INTRODUCTION
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INTRODUCTION
The importance of testing... User safety
In an era of soaring liability costs, original manufacturers of electrical and electronic
products must make sure every item is as safe as possible. All products must be designed
and built to prevent electric shock, even when users abuse the equipment or by-pass built
in safety features.
To meet recognized safety standards, one common test is the "dielectric voltage-withstand
test". Safety agencies which require compliance safety testing at both the initial product
design stage and for routine production line testing include: Underwriters Laboratories,
Inc. (UL), the Canadian Standards Association (CSA), the International Electrotechnical
Commission (IEC), the British Standards Institution (BSI), the Association of German
Electrical Engineers (VDE) and (TÜV), the Japanese Standards Association (JSI). These
same agencies may also require that an insulation resistance test and high current ground
bond test be performed.
The Dielectric Withstand (Hipot) Test....
The principle behind a dielectric voltage - withstand test is simple. If a product will
function when exposed to extremely adverse conditions, it can be assumed that the
product will function in normal operating circumstances.
The most common applications of the dielectric-withstand test are:
·
Design (performance) Testing.... determining design adequacy to meet service
conditions.
·
Production Line Testing.... detecting defects in material or workmanship during
processing.
·
Acceptance Testing.... proving minimum insulation requirements of purchased parts.
·
Repair Service Testing.... determine reliability and safety of equipment repairs.
The specific technique varies with each product, but basically, during a dielectric voltage -
withstand test, an electrical devise is exposed to a voltage significantly higher than it
normally encounters. The high voltage is continued for a given period of time.
During the test, all "stray" current flow to ground is measured. If, during the time the
component is tested, stray current flow remains within specified limits, the device is
assumed to be safe under normal conditions. The basic product design and use of the
insulating material will protect the user against electrical shock.
The equipment used for this test, a dielectric-withstand tester, is often called a "hipot" (for
high potential tester). The "rule of thumb" for testing is to subject the product to twice its
