a variation in an input voltage so as to vary a switching frequency of the inverter, thereby stabilizing heating power generated by a switching operation of the inverter and preventing an internal device of the inverter from being damaged due to the variation in the input voltage.

The inverter circuit is applied to the cooker to heat an object (load) to be cooked by controlling a power switching device therein. The power switching device performs a switching operation in response to a control signal to apply a drive voltage to the induction coil for the inner pan so as to heat the inner pan. The inverter circuit comprises a power source for supplying a commercial alternating current (AC) voltage, a rectifier for rectifying the AC voltage supplied by the power source, a filter for filtering an output voltage from the rectifier and an inverter for performing a switching operation based on an output voltage from the filter to apply a drive voltage to the coil for the inner pan.

The inverter circuit further comprises a trigger circuit for varying the operation or state of a specific circuit at a rising or falling edge of a pulse. The trigger circuit generates a drive pulse to drive a switch of the inverter. The switch is turned on when the drive pulse goes “high” in level, and off when the drive pulse goes “low” in level. Here, a voltage applied across the switch is referred to as a “switched voltage”.

The inverter circuit further comprises a switch driver for transferring the drive pulse from the trigger circuit to the inverter to drive the switch of the inverter.

The switch of the inverter is adapted to perform the switching operation in response to the drive pulse transferred from the switch driver to generate heating power, which is used as a heating source for cooking a load to be heated (an object to be cooked). A withstand voltage of the switch against the switched voltage is limited in its range according to specifications of the switch. In general terms, the higher the withstand voltage, the higher the cost of the switch, resulting in an increase in production cost.

1.1                                                   AIM OF THE PROJECT

The main aim of this work is to design a circuit that will operate or power a heater using battery or dc source.

1.2                                             OBJECTIVE OF THE PROJECT

The objective of the work is to design and construct a battery operated electric cooker which is powered by rechargeable battery when there is power outage. In this work, a 12v rechargeable battery is used to power the whole system.

1.3                                         SIGNIFICANCE OF THE PROJECT

After knowing in detail what a dc operated cooker is and how different useful it is to make appliances work at residential and industrial levels students should also know the advantages.

• Also use of rechargeable battery energy helps in saving money many people.
• This device helps people who use limited amount of electricity.
• A dc operated cooker is more environmentally friendly.
• Also their maintenance does not cost much money.

1.4                                           LIMITATION OF THE PROJECT

• Initially you need to shell out a lot of money for buying a battery.
• It will work effectively and produce direct current only when the battery is fully charge.

1.5                                              PURPOSE OF THE PROJECT

The purpose of this circuit is for laboratories and shops for carrying out small scale cooking jobs such as melting ornaments, or boiling small quantity of liquids using battery

1.6                                                 SCOPE OF THE PROJECT

This device compose of an inverter circuit cooker which is capable of controlling a switching frequency of an inverter in a variable manner according to a variation in an AC voltage to the inverter circuit and performing a switching operation of the inverter at the controlled switching frequency, in order to prevent a switch determining the supply of a drive voltage for the heating cooker from being damaged as well as to heating the cooker, so that a margin of a switched voltage across the switch is increased to enhance durability of a product, no high-cost switch is required to curtail a production cost, and power of the inverter does not vary greatly with variations in a load to be heated and in the AC voltage, thereby enhancing stability and reliability of the inverter circuit.

1.7                                        PROJECT WORK ORGANIZATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this work is on the introduction to an automatic voltage stabilizer. In this chapter, the background, significance, objective limitation and problem of the study were discussed.

Chapter two is on literature review of the study. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.

CHAPTER FIVE

5.1                                                           CONCLUSION

At the end of this work, a dc operated electric cooker was designed. The circuit provide an inverter circuit which is capable of controlling a switching frequency of an inverter in a variable manner according to a variation in an AC voltage to the inverter circuit and performing a switching operation of the inverter at the controlled switching frequency, in order to prevent a switch determining the supply of a drive voltage for the cooker.

This device compose of power supply means for rectifying and filtering a commercial AC voltage to supply an input voltage to the cooker; an inverter for performing a switching operation based on the input voltage from the power supply means to heat the cooker; constant-power reference level generation means for generating a constant-power reference level of the cooker on the basis of a variation in the AC voltage and a variation in a load of the cooker; and inverter driving means for outputting a drive pulse to control a switching frequency of the inverter in a variable manner according to a difference between the constant-power reference level and a level of the AC voltage so as to maintain power of the inverter at a constant level.