Portable Appliances and Electrical Equipment Testing
1
Safety standards
Visual check (Class I, II, III)
Items that should be checked:
General appliance testing
Inspection of appliance for sign of damage.
Inspection of flexible supply cable for damage.
Any signs of pollution, moisture, dirt that can jeopardize safety.
Are there signs of corrosion?
Are there signs of overheating?
Inscriptions and marking related to safety must be clearly readable.
Installation of the appliance must be performed according to the user manuals.
During visual inspection the measuring points for the electrical testing have to be determined too.
EN 60950 Safety of information technology equipment
EN 60335 Safety of household and similar electrical appliances
EN 61010 Safety requirements for electrical equipment for measurement, control,
and laboratory use
EN 60598 Safety of luminaries
National standards
German VDE701/702/751 for periodic equipment testing.
UK BS 89
Notes: For Class II and Class III devices visual inspection is often the only applicable safety test!
Classification of appliances (by protection classes)
Class
Marking
Connection to
PE conductor of
installation.
Basic
insulation
Supplementary
or reinforced
insulation
Supply cord
Notes
Examples
I
II
No
No
No connection
to mains
Performed
Performed
Performed / looser
limits
Not needed in
general
Performed
Not needed
Three pole
(L, N, PE)
Two pole,
L, N
Two pole
Installation must
have adequate
earthing resistance
No
Safety low voltage
source, ie 12 V, 24 V
Earth Bond (Class I)
Test current depends on appliance type and selected standard (200 mA, 4 A, 10 A, 25 A)
III
III
Yes
All accessible
metal parts
2
VDE 701/702:
UK regulations:
< 0,3 Ω up to 5 m cord length,
+ 0,1 Ω per 7,5 m cord length, max. 1 Ω.
0.1 Ω up to 0.5 Ω,
depends on fuse
size and supply
cord length
Note: Flexible supply cords must be folded during test!
Result changing means failed test.
3
Class I
Insulation resistance between L-N and PE (Class I, II, III)
Test voltage typically 500V, 250V for not EN 60950 compliant IT equipment.
UK /VDE regulations:
Class
I
Class
II
Class
III
1MΩ
2MΩ
250kΩ
Note: On/Off switches must be closed.
Class I
Class II, III
Portable Appliances and Electrical Equipment Testing
4
5
Leakage current tests (Class I, II, III)
Polarity test / Active polarity test (Class I)
Differential leakage
current test (Class I, II)
Polarity test shows shorts, crossed and opened wires in cords.
Test voltage: Typically = 230 V
Typical reported results from the instrument are: PASS, L open,
N open, PE open, L-PE crossed, N-PE crossed, L-N shorted, L-PE
shorted, N-PE shorted, multiple faults.
Note: The leakage current is measured
as the difference of currents through L
and N conductors.
Example of test on a Class I appliance
Touch leakage test
(Class II, III)
6
Test voltage: Typically = 230 V
The purpose of this test is to ensure the proper operation of
the residual current device. Trip-out measurements verify the
sensitivity of a PRCD at selected residual currents.
Example of test on a Class II, III appliance
Typical limits:
VDE 701/702
PRCD test (Class I, II) Typ (AC, A, B, S, K)
Class I
1 mA/kW or 3.5 mA whichever greater
Test current: 10 mA, 15 mA, 30 mA
Class II
0.5 mA
Typical limits for:
Trip-out times according to EN 61540:
Class I portable 0.75 mA
Class I heating
UK regulations Class I other
General PRCDs (non-delayed)
0.75 mA or 0.75 mA/kW, 5 mA max
3.5 mA
Class II
0.25 mA
Class III
0.5 mA
½xIΔN*
IΔN
5xIΔN
tΔ > 300 ms
tΔ < 300 ms
tΔ < 40 ms
*) Minimum test period for current of ½ΔIΔN, PRCD shall not trip-out.
Note: On/Off switches must be closed. Appliance must be powered on. Each isolated accessible metal part must be checked separately. Appliances with leakage
currents >3.5 mA should be marked.
7
Functional test (Class I, II)
Subleakage test (Class I, II, III)
Measuring instruments permits load testing, which is an effective way of determination if
there are faults in the appliance.
Test: typically
with 30 V to 50 V,
recalculated to 230 V,
between shortened
L-N conductors to PE.
For one, two or three
phase appliances and
equipment.
Test voltage: Typically = 230 V
Example of test on a Class I,II appliance
Class I
Class II, III
Note: The functional test is performed as the last step
of a safety test sequence. It should be run only if all
previous safety tests passed successfully! The functional test would rarely disclose a safety problem!