S/M No. :

Jun . 2002

DAEWOO ELECTRONICS CO., LTD.http : //svc.dwe.co.kr

PRODUCT : Microwave Oven

Training Manual

MODEL : ALL model

1. PRINCIPLES ......................................................................................1

2. CLASSIFICATION ..............................................................................6

3. CONTAINERS .....................................................................................8

4. BASIC STRUCTURE ..........................................................................9

5. BASIC CIRCUIT AND FUNCTIONS ................................................10

6. HOW TO CHECK MAJOR COMPONENTS.....................................17

7. MAJOR TROUBLE SHOOTING .......................................................19

8. CAUTIONS ON USING THE MICROWAVE OVEN..........................23

9. NEW MODELS WITH SPECIAL FUNCTION...................................24

Contents

1

1. PRINCIPLES

1-1 Origin of Concept of the Microwave Oven

A major characteristic of mankind that animals do not have is the use of "fire". Since the World War II,

mankind has gained access to various kinds of new fires, the most outstanding of which is the nuclear

technology. The microwave heating technology, being used for the microwave oven, is also one of the

new fires.

The microwave oven has first been introduced to the market in 1945, by RAYTHEON Company of U.S.A.

in the name of RADAR RANGE. The idea is said to have been inspired by the chocolate molten in the

pocket of an engineer by the influence of the microwave from a RADAR.

The traditional heating method like burning of firewood, charcoal and petroleum of heating by electric

heater depends on surface heating in which the surface of the objects being heated gets heat through

flame of heat wave(infrared ray), and the inner contents of the objects gradually through thermal

conduction inside the material.

On the contrary, the microwave heating technology is the internal heating technology, in which

microwave(a kind of electromagnetic wave) penetrates and is absorbed into the objects being heated(like

food), thereby heating them from inside.

The microwave heating technology has the following advantages compared with the traditional heating

technology :

1 short time to heat

2 high thermal efficiency because only the objects being heated are heated

3 almost nonexistent heating of the heating equipment itself

4 better safety to users due to the reason described in 3

The microwave heating technology, with the above advantages, being a clean and energy saving

technology, is used widely for medicinal purposes as well as industrial purposes including food treatment,

various drying processes, molding and sterilization processes.

2

use ofelectromagnetic

wave

0.00.20.40.60.81.0

1-2 Thermal source of the Microwave Oven

The energy source of the microwave oven is the electromagnetic wave. TV(UHF and VHF), radio, stereo

audio equipment, and the high frequency treatment equipment used for treating neuralgia or rheumatism

are all everyday examples of devices using electromagnetic wave.

The electromagnetic wave is changed into the picture by TV, into voice by radio or stereo audio

equipment, and into heat by the microwave oven.

microwave oven• 2,450 MHz• changed into heat

TV• VHF : 30 ~ 300 MHz• UHF : 300 ~ 3000 MHz• changed into picture the and voice

radio• 560 ~ 800 KHz• changed into voice

medicinal equipment• 2,450 MHz• changed into heat

3

dish container

electromagnetic wave

food

(vacuum tube)magnetron

The friction heat is generated

The electromagnetic wave is emitted from the antenna of the magnetron of the microwave oven.

The frequency of this electromagnetic wave is 2,450MHZ, i.e. there is a 2,450,000,000 oscillations

(change of polarity between + and -) per second. The electromagnetic wave vibrates the water molecules

contained inside the food, which generates friction heat. This friction heat propagates all over the food

and cooks it. The electromagnetic wave energy thus changes into high efficiency thermal energy.

If wood is rubbed against wood. If hand is rubbed against hand. If water molecules in the food is

rubbed against other water

moecules while rotating

4

1-3 Characteristic of Electromagnetic Wave

The ability to heat only the food without heating the container comes from the ingenious use of the

characteristic of the electromagnetic wave.

- Electromagnetic wave is absorbed by water.

Electromagnetic wave always travels straight. However, if

electromagnetic wave meets materials containing water, it is

absorbed by the water and generates heat. Microwave oven uses

this characteristic to heat materials.

