© by SEMIKRON
/ 2017-09-07 /
Technical Explanation
/ SKiiP
®
4
Page 55/73
7.6
Isolation voltage test (IVT)
During production test the isolation voltage of 5600V
dc
(1700V devices) or 4300V
dc
(1200V devices), each
polarity, is applied to 100% of SKiiP-systems for 1s with a test set up as indicated in Figure 7.8 These
values are also available in the corresponding datasheets.
Figure 7.8: Graphic presentation of the electrical connections by the IVT procedure
The polarity change (with heat sink always grounded) is only possible when the customer uses a
galvanically isolated test control device. Otherwise the plus and minus pole of the isolation test control
device will be shorted.
Please note:
Because of the safety measures during and after the test procedure the heat sink should
be grounded: When a DUT fails with an arc and this is recognized by the test equipment the DUT
typically would be disconnected. However the DUT might be still electrically charged. In this case it
would be dangerous to touch the DUT after the test procedure. In addition to this without grounding the
test voltage could drift and the voltage to ground will be even higher than the nominal test voltage.
All isolation voltage tests must be performed at an ambient temperature of 15…35°C, a relative humidity of
45…75% and an atmospheric pressure of 860…1060 hPa. The standards do not define a certain leakage
current value and, thus, the isolation test (dielectric test) is considered passed if no electrical breakdown
has occurred, i.e. small leakage currents that might occur are not relevant.
There are two types of an isolation damage:
•
Complete breakdown (according the standards)
•
High leakage current (not according the standards!)
According to the corresponding standards it is required to do an IVT with AC voltage. In contrast to the AC-
voltage based IVT a test with DC voltage is recommended because in case of AC IVT the high leakage
currents hardly help in the identification of the isolation problem root cause.
