Air Cooling; Door/Roof Openings - Siemens simovert masterdrives Operating Instructions Manual

10.2006

Air cooling

Siemens AG 6SE7087-7KN50
SIMOVERT MASTERDRIVES

Door/roof openings

An underpressure is created in the openings of the cabinet doors due to
the flow of air. This is dependent on the volumetric flow and the
hydraulic cross-section of the openings.
The flow causes a build-up (over) pressure in the roof or in the top
cover.
As a result of the difference in pressure between the overpressure at
the top and the underpressure at the bottom of the cabinet, a flow of air
is created inside the unit, a so-called arcing short-circuit. This can be
stronger or weaker depending on the volumetric flow and the door/roof
opening cross-section.
As a result of the flow inside the unit, air which is already pre-heated
enters the heat sinks which causes an excessively high component
temperature rise. In addition, a different, more unfavourable operating
point is set for the fan.
If the units are operated with an arcing short-circuit, this will result in the
failure of the units or in their destruction!
An arcing short-circuit must be prevented by the provision of
partitions.
The switch cabinets adjacent to the inverter cabinets must also be
taken into consideration in this case.
The Fig. 5-6 shows the necessary partition measures. Partitions
should be executed up to the cabinet frame and should be designed in
such a way that the discharged air flow is taken around the cabinet
beams and not pressed into them.
Partitions are necessary with all types of protection higher than IP20.
The necessary opening cross-sections are indicated in the table.
The indicated opening cross-section is made up of several holes. In
order to keep the pressure loss here to a minimum, the cross-sectional
surface has to be at least 280 mm
The opening and hole cross-sections ensure functioning even with high
types of protection.
These are implemented by using wire-lattices (wire fabric DIN 4189-
St-vzk-1x0.28) in front of the openings or the filters indicated in the
following. If finer filters are used, the filter surface and thus the opening
cross-section (upwards) have to be adapted accordingly.
If filters are used, the intervals for their replacement must be
observed!
Operating Instructions
2
per hole (e.g. 7 mm x 40 mm).
Installation
5-5