Charging During Dc Hipot/Insulation Resistance Test - Chroma 19071 User Manual

HIPOT Tester 19071/19072/19073 User's Manual
cause danger if touched.
Don't touch here when
outputting high voltage.
End test confirmation
■
You may touch the DUT, high voltage test cable or high voltage output area like output
terminal in order to alter the layout or perform particular test request, thus be sure to turn
off the power before doing it. For testing the DC HiPot/insulation resistance, the DUT
may contain high voltage after completing the test, so you need to carefully follow the
instructions described in this chapter to perform the work.
3.1.1 Charging During DC HiPot/Insulation Resistance
Test
Charge
■
When doing DC HiPot/insulation resistance test, the DUT, capacitor, test cable, probe
and output terminal, even the test instrument may charge with high voltage. The charged
voltage may need a period of to discharge after the power switch is turned off. Do not
touch any places that may cause electric shock as mentioned above especially at the
moment of turning off the power.
Confirming the charged voltage is discharged totally
■
the test voltage applied as well as the DUT characteristics determine the total discharge
time for the charged voltage. Assuming the high voltage on the DUT is the voltage plus a
0.01uF capacitor paralleling a 100MΩ resistance circuit, then after turning off the power
the voltage on test instrument and DUT takes about 3.5 seconds to decrease to 30V.
Thus when the test voltage is 500V, it needs about 2.8 seconds. Suppose we already
know the time constant of a DUT, you can follow the description above to calculate the
time required for voltage decreasing to beneath 30V after turning off the power. The
method is using the time decreased to under 30V multiplies the time constant ratio as the
figure shown below.
<Formula>
Test Voltage * e
–t/RC
Ex.: 1000V * e
–t/RC
ln = ln 0.03
- t / RC = -3.5
t = 3.5 sec
3-2
–t/RC
= Residual Voltage
= 30V
High Voltage
Output Terminal
Hipot Tester
Return Terminal