METREL MI 3399, Instruction Manual With Exercises

Page: 228 / 272

PAT Appliances & Machines Safety Trainer AD 3
– MI 3399
228
4.4.9 Polarity test
Scope of test
The polarity test checks the correctness of polarity of IEC leads, prolongation cords etc.
With this test shorts, crossed and opened wires in cords can be found. This test is
obligatory in countries (e.g. UK, Australia) where the position of line and neutral
conductors is predefined. With the polarity test shorts, crossed and opened wires in cords
can be found.
2
Figure 4-22: Polarity test
Examples of faults
Fault
: L and N wires are crossed in the prolongation cord.
Result : the protection circuit installed in the L input of the appliance will not be functional.
Fault: L and N wires are crossed in the supply lead.
Result :
the fuse installed in the appliance’s L wire will blow only in a case of a short
between L and N but not in a L to PE short.
Figure 4-23: Failure of wires polarity