Eaton DS7 Series, Manual

Page: 61 / 240

2 Engineering
2.13 Design with different load cycles
DS7 Soft starter 09/16 MN03901001Z-EN www.eaton.com
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2.13 Design with different load cycles
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.
2.14 Overtemperature (Derating)
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
e
:
• 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
e
= 32 A
• Without a fan: 2 %, 10 K → 20 % I
e
= 6.4 A,
I
e
(reduced) = 32 A - 6.4 A = 25.6 A
• With a fan: 1 %, 10 K → 10 % I
e
= 3.2 A,
I
e
(reduced) = 32 A - 3.2 A = 28.8 A
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”).
￫
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.