Page 94 - contactors_motor_protection_for_rolling_stock_application

AF09(Z)B ... AF370B 3-pole contactors

Electrical durability and utilization categories

General
Utilization categories determine the current making and breaking conditions relating to the characteristics of the loads to be
controlled by the contactors. International standard IEC 60947-4-1 and European standard EN 60947-4-1 are the standards to
2 be referred to.
If Ic is the current to be broken by the contactor and Ie the rated operational current normally drawn by the load, then:
– Categories AC-1 and AC-3: Ic = Ie
– Category AC-2: Ic = 2.5 x Ie
– Category AC-4: Ic = 6 x Ie
Generally speaking Ic = m x Ie where m is a multiple of the load operational current.
On next pages, the curves corresponding to categories AC-1, AC-3 and AC-4 represent the electrical durability variation of
standard contactors in relation to the breaking current Ic.
Electrical durability is expressed in millions of operating cycles.

Curve utilization mode
Electrical durability forecast and contactor selection for categories AC-1, AC-2, AC-3 or AC-4
• Note the characteristics of the load to be controlled:
– Operational voltage .......................................... Ue
– Current normally drawn .................................... Ie (Ue / Ie / kW relation for motors, see "Motor rated operational powers and currents").
– Utilization category .......................................... AC-1, AC-2, AC-3 or AC-4
– Breaking current .............................................. Ic = Ie for AC-1 and for AC-3 ; Ic = 2.5 x Ie for AC-2 ; Ic = 6 x Ie for AC-4
• Define the number of operating cycles N required.
• On the diagram corresponding to the operational category, select the contactor with the curve immediately above the inter-
section point (Ic ; N).

Electrical durability forecast and contactor selection for mixed duty motor control: AC-3 (Ic = Ie) type switching off while
"motor running" and, occasionally, AC-4 (Ic = 6 x Ie) type switching off while "motor accelerating"
• Note the characteristics of the motor to be controlled:
– Operational voltage ...................................................... Ue
– Current normally drawn while "motor running" ............... Ie (Ue / Ie / kW relation for motors, see "Motor rated operational powers and currents")
– Breaking current for AC-3 ............................................ Ic = Ie
– Breaking current for AC-4 while "motor accelerating" ..... Ic = 6 x Ie
– Percentage of AC-4 operating cycles ............................ K (on the basis of the total number of operating cycles)
• Define the total number of operating cycles N required.
• Note the smallest contactor rating compatible for AC-3 (Ue / Ie) on Main pole utilization characteristic table (see “Technical data”).
• For the selected contactor make a note of the following in relation to the voltage using diagram AC-3 in next pages:
– The number of operating cycles A for Ic = Ie (AC-3)
– The number of operating cycles B for Ic = 6 x Ie (AC-4)
• Calculate the estimated number of cycles N’ (N’ is always below A)
N'= A
1 + 0.01 K (A/B - 1)
• If N' is too low in relation to the target N, calculate the estimated number of cycles for a higher contactor rating.

Case of uninterrupted duty
For uninterrupted duty, some verifications of preventing maintenance are necessary to check the functionality of the concerned
product (consult us).
The combinated effect of environmental conditions and the proper temperature of the product may require some disposals. As
a matter of fact, for this duty, the use duration prevails over the number of operating cycles.
1SBC101837S0201 - rev. A

2/82 | ABB