- Electromagnetic wave penetrates porcelain of glass.

Electromagnetic wave penetrates materials that do not contain

water like porcelain of glass.

- Electromagnetic wave is reflected when it meets metals.

Electromagnetic wave is reflected when it meets metallic surface.

Thus, if container with metallic surface is used, food inside the

container will not get heated. Using aluminum foils to wrap the tail

of a fish when cooking is the example of using this characteristic,

not to burn it due to too much heating.

absorption

penetration

reflection

5

Also, traditional cooking methods like "boil water in the pot" or "fry eggs in the frying pan" depend on the

principle of thermal conduction. That is, heat from gas fire, charcoal fire or electric heater is first conveyed

to the pot or frying pan and then conveyed to food.

However, microwave oven generates friction heat inside food and heats only the food itself. Since heat is

generated from inside, time to heat is much reduced compared with traditional heating method. That is

also why heat loss is reduced.

Only food, inside and outside, is heated at the

same time.

Heat is transmitted to pot first, then to water,

and then to food.

microwave oven pot or frying fan

6

2. CLASSIFICATION

Microwave ovens can be classified into household use / professional use by use, single function / multiple

function by function, mechanical / electronic by control mechanism, and turn table type / stirrer fan type by

method of electromagnetic wave distribution. They can also be classified by capacity or by existence of

output switching.

2-1 Classification by function

microwave oven + toaster

microwave oven + oven

microwave oven + oven + grill

microwave oven + oven + grill + toaster

microwave oven + oven + grill + steam cooker

microwave oven + oven + grill + home bakery

multiple functions microwave oven

microwave oven

single function microwave oven

7

2-2 Classification by Control Mechanism

2-3 Classification by Method of Electromagnetic wave distribution

After the timer knob and output level adjusting

knob are set to desired value, the microwave

oven operates until the timer motor reaches the

set time, with the set output level.

Operation is made by using touch buttons on

the control panel. Users can program their own

inputs by themselves, thus operation is various.

Food dish is rotated so that every part of food

receives electromagnetic wave and is well

cooked.

Stirrer fan installed in the ceiling of cavity

rotates to distribute electromagnetic wave

emission.

Mechanical Electronic

Turn table type Stirrer fan type

8

3. CONTAINERS

- thermo-resistant glass(pyroceramic of pyrex)

- thermo-resistant ceramic,porcelain

- china pot or gratin dish

- normal ceramic ofporcelain

- normal glass

- thermo-resistant plastic(PP)

- metals like aluminum andfoil, gridiron or metalskewer

- wood, bamboo or paper

- aluminum foil

- wrap

materials of containers for microwave oven cooking for heater cooking

- can be used but may be broken.If cooled down abrubtly,

- can be used.

- can be used but those with goldplating, silver plating or silver foilcan cause sparks and must notbe used.

- can be used but those with bigdifference in thickness along itsshape can be broken easily andmust not be used. (likereinforced glass or cup glass)

- can be used but should be ableto endure 120 degree celsius.

- cannot be used since theycauses sparks.

- cannot be used since they willbe scorched or burned.

- cannot be used normally butcan be used to reduce the effectof electromagnetic wave, likewrapping the tails of fish.

- can be used but must not beused to wrap food like meat or afry that requires hightemperature to cook.

- can be used but may be broken.If cooled down abrubtly,

- can be used.

- can be used.

- cannot be used.

- cannot be used.

- can be used but those withwooden or plastic handles cannotbe used.

- cannot be used since they willbe scorched or burned.

- can be used.

- cannot be used since they willbe melt.

* Containers that cannot be used :

normal plastic containers (styrols, pp, melamin, penolic, urease or lacquer ware)

9

4. BASIC STRUCTURE

assembly

1

cabinet

2

control

panel

3

door

4

chassis

5

bottom

plate

6

harness

wiring

10

5. BASIC CIRCUIT AND FUNCTIONS

5-1 Basic circuitry (example)

5-2 Power Supply Circuit

The power supply circuit is provided to supply power to the microwave oven and consists of the power

cord with plug and the line noise filter for EMI protection. Especially, the power cord with plug should be

of three prongtype (live/neutral/ground). The ground wire of the cord should be well grounded to the

microwave oven chassis and the ground prong of the plug should be well grounded to the ground pole of

the socket outlet.

