### APPENDIX 5B. MICROWAVE OVEN STANDBY POWER TESTING REGRESSION METHODOLOGY

TABLE OF CONTENTS

5B.1 INTRODUCTION ...................................................................................................5B-1 5B.2 METHODOLOGY ..................................................................................................5B-1

LIST OF TABLES
Table 5B.2.1 Active Element Lookup Table ............................................................................5B-1 Table 5B.2.2 Sample Regression Table....................................................................................5B-2 Table 5B.2.3 Sample Regression Output..................................................................................5B-2 Table 5B.2.4 Sample Integration Table ....................................................................................5B-3

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### APPENDIX 5B. MICROWAVE OVEN STANDBY POWER TESTING REGRESSION METHODOLOGY

5B.1 INTRODUCTION DOE considered alternate testing methods to determine standby power over a shorter period than 12 hours that were highly representative in orde r to reduce the test burden on manufacturers. Thus, DOE developed an algorithm by which the standby power consumption and line voltage are measured as the clock is cy cled through all the possi ble digit combinations (in terms of active elements) and then a regression analysis is performed to quantify the impact of the number of lit elements (by digit) and volta ge on power consumption. The results are then integrated across the number of minutes that each active element combination is “on” through the course of the 12 hours.

5B.2 METHODOLOGY The test method would require that the tester enter the fo llowing 18 clock combinations at 15 second intervals into the microwave oven clock display: 1: 11, 1:17, 1:14, 1:15, 1:16, 1:18, 1:41, 1:51, 1:01, 1:55, 7:55, 4:55, 5:55, 6:55, 8:55, 11:55, 12:55, and 10:55. For each programmed time, the average line voltage a nd standby power consumption over a 15-second period are measured. The tester also determin es, for each clock time displayed, the total number of active elements. For the purpose of calculatin g the active number of elements for each digit displayed on the microwave oven display, DOE de veloped the following simplified lookup table.
Table 5B.2.1 Active Element Lookup Table

Digit Displayed Number of Active Elements

Blank / None 0 0 6 1 2 2 5 3 5 4 4 5 5 6 6 7 3 8 7 9 6

The results are then used as inputs to the regression analysis, as shown for illustrative purposes with example data in Table 5B.2.2 below. The regression uses five input factors: the number of active elements for each digit (AE1 through AE4, assuming a four-digit display) and

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### the average line voltage in volts alterna ting-current (VAC), while the standby power consumption in watts (W) is the output.
Table 5B.2.2 Sample Regression Table

Clock Time Average Voltage (VAC) Number of Active Elements by Digit Average Standby Power (W) 1 st 2 nd 3 rd 4 th 1:11 119.718 0 2 2 2 1.16308 1:17 119.8 0 2 2 4 1.22024 1:14 119.8128 0 2 2 4 1.22018 1:15 119.5997 0 2 2 5 1.23941 1:16 119.7364 0 2 2 6 1.2659 1:18 119.7421 0 2 2 7 1.28572 1:41 119.7179 0 2 4 2 1.21773 1:51 119.9457 0 2 5 2 1.24857 1:01 119.9266 0 2 6 2 1.2708 1:55 119.8723 0 2 5 5 1.32908 7:55 119.8025 0 4 5 5 1.38373 4:55 119.7811 0 4 5 5 1.3812 5:55 119.6811 0 5 5 5 1.40734 6:55 119.7248 0 6 5 5 1.43133 8:55 119.758 0 7 5 5 1.45239 11:55 119.7374 2 2 5 5 1.38162 12:55 119.6646 2 5 5 5 1.46521 10:55 119.6489 2 6 5 5 1.48858



### The regression results consist of 6 coefficients: AE1-AE4, voltage, and the intercept. A sample Microsoft Excel regression re sult is shown below in Table 5B.2.3.
Table 5B.2.3 Sample Regression Output SUMMARY OUTPUT

Regression Statistics Multiple R 0.998071 R Square 0.996146 Adjusted R 0.99454 Standard E 0.009197 Observatio 18

ANOVA df SS MS F ignificance F Regressio n 5 0.26235 0.05247 620.3353 4.78E-14 Residual 12 0.001015 8.46E-05 Total 17 0.263365

Coefficient s t andard Err o t Stat P-value L ower 95%Upper 95% L ower 95.0 % U

pper 95.0 % Intercept -2.989038 0.434515 -6.879024 1.7E-05 -3.935764 -2.042311 -3.935764 -2.042311 Volts 0.035709 0.00358 9.975633 3.68E-07 0.02791 0.043508 0.02791 0.043508 AE1 0.047066 0.003238 14.5357 5.57E-09 0.040011 0.054121 0.040011 0.054121 AE2 0.030723 0.001635 18.79208 2.88E-10 0.027161 0.034286 0.027161 0.034286 AE3 0.030894 0.001898 16.28024 1.52E-09 0.02676 0.035029 0.02676 0.035029 AE4 0.032807 0.00169 19.41726 1.97E-10 0.029126 0.036488 0.029126 0.036488



### 5B-2

### The five input factors are input into a sm all integration table which accounts for how many minutes each digit is displaying a given number of active elements per day. A sample integration table appears as Table 5B.2.4 below.
Table 5B.2.4 Sample Integration Table Minutes the Number of Active Elements are on For a Given Digit per Day Active Elements AE1 AE2 AE3 AE4 Standby Energy Consumption 2 360 240 240 144 0.913 Wh 3 0 0 0 0 0.000 Wh 4 0 240 240 288 1.367 Wh 5 0 480 720 432 3.661 Wh 6 0 360 240 432 2.743 Wh 7 0 120 0 144 0.808 Wh Voltage 28.292 Wh Intercept -4.207 Wh Average Daily Total 33.577 Wh 1.399 W Yearly 12.2557 kWh

The integration table then predicts the aver age standby power in W, the daily total watthours (Wh) consumed, and the yearly standby en ergy consumption in kilowatt-hours (kWh), assuming stable 120 VAC input power.

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