Siemens SIMOTICS XP 1MB155, Operating Instructions Manual

Page: 26 / 152

Description
3.3 Design
1MB155 / 1MB555
24
Operating Instructions, 03/2018, A5E41926185A
3.3.1 Cooling and ventilation
The machines of this series are three-phase induction machines with a closed primary
(internal) cooling circuit and an open secondary cooling circuit (surface cooling). The surface
cooling varies depending on the version.
3.3.1.1 Machines with a fan
Self-ventilation (standard): Cooling method IC 411 according to EN / IEC 60034-6
Located at the ND end of the stator housing is an air intake cowl that guides the external air
on its way to the motor. The external air is drawn in through openings in the air intake cowl
and flows axially across the outer cooling ribs of the motor frame. The fan wheel for the
external flow of cooling air is attached to the machine shaft.
The fan wheels are bidirectional.
Check the cooling effect below rated speed in the case of frequent switching or braking – or
if the speed is controlled continually below the rated speed.
Forced ventilation (optional): Type of cooling IC 416 in accordance with EN / IEC 60034-6
Cooling that does not depend on the speed is achieved by means of a unit that is
independent of the motor operating state (forced ventilation). This unit is closed to the
outside by a fan cover. It has its own main drive with fan impeller which creates the cooling
air flow required for cooling the motor.
3.3.2 Bearings
In order to support the machine shaft and maintain its position in the non-moving part of the
machine, only 2 rolling bearings are used. One rolling bearing performs the function of a
location bearing that transfers axial and radial forces from the rotating machine shaft to the
non-moving part of the machine. The second rolling bearing is implemented as floating and
support bearing in order to allow thermal expansion inside the machine and transfer radial
forces.
The nominal (calculated) useful life of the bearings according to ISO 281 is at least 20,000
hours with utilization of the permissible radial/axial forces. However, the achievable useful
life of the bearings can be significantly longer in the case of lower forces (e.g. operation with
self-aligning couplings).
Rolling bearings with permanent lubrication are maintenance-free.
The machine is equipped with grease-lubricated rolling bearings.
● The bearings of the standard size machines (up to size 250) are permanently lubricated.
● The bearings of machines size 280 and above have a relubrication facility and automatic
grease quantity control.