Uploaded May 2021 | Updated September 2026, 2 hours ago
When a capacitor is charged with DC voltage, even if we short its terminals for several second, after removing the short circuit a voltage appears between its terminals. this is named return voltage or recovery voltage. The phenomena behind it is named dielectric absorption and it has to do with polarization of dielectric material used inside capacitor. It takes a while to activate all polarization mechanism and also it takes some time for their relaxation. The recovery voltage can be a few percent of the charged voltage and for HV capacitors it can be sufficiently high to give a severe electric shock, and that is why terminals of HV capacitors must always be kept shorted even if they are completely discharged initially. The recovery voltage is a common diagnostic method that is used to assess general condition of insulation material in high voltage equipment.
Update: regarding the mismatch of time constant of turn on and shorting the capacitor, one more idea is that the space charges are also accumulate in the insulation and because of field dependent conductivity, it can happen that time constant which is kind of proportional to epsilon/sigma will be different during turn on and turn off. during turn on sigma is higher because we have higher electric field due to background voltage, which means a shorter time constant compared to the case when we have shorted the terminals of the capacitor.
Finance:
N=15, subs=356
Available budget (N):
356-100-15*(15+1)=16
Storage limit:
2^ln(356)=58,68
When a capacitor is charged with DC voltage, even if we short its terminals for several second, after removing the short circuit a voltage appears between its terminals. this is named return voltage or recovery voltage. The phenomena behind it is named dielectric absorption and it has to do with polarization of dielectric material used inside capacitor. It takes a while to activate all polarization mechanism and also it takes some time for their relaxation. The recovery voltage can be a few percent of the charged voltage and for HV capacitors it can be sufficiently high to give a severe electric shock, and that is why terminals of HV capacitors must always be kept shorted even if they are completely discharged initially. The recovery voltage is a common diagnostic method that is used to assess general condition of insulation material in high voltage equipment.
Update: regarding the mismatch of time constant of turn on and shorting the capacitor, one more idea is that the space charges are also accumulate in the insulation and because of field dependent conductivity, it can happen that time constant which is kind of proportional to epsilon/sigma will be different during turn on and turn off. during turn on sigma is higher because we have higher electric field due to background voltage, which means a shorter time constant compared to the case when we have shorted the terminals of the capacitor.
Finance:
N=15, subs=356
Available budget (N):
356-100-15*(15+1)=16
Storage limit:
2^ln(356)=58,68
