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Measure current power consumption using ADE7953 power meter

Question asked by tsvetan.filev on Sep 26, 2016
Latest reply on Oct 17, 2016 by dlath

Hi all.

 

We are integrating ADE7953 into a product of ours. We would like to use it to display the current power consumption (that would be the instantaneous power) and as a second step the energy consumption kW/h. We are communicating with the chip over SPI interface. The two current channels A and B are employed to measure two different loads (single phase, two circuits).

Here is the schematics:

 

 

Our procedure is the following:

 

1. Write to config register:  0x4  (HPFEN bit enabled)

2.  Apply optimal settings from datasheet, "REQUIRED REGISTER SETTING", page 18: write 0xAD to reg 0xFE and then write 0x30 to reg 0x120

3. Read regularly (once a sec for example) the meter registers for each channel:

    AVA reg  ->  Papp

    AWATT -> Pa

    AVAR -> Pr

    PFA -> Power factor

    ANGLE_A -> Angle

(We map directly the 32/16 bit registers to int32_t/int16_t type)

4. Use apparent power to display the current (instantaneous) consumption by multiplying by some coefficient (we tried to calculate it but we get different results for different loads).

5. We used an external power meter to measure the load and compare the values.

 

In case of 0 W no load we get:

 

Papp = 876, Pa = 17  Power factor = 0 Angle = -8
Papp = 876, Pa = -9  Power factor = 0 Angle = -8
Papp = 877, Pa = -8  Power factor = 0 Angle = -8
Papp = 876, Pa = 30  Power factor = 0 Angle = -8
Papp = 876, Pa = 19  Power factor = 0 Angle = -8
Papp = 876, Pa = 6   Power factor = 0 Angle = -8
Papp = 876, Pa = -3  Power factor = 0 Angle = -8
Papp = 876, Pa = 3   Power factor = 0 Angle = -8
Papp = 877, Pa = -5  Power factor = 0 Angle = -8
Papp = 876, Pa = 45  Power factor = 0 Angle = -8
Papp = 876, Pa = -2  Power factor = 0 Angle = -8
Papp = 876, Pa = -9  Power factor = 0 Angle = -8
Papp = 876, Pa = 1   Power factor = 0 Angle = -8
Papp = 875, Pa = 6   Power factor = 0 Angle = -8
Papp = 875, Pa = 22  Power factor = 0 Angle = -8
Papp = 876, Pa = 26  Power factor = 0 Angle = -8
Papp = 876, Pa = 16  Power factor = 0 Angle = -8
Papp = 875, Pa = 29  Power factor = 0 Angle = -8
Papp = 875, Pa = 7   Power factor = 0 Angle = -8
Papp = 876, Pa = 0   Power factor = 0 Angle = -8
Papp = 876, Pa = 21  Power factor = 0 Angle = -8
Papp = 876, Pa = 21  Power factor = 0 Angle = -8
Papp = 876, Pa = -21 Power factor = 0 Angle = -8
Papp = 876, Pa = -8  Power factor = 0 Angle = -8
Papp = 875, Pa = 5   Power factor = 0 Angle = -8

 

In case of 63.9 W active load (light bulb) we get:

 

Papp = 3511, Pa = 3486, Power factor = 32535, Angle = -85  
Papp = 3522, Pa = 3495, Power factor = 32520, Angle = -101
Papp = 3504, Pa = 3479, Power factor = 32534, Angle = -37  
Papp = 3512, Pa = 3460, Power factor = 32288, Angle = -90  
Papp = 3536, Pa = 3519, Power factor = 32614, Angle = -68  
Papp = 3517, Pa = 3478, Power factor = 32400, Angle = -59  
Papp = 3559, Pa = 3524, Power factor = 32452, Angle = -68  
Papp = 3500, Pa = 3474, Power factor = 32520, Angle = -73  
Papp = 3511, Pa = 3466, Power factor = 32346, Angle = -60  
Papp = 3533, Pa = 3502, Power factor = 32479, Angle = -103
Papp = 3518, Pa = 3491, Power factor = 32517, Angle = -80  
Papp = 3510, Pa = 3486, Power factor = 32545, Angle = -24  
Papp = 3508, Pa = 3480, Power factor = 32502, Angle = -81  
Papp = 3524, Pa = 3491, Power factor = 32453, Angle = -104
Papp = 3520, Pa = 3486, Power factor = 32454, Angle = -100
Papp = 3550, Pa = 3506, Power factor = 32361, Angle = -84  
Papp = 3542, Pa = 3525, Power factor = 32608, Angle = -47  
Papp = 3526, Pa = 3484, Power factor = 32379, Angle = -70  
Papp = 3528, Pa = 3508, Power factor = 32584, Angle = -70  
Papp = 3533, Pa = 3506, Power factor = 32521, Angle = -102
Papp = 3557, Pa = 3511, Power factor = 32346, Angle = -98  
Papp = 3520, Pa = 3489, Power factor = 32480, Angle = -63  
Papp = 3514, Pa = 3487, Power factor = 32510, Angle = -120
Papp = 3516, Pa = 3482, Power factor = 32445, Angle = -74  
Papp = 3525, Pa = 3500, Power factor = 32539, Angle = -71  
Papp = 3502, Pa = 3464, Power factor = 32407, Angle = -73  
Papp = 3551, Pa = 3511, Power factor = 32395, Angle = -62  
Papp = 3541, Pa = 3511, Power factor = 32483, Angle = -91  
Papp = 3528, Pa = 3491, Power factor = 32430, Angle = -57  

