METREL MI 3399, Instruction Manual With Exercises

Page: 234 / 272

PAT Appliances & Machines Safety Trainer AD 3
– MI 3399
234
Figure 4-32: Active polarity test
4.5 Testing the safety of machines and switchboards
4.5.1 Find out more about testing safety of machines.
Typical hazardous situations related to electrical equipment are:

Failures or faults in the electrical equipment resulting in the possibility of electric
shock or electrical fire.

Failures or faults in control circuits resulting in the malfunctioning of the machine.

Disturbances or disruptions in power sources as well as failures or faults in the
power circuits resulting in the malfunctioning of the ma-chine.

Loss of continuity of circuits that depends on sliding or rolling contacts, resulting in
failure of a safety function.

Electrical disturbances either from outside the electrical equipment or internally
generated, resulting in the malfunctioning of the machine.

Release of stored energy (either electrical or mechanical) resulting in electric
shock or unexpected movement that can cause injury.

Audible noise at levels that cause health problems to persons.

Surface temperatures that can cause injury.
To verify the electrical safety of machines the appropriate measurements should be
performed:

After erection of machine.

After installation of machine.

After upgrading or changing of machine.

During periodic retests of machine.
4.5.2 Verification of safety of machines
According to IEC/EN 60204, Ed.5 verification of electrical safety of machines is performed
by inspection and measurements:

Inspection that the electrical equipment complies with its technical documentation.

Verification of protection against indirect contact by automatic disconnection.

Insulation resistance test.

High voltage test.

Protection against residual voltages.