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An Engineering Perspective Of…
Microwave LaboratoryArchitectures, Planning and Methodology
For Food Safety
June 21, 2012International Microwave Power InstituteAnnual Symposium Las Vegas NV USA
Steven J. DruckerChief Technology Officer
Microwave Science JV LLCNorcross GA USA
© Microwave Science JV LLC 2012
An Engineering Perspective Of…
• IEC Testing Protocols
• Microwave Oven Selection
• Voltage, Power Factor and IEC Oven Power
• The Multi-Disciplinary Challenge
• Q&A and Equipment Demonstration
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Why a sound IEC oven testing protocol matters:
IEC testing is a several times daily NRTE foods’
Validation best practice
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
July 2008: the GMA
specifies IEC 60705-2006
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
June 2010: The U.S. DOE rejectsIEC 60705-2006 as neither accurate nor
repeatable
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
DOE mixed signals: IEC 60705-2006 best for
ovens but IEC 705-1988 best for food?
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
June 2012. DOE invites comment re the incorporation of the newly revised IEC 60705
protocol into its standards
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Accurate, repeatable and expressive of microwave oven cooking efficiency
(Portions used by permission. © 2012 Robert F. Schiffmann. All rights reserved)
In the continued absence of a U.S. DOE standard, it is proposed that
the ‘best effort’ protocol is IEC 705-1988, modified
An Engineering Perspective Of…
• IEC Testing Protocols
• Microwave Oven Selection
• Voltage, Power Factor and IEC Oven Power
• The Multi-Disciplinary Challenge
• Q&A and Equipment Demonstration
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Could buying your ovens online be your biggest mistake?
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
If a single oven operates at multiple wattages as a
matter of course, could you have just one oven?
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Fact: Identical model/brand microwave ovens vary greatly one to another, and each
to itself daily, in power output
15.3 Mm units microwave oven 2008 imports:
30% < 22.5L (small < 0.8 cubic feet)
15% 22.5-31L (mid sized 0.8 to 1.1 cubic feet)
55% > 31L (large 1.1 to 2.1 cubic feet)
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Countertop microwave ovens 411 circa 2011:
Manufacturer . LG Tianjin
LG Tianjin
MideaLG TianjinSharp (Malaysia)LG Tianjin
GalanzMidea
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Caution:
Don’t buy the same oven twice!
An Engineering Perspective Of…
• IEC Testing Protocols
• Microwave Oven Selection
• Voltage, Power Factor and IEC Oven Power
• The Multi-Disciplinary Challenge
• Q&A and Equipment Demonstration
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Do microwave ovens exhibit chronic unexplainable multiple personality disorder?
—e.g. 1100 watts on the box, 850 IEC watts over morning coffee, 750 IEC watts mid-afternoon and 900
IEC watts on Sunday!
http://www.powerqualityworld.com/2011/04/ansi-c84-1-voltage-ratings-
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Power company voltage varies within bounds set forth by the American National Standards Institute (‘ANSI’) in concert with
NEMA and EEIS
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
What does it mean to food safety and IEC oven power
if your wall voltage ranges from 106VAC to 127VAC—
even before the effects of AC power factor?
Power Factor—AC is not DC—or why you should care
In an ideal DC current world, all power is ‘Real’.
In the real AC current world, however, plug an electrician’s voltmeter into an outlet, and what you measure is something called Apparent Power, often far greater than ‘Real Power’.
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Understanding AC Power Factor debunks
the myth that microwaves differ night and
day absent rhyme or reason
Power Factor—the IEC testing ‘Eminence Grise’“The power factor of an AC electric power system is defined as the ratio of the real power flowing to the load to the apparent power in the circuit, and is a dimensionless number between 0 and 1. “Real power is the capacity of the circuit for performing work in a particular time. Apparent power is the product of the current and voltage of the circuit. “Due to energy stored in the load and returned to the source, or due to a non-linear load that distorts the wave shape of the current drawn from the source, the apparent power will be greater than the real power.”http://en.wikipedia.org/wiki/Power_factor
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Fluorescent lights, pumps, motors and refrigerators greatly
influence power factor…how many of what sizes are near your
laboratory or home kitchen?
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Perfection is not an option
A $3k solution may buy you 75%
A $30k solution then would buy you 76%
There is NO 100% solution to the influence of AC power factor
Power Factor management is an asymptote !
