26 l
Installation, operation and maintenance manual – Squirrel cage motor – WGM20 Line 14108242
4.8.2
Base loads
Based on Figure 4.6, base loads can be calculated by the
equations:
Where: F1 and F2 - Reaction of the feet on the base (N)
g - Acceleration of gravity (9.81m/s²)
m - Motor mass (kg)
Cmax - Maximum torque (Nm)
A - Obtained from the motor dimensional drawing
(m)
Figure 4.6: Foundation loads
4.8.3
Base types
4.8.3.1
Concrete base
The type and size of the base, bolts and anchoring plates
depend on the motor size and type.
Example of base preparation:
Remove all the dirt from the foundation to ensure a
proper binding between the foundation blocks and the
mortar.
Fasten the foundation blocks to the motor feet using
bolts.
Use shims of different thicknesses (total thickness of
approximately 2 mm) between the motor feet and the
foundation surfaces in order to obtain a precise vertical
alignment.
In order to ensure the centralization of the bolts
regarding the foot holes, use a metallic or a cardboard
(prespan) sheet as bushing, making possible a precise
horizontal alignment later.
Place shims or leveling bolts under the foundation
blocks to ensure proper leveling and perfect alignment
of the motor with the driven machine. After the mortar
is applied, the alignment must be precisely controlled.
Occasional small corrections may be done with
washers or metal sheets or by readjusting the clearance
of the fastening bolts.
Tighten all the fastening bolts firmly. Make sure the
motor feet surfaces are supported evenly without
distorting the motor frame.
For precise fixation, introduce the tapered pins after
finishing the test.
4.8.3.2
Sliding base
In case of pulley drive, the motor must always be mounted
on a sliding base (rails), and the lower part of the belt must
be tightened.
The rail closer to the driving pulley must be mounted so
that the positioning bolt is placed between the motor and
the driven machine. The other rail must be mounted with
the bolt in the opposite position, as shown in Figure 4.7.
The motor is bolted on rails and positioned on the
foundation.
The driving pulley is then aligned so that its center and the
center of the driven pulley are in the same plane, and the
motor and machine shafts are perfectly parallel.
The belt must not be stretched too much. After the
alignment, the rails are fixed.
Figure 4.7: Sliding base
4.8.3.3
Metal base
The motor must rest evenly on the metal base in order to
prevent deformations of the frame. Occasional errors in
the height of the surface that supports the motor feet can
be corrected with shims (a maximum height of 2 mm is
recommended).
Do not remove the machines from the common base to
align them. The base must be leveled on the foundation by
using spirit levels or other leveling devices.
When a metal base is used to align the height of the motor
shaft end with the machine shaft end, it must be leveled
on the concrete base.
After the base has been leveled, the anchor bolts
tightened and the couplings checked, then the metal base
and the anchor bolts are cemented.
4.8.3.4
Anchor bolts
Anchor bolts are devices to fasten the motors directly on
the foundation when the motors are applied with elastic
coupling. This coupling type is characterized by the
absence of loads on the bearings.
The anchor bolts must neither be painted, nor present
rust, since that impairs the adhesion to the concrete,
loosening them.
Figure 4.8: Anchor bolts
4.8.4
Natural frequency of the base
In order to ensure a safe operation, the motor must be
precisely aligned with the coupled equipment and both
must be properly balanced.
As a requirement, the motor installation base must be flat
and meet the requirements of DIN 4024-1 standard.
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