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September 2003
12
For more information visit: www.cutler-hammer.eaton.com CA03310002E
NEMA Contactors & Starters
IT. Electro-Mechanical
Technical Data and Specifications
Electrical Life — AC-1, AC-2, AC-3 and AC-4 Utilization Categories
Table 8. Utilization Categories
Life Load Curves — Eaton’s Cutler-
Hammer IT. Electro-Mechanical Series
NEMA contactors have been designed
and manufactured for superior life per-
formance. All testing has been based
on requirements as found in IEC
60947-4-1 and conducted by us. When
selecting a contactor, the specifier
must give attention to the specific
load, utilization category and the
required electrical life. For a definition
of Utilization Categories, see Table 8
above.
Note: AC-3 tests are conducted at rated
device currents and AC-4 tests are con-
ducted at six-times rated device currents.
All tests have been run at 460V, 60 Hz.
Actual application life may vary,
depending on environmental condi-
tions and application duty cycle.
Figure 1. Electrical Life — AC-3 Utilization Category
Figure 2. Electrical Life — AC-4 Utilization Category
The International Electrotechnical Commission (IEC) has developed utilization categories for contactors and auxiliary contacts. The IEC utilization categories
are used to define the type of electrical load for estimating electrical life, and do not imply the devices are IEC rated.
Category Typical Application
AC-1 Non-inductive or slightly inductive loads: Resistance furnaces, heating.
AC-2 Slip-ring motors: Starting and stopping of running motors
AC-3 Squirrel cage motors: Starting, switching off motors during running (motors in most industrial applications typically fall into this category).
AC-4 Squirrel cage motors: Starting, plugging
ᕃ
, inching
ᕄ
(very few applications in industry are totally AC-4).
ᕃ
Plugging is stopping or reversing the motor rapidly by reversing the connections while the motor is running.
ᕄ
Inching or jogging is energizing the motor once or repeatedly for short durations to obtain small movements of the motor driven load.
19
10 100 1000
18 4527 90 135 270
Operational Current
00 0 1 2 3 4 5
NEMA Size
10,000,000
1,000,000
100,000
10,000
Operations
Note: Preliminary data.
19
10 100 1000
18 4527 90 135 270
Operational Current
00 0 1 2 3 4 5
NEMA Size
10,000,000
1,000,000
100,000
10,000
Operations
Note: Preliminary data.
Contactor Choice —
■ Decide what utilization category the
application is and choose the
appropriate curve from Figure 1 or
Figure 2.
■ Locate the intersection of the life-
load curve with the operational cur-
rent (le) of the application, as found
on the horizontal axis.
■ Read the estimated contact life
along the vertical axis in number of
operations.
Trip Times
Figure 3. Class 10, 20 and 30 Trip Curves
1000.0
100.0
10.0
1.0
0.1
123456789
2
4
1
6
3
5
10
Trip Time (Seconds)
Trip Class 10 Cold
Trip Class 10 Hot
Trip Class 20 Cold
Trip Class 20 Hot
Trip Class 30 Cold
Trip Class 30 Hot
1
2
3
4
5
6
Multiples of FLA