METREL MI 3399, Instruction Manual With Exercises

Page: 218 / 272

PAT Appliances & Machines Safety Trainer AD 3
– MI 3399
218
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Galvanic separation of measuring circuit is preferred (obligatory for VDE tests).
Otherwise additional current paths via ground can occur (through uninsulated floor,
other connections with earth like EMC shields etc.). That can result in too low
readings.
4.4.3 Insulation
Scope of test
Insulation resistance between live conductors and all accessible conductive parts
(earthed and isolated) is checked. This test discloses faults caused by pollution, moisture,
deterioration of insulation material etc.
Figure 4-5: Insulation resistance test for Class I device
The capacitive part of leakage currents is not measured because of the DC test voltage.
High DC voltage test signal is applied between connected live pins and PE contact of
supply cord. Unearthed accessible metal parts are NOT included in this test and are
measured as Class II items.
Figure 4-6: Insulation resistance test for Class II device
High DC voltage test signal is applied between connected live pins and accessible
isolated metal part.