IMO Technical Brochure

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Utilisation Categories
Utilisation Categories as are covered in the European Standards EN 60947-1 & EN60947-3 and dene an equipment’s intended application.
The list of both AC and DC categories for low-voltage switchgear and controlgear are stated in EN 60947-1 Annex A along with the relevant
product standards.
Manufacturers of both switchgear and controlgear should include in their technical product data all the operational ratings for the utilisation
categories for which a product is designed and as such this should remove the confusion for users and designers in their selection of the
correct product.
If we consider PV installations where there are requirements for switchgear being used on the DC side then the system falls typically within
two categories below (for which the relevant standard is EN 60947-3)
DC-21 Switching of resistive loads, including moderate overloads
DC-22 Switching of mixed resistive and inductive loads, including moderate overloads
DC-PV1 Switching of single PV string(s) without reverse and overcurrents
DC-PV2 Switching of several PV strings with reverse and overcurrents
Compliance to the EN60947-3 utilisation categories involves the products completing a number of tests, these include the
“Making and Breaking Capacity” (section 7.2.4.1/D7.2.4.1) and “Operational Performance” (section 7.2.4.2/D7.2.4.2).
Verication of the operational making and breaking capacities are stated by reference to the rated operational voltage and rated operational
current according to Table 3 and Table D7 (see extracts below).
Test Conditions for Making & Breaking Capacities
Test Conditions for Number of On Load Operating Cycles
I=making current I
c
=breaking current I
e
=rated operational current
U=applied voltage U
e
=rated operational voltage U
r
=operational frequency or d.c recovery voltage
Utlilisation
categories
Rated
operational
categories
Making Breaking
Number
of
operating cycles
I/I
e
U/U
e
L/R
ms
I
c
/I
e
U
r
/U
e
L/R
ms
DC-21A - DC-21B All values 1.5 1.05 1 1.5 1.05 1 5
DC-22B All values 4 1.05 2.5 4 1.05 2.5 5
DC-PV1 All values 1.5 1.05 1 1.5 1.05 1 5
DC-PV2 All values 4 1.05 1 4 1.05 1 5
Utilisation
categories
Number of
operating
cycles per
hour
Number of operating cycles
A categories B categories
Without current With current Total Without current With current Total
DC-21A/B & DC-22B 120 8,500 1,500 10,000 1,700 300 2,000
DC-PV1 & DC-PV2 120 9,700 300 10,000 - - -
Utilisation
categories
Rated
operational
categories
Making Breaking
I/I
e
U/U
e
L/R
ms
I
c
/I
e
U
r
/U
e
L/R
ms
DC-21A - DC-21B All Values 1 1 1 1 1 1
DC-22B All Values 1 1 2 1 1 2
DC-PV1 All Values 1 1 1 1 1 1
DC-PV2 All Values 1 1 1 1 1 1