5-3 Interlock Monitor System

The interlock monitor system is a device to prevent electromagnetic wave emission generated by the

magnetron from leaking outside the cavity, even when the door is opened while the primary interlock

switch is out of order. That is, if the primary interlock switch is out of order and its contacts are closed, the

interlock monitor switch will operate to form a closed loop, thus blowing out the main fuse. This cuts off

the power input to the microwave oven, stopping the oscillating operation of the magnetron. This switch is

an important safety device.

11

5-4 Control Circuit

This circuit is provided for adjusting cooking time and output level ; in case of mechanical type, by rotatingthe knob, the cooking time and output level are adjusted. For example, suppose that the desired outputlevel is level 5 and maximum output is 850W. The oscillation time and output are as follows.

In case of electronic type, a microprocessor is provided for control, so adjustment is more various.

Output adjustment switch (V.P.C : variable power controller) is switched on and off with a cycle time of30 sec.

when door is open, normal when primary switch is out of order

Variable power setting ON/OFF time, sec. Power %

(HIGH) 30.0 / 0 850 W 100%

(MED HIGH) 23.2 / 6.8 657 W 77.3%

(MEDIUM) 16.5 / 13.5 468 W 55.0%

(DEFROST) 9.8 / 20.2 278 W 32.7%

(WARM) 5.0 / 25.0 142 W 16.7%

Power level "ON/OFF time, sec Power (W) %1 3/26 88 10.3%

2 5/24 147 17.2%

3 8/21 234 27.6%

4 11/18 322 37.9%

5 14/15 410 48.3%

6 17/12 498 58.6%

7 20/9 586 69.0%

8 23/6 674 79.3%

9 26/3 762 89.7%

10 29/0 850 100%

12

5-5 Overheating Protection Device

Overheating protecton device is the safety device consisting of a magnetron thermostat or a cavity

thermostat. It cuts off the power when the magnetron or the cavity is overheated, and switches power ON

again when temperature goes down. The ON/OFF temperature of the thermostats are different between

each model.

5-6 High Voltage Generator

The magnetron needs an oscillation power (DC 4000V) and a filament power (AC 3.4V). The high

voltage generator consists of a high voltage transformer, a high voltage capacitor, and a high voltage

diode. AC 2000V voltage generated at the secondary winding of the high voltage transformer is boosted

to halfwave DC 4000V by the high voltage capacitor and the high voltage diode and then supplied to the

magnetron.

The following are a circuit diagram and an exploded view of the high voltage generator.

When repair is needed, it should be done after

disconnecting power plug from the socket outlet and

discharging the high voltage capacitor. To discharge

it, shortcircuit the two parts indicated by the arrow.

OR FA F

H.V. CAPACITOR

H.V. DIODE

H.V.FUSE

MAGNETRON

WIRING COLOROR: ORANGE

H.V. TRANSFORMER

circuit diagram exploded view

SHORT

13

5-7 Microwave Generator

Microwave generator is a magnetron : it receives power from the high voltage generator and generates

2,450 MHZ microwave.

Care should be taken to the following when it should be replaced.

Metallic gasket plate should not be lost.

5-8 How to measure microwave output power (IEC 705 clause 12)

P = 4,187Mw(T2 - T1) + 0.55Mc(T2-T0) / t

Mw : Mass of the Water (1000g ± 5g) To : Ambient Temp. (20˚C ± 2˚C)

Mc : Mass of the Container T1 : Initial Temp. of Water (10˚C ± 1˚C)

t : Heating time (sec.) T2 : Final Temp. of Water

Heating time(t) of microwave oven can be approximately calculated by following.

t = 4,187 x 10 / 900 = 47

Here 1) T2 = 20, T1 = 10 and T0 = 20

2) Power output is 900W

3) The filament heat-up time for magnetron is excluded

* Power output vs Heating time

Power output (P)

