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training manual
Citation preview
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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