In case of 1.9 W LED load over switching adapter we get:

 

Papp = 880, Pa = 38  Power factor = 0 Angle = -323  <--  At this point only the adapter is plugged in
Papp = 880, Pa = 85  Power factor = 0 Angle = -323
Papp = 880, Pa = 78  Power factor = 0 Angle = -323
Papp = 880, Pa = 81  Power factor = 0 Angle = -323
Papp = 879, Pa = 77  Power factor = 0 Angle = -323
Papp = 879, Pa = 91  Power factor = 0 Angle = -323
Papp = 880, Pa = 120 Power factor = 0 Angle = -323   <--  Turn on LED load at this point
Papp = 879, Pa = 139 Power factor = 0 Angle = -323
Papp = 880, Pa = 139 Power factor = 0 Angle = -323
Papp = 880, Pa = 158 Power factor = 0 Angle = -323
Papp = 880, Pa = 145 Power factor = 0 Angle = -323
Papp = 880, Pa = 141 Power factor = 0 Angle = -323
Papp = 880, Pa = 152 Power factor = 0 Angle = -323
Papp = 881, Pa = 157 Power factor = 0 Angle = -323
Papp = 880, Pa = 132 Power factor = 0 Angle = -323
Papp = 880, Pa = 132 Power factor = 0 Angle = -323  <--  Turn off LED at this point
Papp = 880, Pa = 72  Power factor = 0 Angle = -323
Papp = 880, Pa = 63  Power factor = 0 Angle = -323
Papp = 880, Pa = 44  Power factor = 0 Angle = -323
Papp = 880, Pa = 59  Power factor = 0 Angle = -323
Papp = 881, Pa = 53  Power factor = 0 Angle = -323
Papp = 881, Pa = 73  Power factor = 0 Angle = -323

 

In case of load 13.3 W over transformer we get:

 

Papp = 1473, Pa = 779 Power factor = 17351 Angle = 728
Papp = 1473, Pa = 752 Power factor = 16729 Angle = 728
Papp = 1473, Pa = 774 Power factor = 17219 Angle = 728
Papp = 1473, Pa = 766 Power factor = 17045 Angle = 728
Papp = 1474, Pa = 746 Power factor = 16593 Angle = 728
Papp = 1474, Pa = 762 Power factor = 16941 Angle = 728
Papp = 1474, Pa = 760 Power factor = 16896 Angle = 728
Papp = 1473, Pa = 777 Power factor = 17289 Angle = 728
Papp = 1473, Pa = 806 Power factor = 17932 Angle = 728
Papp = 1472, Pa = 764 Power factor = 17000 Angle = 728
Papp = 1472, Pa = 769 Power factor = 17133 Angle = 728
Papp = 1471, Pa = 770 Power factor = 17153 Angle = 728
Papp = 1472, Pa = 777 Power factor = 17299 Angle = 728
Papp = 1473, Pa = 762 Power factor = 16955 Angle = 728
Papp = 1472, Pa = 791 Power factor = 17609 Angle = 728
Papp = 1472, Pa = 762 Power factor = 16959 Angle = 728
Papp = 1472, Pa = 769 Power factor = 17124 Angle = 728
Papp = 1472, Pa = 779 Power factor = 17341 Angle = 728
Papp = 1472, Pa = 742 Power factor = 16524 Angle = 728
Papp = 1472, Pa = 784 Power factor = 17462 Angle = 728
Papp = 1473, Pa = 763 Power factor = 16967 Angle = 728
Papp = 1473, Pa = 769 Power factor = 17101 Angle = 728
Papp = 1473, Pa = 776 Power factor = 17275 Angle = 728

 

We have the following questions:

1. Why do we get Papp ~ 876 when there is no load and what determines this value

2. Are the ripples (the fluctuations of the power) the same described on Page 24 (Figure 44) ?

Because LFP2 does not have an ideal “brick wall” frequency response, the active power signal has some ripple associated with it. This ripple is sinusoidal and has a frequency equal to twice the line frequency. Because the ripple is sinusoidal in nature, it is removed when the active power signal is integrated to compute the active energy (see the Active Energy Calculation section).

If yes how can we get the average value (the dashed line) without these ripples ?

Does this apply for all parameters: active, reactive, apparent ?

3. We are a bit confused with the values of Power factor and Angle

4. We don't understand why in case 3 the Papp does not change when there is adapter and LED attached but the active power changes.

 

Could you write if we are doing this wrong and what is the best way to do it ?

 

Regards.

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