Heating time (t)

600

70

650

64

700

60

750

56

800

52

850

49

900

47

950

44

1000

42

1050

40

1100

38

14

5-9 Leakage (Radiation) test (IEC 335-2-25 Clause 32)

1) Conditions

1 Load : 275 ± 15g (20 ± 2˚C)

2 Beaker : 600cc (85mm Diameter)

3 Location : The center of tray

4 The limit of leakage : 5mW/cm2 (4mW/cm2 : DAEWOO)

5-10 Installation

1) Steady, flat location

This microwave oven should be set on a steady, flat surface.

2) Leave space behind and side

All air vents should be kept a clearance. If all vents are covered during operation, the oven may

overheat and, eventually, cause oven failure.

3) Away from Radio and TV sets

Poor television reception and radio interference may result if the oven is located close to a TV, Radio,

or Antenna, feeder and so on.

4) Away from heating appliances and water taps

Keep the oven away from hot air, steam or splash when choosing a place to position it, or the

insulation might be adversely affected and breakdowns occur.

5) The minimum height of free space necessary above the top surface of the oven shall be maintained

according to user manual.

5-11 Efficiency

E = OUTPUT / INPUT x 100%

15

5-12 The Principles of Oscillating Magnetron

The primary of high voltage transformer is 230V.

for example

N1 = 230 turns

N2 = 2200 turns

by formula

V2 / V1 = N2 / N1 = I1 /I2 V2 = V1 x N2 / N1 = 230 x 2200/ 230 2200V

The secondary of high voltage is approx. 2200V.

High voltage capacitor has the function which store the electric charge and high voltage diode has the

function which rectify the current.

By these functions, AC 2200V is changed into approx DC 4.1KV.

DC 4.1KV is applied to the anode of magnetron. 3 volts is generated from the filament winding of the high

voltage transformer.

by formula

N1 = 230 turns

N2 = 3 turns

by formula

V2 / V1 = N2 / N1 V2 = V1 x N2 / N1 = 230 x 3/ 230 3V

This filament voltage is applied to the magnetron to heat the magnetron filament

16

5-13 The explanation for major components are as follows.

• Fan motor : This component has the function which cools the magnetron and transformer. If fan motor is

out of order, temperature is rising so abrupt that the magnetron thermostat or H.V. Fuse will be cut off.

In case of not having the magnetron thermostat, the stuffs (coupler, roller guide) inside the cavity may

be melted.

• Geared motor : This component has the function which distributes the microwave uniformly and has the

foods cooked well.

• Cavity lamp : This component has the function which lights the inside cavity

• Noise filter : This component has the function which filters conductive noise flowing from line to line.

• Oven thermostat (Cavity thermostat) : This is the device which protects the appliance during the

abnormal operation

• Fuse : This is the component which protects the set on breaking out overcurrent, the break down of

insulation, short, ets.

• H.V.Fuse : This is the component which protects overcurrent from H.V. Transformer to H.V. Capacitor.

• Timer : This is the component which controls the time and output power.

• Transformer H.V. : This is the component which transforms 230V general input into 2000V.

i.e. the transformer has pass core for leakage flux to obtain the stable power source.

17

6. HOW TO CHECK MAJOR COMPONENTS

Components should be checked only after removing the power plug from the socket outlet, discharging

the high voltage capacitor and disconnecting power lead wires from the components.

magnetron both ends of the filament normal : less than 1Ω

filament housing normal : ∞

high voltage transformer primary winding normal : 0 Ω

secondary winding normal : about 100 Ω

primary winding and core normal : ∞

filament and core normal : ∞

high voltage capacitor pin to pin normal :

ammeter should show

some resistance value for

a moment but then

should go to ∞

abnormal :