Power (hp) Speed (rpm)Power Factor For AC Motors1/2 load 3/4 load full load
0 - 5 1800 0.72 0.82 0.845 - 20 1800 0.74 0.84 0.8620 - 100 1800 0.79 0.86 0.89100 - 300 1800 0.81 0.88 0.91
Asymptote (rhymes with anecdote, antidote, assault
boat, billy goat, cashmere coat, casting vote, creosote,
dead man's float, entrecôte…)
Best practice for management external to the microwave* of AC power factor and
Mains Voltage variations:
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
DO NOT use a voltmeter—plug-in, clamp on or a Simpson
REPEAT: DO NOT use any kind of electrician’s voltmeter
Use a 2500 KVA digital wattmeterSet the wattmeter to read out in VOLTS
Use a 2500 KVA AC variable transformer (‘Variac’).Before every test, ADJUST the Variac so the WATTMETER
reads 120V (or the desired voltage)
(* But are there NRTE food safety voltage compensation
solutions inside of ovens for use outside the lab?...)
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
STACO ENERGY Variable AC transformer 2500 KVA
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Match Variac and Digital Wattmeter
KVA design capacities
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Amps are NOT Kilovolts-Amps (KVA)Match KVA capacities for microwave
oven design loads
Variac, Wattmeter, Microwave Oven Hookup:
1. Plug Variac into the wall
2. Plug digital wattmeter into the Variac
3. Set the digital wattmeter to read out in Volts
4. Plug microwave oven into the digital wattmeter
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Before every IEC test and NRTE food validation and before you initiate cooking,
adjust the Variac so that the WATTMETER reads 120V with microwave oven at rest
Mains Voltage Influence On Microwave Oven Power Within ANSI C.84.1 Voltage Ranges
106, 113, 120 and 127 Volts AC Mains Supply
Testbed & Protocols1100 and 1200 watt countertop ovens from Emerson, Frigidaire, GE, LG, Kenmore,
Magic Chef and SharpMains Voltage 120VAC (legged down from three phase office park supply)
Staco 2500 KVA Variable AC TransformerGlobal Specialties 2600 KVA Digital Wattmeter
Protocol: IEC 705-1988 (Modified)Three reps per oven per voltage per test
Fluke 52 and Type ‘K’ thermocoupleNIST Thermocouple Calibration
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
127V 120V 113V 106V
MWO 1 930 877 795 671MWO 2 951 871 755 673MWO 3 948 897 776 636MWO 4 937 871 740 644MWO 5 922 876 720 587
Avg. 937 878 757 642Avg.
Power Change
From 120V
7% 0% -14% -27%
IEC 705 (Mod.) 1100 Watt Oven Wattage
At 120V, tested wattage is less than
labeled wattage, as expected
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Labeled Wattage 113V 106V 127V
MWO 1 1100 997 841 1166MWO 2 1100 954 851 1201MWO 3 1100 952 780 1163MWO 4 1100 935 814 1184MWO 5 1100 903 737 1157
Avg. 1100 948 805 1174Avg.
Power Change
From 120V
- -14% -27% 7%
IEC 705 (Mod.) 1100 Watt Oven WattageVirtual 'Box Wattage'
Normalized to their Labeled Wattage…all five microwave ovens exhibit multiple personalities—700 watts to 1200 watts. Which one is correct, and how often will which
one(s) cook safely?
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
127V 120V 113V 106VOven 1 987 887 750 605Oven 2 960 880 808 699
IEC 705 (Mod.) 1200 Watt Oven Wattage
Labeled Wattage 113V 106V 127V
Oven 1 1200 1015 818 1335Oven 2 1200 1102 953 1309
IEC 705 (Mod.) 1200 Watt Oven WattageVirtual 'Box Wattage'
Two 1200 watt ovens, from the same OEM factory,identical inside and out except for front fascia and brand name
The rule, not the exceptionA single oven operates with multiple personalities
Identical model/brand microwave ovens vary greatly one to another, and each to itself daily, in power output
An Engineering Perspective Of…
• IEC Testing Protocols
• Microwave Oven Selection
• Voltage, Power Factor and IEC Oven Power
• The Multi-Disciplinary Challenge
• Q&A and Equipment Demonstration
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Consultants: It takes a village.
The future of food safety is very much in our hands.
Were the impact of NRTE food safety incidents not nearly so immense, few of us would even be here.
(From the grave of philosopher, essayist, poet, and novelist George Santayana)
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
An Engineering Perspective Of…
• IEC Testing Protocols
• Microwave Oven Selection
• Voltage, Power Factor and IEC Oven Power
• The Multi-Disciplinary Challenge
• Q&A and Equipment Demonstration
Microwave Laboratory Architectures, Planning and Methodology For Food Safety
Multi-point temperature measurement
An Engineering Perspective Of…
Microwave LaboratoryArchitectures, Planning and Methodology
For Food Safety
June 21, 2012International Microwave Power InstituteAnnual Symposium Las Vegas NV USA
Steven J. DruckerChief Technology Officer
Microwave Science JV LLCNorcross GA USA
© Microwave Science JV LLC 2012
Microwave Laboratory Architectures, Planning and Methodology For Food Safety