Charge Resistors For Automated Ir Testing - Saluki STB6684 Operation Manual

STB6684/A Operation Manual
Chapter 6 Measurement Procedures and Examples

6.5 Charge Resistors for Automated IR Testing

Scope
Automated testing of capacitor insulation resistance (IR) with STB6684/STB6684A IR tester
often requires a stepwise charging of the capacitor before the acutual resistance measurement.
This could be due to the fact that the charging time is longer than the time between
measurements or to secondary effects like post charging ("dielectric absorption") of foil
capacitors. The latter makes it necessary to ensure that the capacitor is fully charged before
measurement. This application note describes the fundamental of calculating the charge resistor
values.
General
Fig. 6.5.1 shows the set-up for STB6684 with two HV supplys, one for precharging and one for
fine charging and measurement.
HT2 HT1 Current Measurement Board
DB62X
Rdisch Rpr1 Rpr2 Rpr3 Rf1 Rf2
Discharge station Pre-charge stations Fine charge stations
Capacitor propagation
Fig. 6.5.1 Example of IR testing set-up
Normally, there is more than 3 precharge and more than 10 fine charge stations, but for simplicity
the number is reduced. In the example there is three precharge stations and two fine charge stations
before the measure station. The precharge stations perform the bulk charging of the capacitors. The
purpose of the fine charge stations is to ensure that the capacitor is charged to the exact test voltage.
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