∞ or 0Ω always

pin to case normal : ∞

abnormal : 0Ω

components points to be checked result

R X 1

R X 1000

R X 1

R X 1

R X 1

R X 1000

R X 1000

R X 1000

18

thermostat normal : 0Ω

abnormal : ∞

fan motor normal : ∞

abnormal : 0Ω

high voltage diode forward direction normal : continuity

abnormal : 0Ω

reverse direction normal : ∞

abnormal : continuity

fuse (including high normal : 0Ω

voltage fuse) abnormal : ∞

safety switch NC. NO Type switch off switch

(door open) (door close)

NO. Type

NC. Type

light bulb (lamp) normal : ∞

abnormal : 0Ω

components points to be checked result

R X 1

R X 1

R X 1000

R X 1000

R X 1

COM

NCNO

COM

(CHECK)COM-NO

NO

(CHECK)COM-NC

COM

NC

R X 1

NC NO

RX1 RX1

RX1 RX1

19

7. MAJOR TROUBLE SHOOTING

Symptom

1) After the oven isstarted, the lampdoes not light andfan motor doesnot operate

check if fuse blown. if blown

if OK

replace fuse

check lamp filament if cut it off replace lamp

check if power plugis properlyconnected to socketoutlet

if not connected make connection

check lamp wiring if improper wired repair wiring

points to check result required actions

check fan motorwiring

if improper wired repair wiring

check fan motor if abnormal

if OK

if OK

check safety switch if abnormal replace safetyswitch or adjustdoor positioningif OK

check relay

in case of electronictype

if abnormal replace relay

replace PCBassembly

if OK

replace fan motor

if OK

20

Symptom

2) Operation isnormal but foodis not heated

check wiring of highvoltage transformerand magnetron.

if improper

if OK

repair wiring

check high voltagefuse

if fuse blown replace fuse

points to check result required actions

if OK

check high voltagecapacitor

if abnormal replace capacitor

if OK

check high voltagediode

if abnormal repair diode

if OK

check resistance ofhigh voltagetransformer

if abonormal replace transformer

if OK

Check power inputto main relay(DC 12V or 24V)

if improper replace main relaydriver transistor

if OK replace PCBassembly

In case of electronictype, check mainrelay.

if abonormal replace main relay

if OK

check magnetron if abnormal replace magnetron

21

Or in case that startbutton is pressedbut the oven doesnot operate.

Symptom

3) Incase ofelectronic type,power plug isinserted but thedisplay is notlighted:

check input power if OK

points to check result required actions

check if power plugis properlyconnected to socketoutlet

if abnormal replace socketoutlet

check fuse if fuse blown

if OK

replace fuse

check secondaryvoltage of lowvoltage transformer

if fuse abnormal

if OK

repair transformer

check safety ofinterlock system

if fuse is againblown

if abnormal

if OK

adjust doorpositioning orreplace safetyswitch

check for shortcircuit in internalwiring orcomponents

if short circuit found correct theproblem

replace PCBassembly

22

Symptom

4) In case ofelectronic type,function keys arepressed but themicrowave ovendoes not operate

check contacts ofmembrane switch

if abnormal

if OK

replace membraneswitch

points to check result required actions

check connectorbetween membraneswitch and PCB

if abnormal repair connection

replace PCBassembly

if OK

check door-openlimit switch

if abnormal adjust doorpositioning

repalace door-openlimit switch

if OK

check if there arefood residue onspatter shield

if abnormal clean or replacespatter shield

if OK

check if container ismetallic

use propercontainer

5) There are sparksin cavity

23

8. CAUTIONS ON USING THE MICROWAVE OVEN

1) BE CAREFUL ON INSTALLATION

• It should be earthed.

To protect electric shock, the earth should be installed.

• Electric capacity

Use a plug receptacle more than 15A.

Don't use other appliance at the receptacle at the same time.

If use like that, house breaker will be cut off.

2) FOR SAFE USE

• The prohibition of use except the purpose of cooking.

Don't use the tree, paper, bar, handkerchief, etc, in the dry.

If you heat these stuffs, it causes fume, ignition and fire.

Don't cook the eggs in the shell and bottle with not opening.

