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2.13 Design with different load cycles
2.14 Overtemperature (Derating)
The DS7 soft starter is designed for a standard load cycle in accordance with
AC-53a of the IEC/EN 60947-2-1 product standard. This means:
3-fold overcurrent for 5 seconds with a duty factor of 75 % and 10 starts per
hour. For example: 4A: AC-53a: 3-5: 75-10
With applications such as water pumps (circulating pumps) the DS7 soft
starter with the assigned rated operational current can be selected. When
different operating frequencies, acceleration and/or starting currents are
involved, the thermal capacity of the DS7 soft starter must be taken into
account in the design.
￫
The appendix (￫ page 219) contains overload curves for various
time, current, and starts-per-hour combinations that can be used
to select the right DS7 soft starter for your application.
All rated operational data of the DS7 soft starter is based on a maximum
ambient air temperature of +40 °C. The maximum permissible ambient air
temperature is +60 °C. Higher ambient air temperatures (> +40 °C) require
a reduced rated operational current I
•
2 percent per degree Kelvin for a stand-alone setup
•
1 percent per kelvin for stand-alone setups with a dedicated DS7-FAN-...
device fan
Example
Ambient air temperature ϑ = +50 °C → 10 K abnormal temperature rise
Soft starter DS7-34xSX032... → I
•
Without a fan: 2 %, 10 K → 20 % I
I
(reduced) = 32 A - 6.4 A = 25.6 A
e
•
With a fan: 1 %, 10 K → 10 % I
I
(reduced) = 32 A - 3.2 A = 28.8 A
e
In combination with the xStart components, further reductions are necessary
since the cooling air flow is impeded. The load cycle must then be
recalculated (￫ section 2.15, "Example of other load cycles").
DS7 Soft starter 09/16 MN03901001Z-EN www.eaton.com
2.13 Design with different load cycles
:
e
= 32 A
e
= 6.4 A,
e
= 3.2 A,
e
2 Engineering
57
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