ADE7913 datasheet(22/44 Pages) AD

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ADE7912/ADE7913

Data Sheet

Rev. 0 | Page 22 of 44

INSULATION LIFETIME

All insulation structures eventually break down when subjected

to voltage stress over a sufficiently long period of time. The rate

of insulation degradation is dependent on the characteristics of

the voltage waveform applied across the insulation. In addition

to the testing performed by the regulatory agencies, Analog

Devices carries out an extensive set of evaluations to determine

the lifetime of the insulation structure within the ADE7912/

ADE7913 devices. Analog Devices performs accelerated life

testing using voltage levels higher than the rated continuous

working voltage. Acceleration factors for several operating

conditions are determined. These factors allow calculation of

the time to failure at the actual working voltage.

The values shown in Table 8 summarize the maximum

CSA/VDE approved working voltage for 50 years of service life

for a bipolar ac operating condition. In many cases, the

approved working voltage is higher than the 50-year service life

voltage. Operation at these high working voltages can lead to

shortened insulation life in some cases.

The insulation lifetime of the ADE7912/ADE7913 devices

depends on the voltage waveform type imposed across the

isolation barrier. The iCoupler insulation structure degrades at

different rates depending on whether the waveform is bipolar

ac, unipolar ac, or dc. Figure 30, Figure 31, and Figure 32

illustrate these different isolation voltage waveforms.

Bipolar ac voltage is the most stringent environment. The goal

of a 50-year operating lifetime under the bipolar ac condition

determines the maximum working voltage recommended by

Analog Devices. In the case of unipolar ac or dc voltage, the

stress on the insulation is significantly lower. This allows

operation at higher working voltages while still achieving a

year service life.

The working voltages listed in Table 8 can be applied while

maintaining the 50-year minimum lifetime, provided that the

voltage conforms to either the unipolar ac or dc voltage case.

Treat any cross-insulation voltage waveform that does not

conform to Figure 31 or Figure 32 as a bipolar ac waveform, and

limit its peak voltage to the 50-year lifetime voltage value listed

in Table 8.

The voltage shown in Figure 31 is shown as sinusoidal for

illustration purposes only. It is meant to represent any voltage

waveform varying between 0 V and some limiting value. The

limiting value can be positive or negative, but the voltage cannot

cross 0 V.

Figure 30. Bipolar AC Waveform

Figure 31. Unipolar AC Waveform

Figure 32. DC Waveform

RATED PEAK VOLTAGE

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