3) THE RIGHT METHOD TO CLEAN THE SET

• THE DOOR - should be cleaned with a damp cloth do not use aerosol cleaners, caustic cleaners or

abrasive powder cleaning agents as this may scrach the surface and impair vision into the oven.

• THE OUTER CASING - is cleaned with mild soap and damp cloth.

Do not use any type of abrasive cleaner.

• THE DOOR SEAL AREA - must also be kept particulary cleaning to ensure a tight seal to keep in

microwave.

•THE GLASS TURNTABLE - can be easily removed for cleaning at the sink. Wipe up spillovers with a

paper towel or cloth before removal of the turntable.

• INTERIOR SURFACE - is cleaned with soft cloth and warm water.

Do not use any abrasive cleaner. For heavier soil, use baking soda or a mild soap : rinse throughly

with hot water.

24

9. NEW MODELS WITH SPECIAL FUNCTION

9.1 Microwave Oven with Ultraviolet Lamp, Models KOR-633V and KOR-637V

1) UV light

Description - Ultraviolet processing involves the use of radiation from the ultraviolet region of the

electromagnetic spectrum for purposes of disinfection. Typically, the wavelength for UV processing

ranges from 100 to 400nm.

UVA: 315 to 400 nm - changing in human skin and lead to tanning

UVB: 280 to 315 nm - causing skin burning and eventually lead to skin cancer

UVC: 200 to 280 nm - inactivating bacteria and virus and lead to kill them, germicidal range

Property - Germicidal properties of UV radiation are mainly due to DNA mutations induced through

absorption of UV light by DNA molecules. It is primarily useful for sterilization and/or sanitation of air ,

the surfaces of various material and water or liquid. UV light can not transmit glass, steel, plastic, and

vinyl, etc, and so shall be irradiated directly onto the object to sanitize well.

2) Application

Germicidal lamp( UV Lamp ) efficiently emits a large amount of ultraviolet rays 253.7nm which have

excellent germicidal effect. This lamp has structures and electrical characteristics similar to those of

general fluorescent lamps used for illumination but use ultraviolet ray glass which efficiently transmits

ultraviolet ray at 253.7nm.

The models KOR-633V and KOR-637V have two separate function such as microwave cooking and uv

sanitizing, however separately operate by different key button on control panel.

The UV system consists of electrical components such as UV lamp, Ballast, and Glow starter and

mechanical parts such as lamp cover and socket.

The UV lamp rated 4W and Glow starter are equipped on top side of the oven cavity and irradiate the

UV light through multi-pierced holes. The Ballast is

equipped on base plate.

GS

1 GL

Germicidal Lamp

Ballast

Glow Starter

AC POWER INPUT

2

Circuit diagram

25

9.2 Convection Oven with 3 Dimensional Power Heating System, Models KOC-1B0K and

KOC-910K

1) Construction

3 powerful heaters are equipped on three sides of the oven cavity. These heaters heat up instantly

allowing even distribution inside the oven and cook beautiful results, browned to perfection.

TOP HEATERQUARTZ HEATER

(550W x 2EA)

REAR HEATERQUARTZ HEATER

(550W x 2EA)CONVECTION FAN

BOTTOM HEATERSHEATHED HEATER (400W)

26

2) Function

- Three Grills Cooking

> Browning Grill : The ‘QUARTZ’ grill heats up instantaneously allowing your dishes to be cooked

quicker and tastier.

> Crisp Grill: The bottom grill heats the base of your food directly and makes it crispy at the same

time.

> Double Grill: With the top and bottom grill working simultaneously, grilling is done on ’both sides’ of

the food

- 5 Combinations Cooking

COMBI. 1CONVECTION +

M/W

COMBI. 3CONV. + DOUBLE

GRILL

COMBI. 2CONV. + CRISP GRILL

+ M/W

COMBI. 4BROWNING GRILL +

M/W

COMBI. 5DOUBLE GRILL +

M/W

VISION CREATIVE, INC. 중구 남대문로 5가 526

대우재단빌딩 16층

담담 당당 김김용용준준 대대리리님님 TTEELL

MMOODDEELL micrro wave oven training manual

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