Our company manufacturers a test instrument that contains a small
furnace. The furnace assembly consist of a heating element
encapsulated in a silica based cube. The cube provides temperature and
electrical insulation.
Our production units have recently started failing the Hi-Pot test due
to these furnaces. This silica material is slightly conductive. At
1900 volts DC it draws more than 6ma and the Hi-Pot tester shows a
failure. The furnace can conduct anywhere from 5ma to 15ma depending
on the furnace and how well the furnace makes contact with the
grounded chassis that holds it in place.
Testing at different voltages show the resistance of the material does
reduce slightly at higher voltages but it never "arcs".
1. Does this scenario describe a true Dielectric Test Failure?
2. EN61010-1 says in 6.8.4 "No breakdown or repeated flashover shall
occur". What exactly is a "Breakdown" and "flashover"? Can this occur
without "Arcing"?
3. Is there a current limit during this test? I don't see a current
limit in the standard. The 6ma seems like a limitation of our Hi-Pot
tester?
4. The standard shows an alternate test method called Peak Impulse
Test (IEC 60). The furnace seems to pass this test but we are not
setup to perform this test in a production environment. Would this
product be a good candidate for this test? This test looks to be
similar to EN61000-4-5.
Thanks in advance,
Brian Kunde
Group Leader
Compliance Testing Center
LECO Corporation
3000 Lakeview Ave.
St. Joseph, MI 49085
(616) 982-5423 phone
(616) 982-8964 fax
[email protected]
