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Rotors are dynamically balanced with half-key acc. to ISO 8821, so that all elements which are
directly mounted on DE motor shaft must be also dynamically balanced in the same way. During
manipulation with the motor it is not allowed to hang the motor by the lifting ring screwed in the shaft.
This kind of manipulation can cause permanent damage of bearing assembly.
Belt drives put a lot of stress on the motor because of relatively high radial forces. When dimensioning belt
drives, apart from the instructions and calculation programmes issued by the manufacturers of the belts, it must
be ensured that the radial force permissible at the shaft end of the motor as stated in our data is never
exceeded by the pull and pre-tensioning of the belt. When pre-tensioning the belt during installation the
instructions of the belt manufacturers must be strictly adhered to.
Relatively large radial forces or masses can be taken up at the end of the motor shaft by the use of cyclindrical
roller bearings (“heavy bearing arrangement” VL). The minimum radial force at the shaft end must be a quarter
of the permissible radial force. The permissible shaft end load is to be taken into account. The information can
be taken from the tables and diagrams in the design selection data.
If the radial force falls below the minimum value, damage to the bearings can be caused
within a few hours. Test runs in no-load state only permissible for a short period.
Inspection of the belt drive
In case of belt drive make sure to regularly inspect the belt drive during the initial operating hours. The
drive belt will have to be inspected and retightened – if necessary - after an operating period of
between 0.5 and 4 hours under full load and then in intervals of about 24 operating hours.
Control of acquired belt tension force is carried out on the basis of its deflection caused by force Fg.
To measure the deflection position the measuring gauge with the load hook A in the center of the belt
run. Zero the trailing pointer. Apply the test force in accordance with scale C. For this, pull the
measuring gauge at a 90 degrees angle away from the belt run. Read the depth of impression on
scale D of the trailing pointer. Relation of the belt tension force Fp, pressure Fg and deflection can be
expressed by the following approximate equation:
(
)
(
)
N
F
f
a
F
g
p
20
...
10
cos
/
25
,
0
−
=
γ
.
Value of force Fg for belts is determined according to its cross section with keeping the deflection not
smaller than
a
f
016
,
0
>
(a – axis distance), for belts specified in table 1.
Belt Cross
Section
SPZ
SPA
SPB
SPC
Y
Z
A
B
C
D
E
F
g
[N]
25...27
45...50
75
125…140
13
24
40
70
120
240
360
If necessary, properly set the belt pretension until the specified depth of impression f is reached. If
the drive belt is not properly tightened, the result will be an inadequate transmission of power and a
premature failure of the drive belt. A too high pretension will additionally be the cause of bearing
damages. When tightening the belt, make sure that the lateral alignment of the belts does not deviate
by more than 1 degree
DRIVEN
MACHINE
COUPLING
ELECTRIC
MOTOR
