Slow Speed Function - Siemens SIRIUS 3RW44 User Manual

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Device Functions
6.4

Slow Speed Function

Slow speed factor
Slow speed torque
Typical applications for slow speed function
6-16
This function allows an asynchronous motor to be temporarily operated in both
directions at a speed that is lower than the rated operating speed.
The rated operating speed n
(f) and its number of pole pairs (p).
A resulting slow speed frequency for the motor is defined by a specific thyristor
control. However, it is necessary for this function that only a reduced torque can
be generated in the motor. Due to the possibility of increased heating of the
motor, this function is not suitable for continuous operation.
The slow speed factor and the slow speed torque can be entered individually for
both directions of rotation.
By adjusting the slow speed factor, it is possible to control the motor with a
speed (n
) that is lower than the rated operating speed either in or
Slow speed
against the line phase direction.
The torque generated in the motor can be influenced using the slow speed
torque. The maximum torque which can be created depends on the slow speed
torque that is set. 100 % slow torque can correspond to approx. 30 % of the
motor rated operating torque.
Line frequency
Figure 6-10:Slow speed function
This function is suitable for applications with a low counter torque, e.g. when
machine tools are positioned.
Note
In addition to the set parameters, the motor-specific properties and the
connected load also affect the speed resulting from the slow speed function and
the slow speed torque generated in the motor.
of the motor is determined by its line frequency
motor
60
n
f
----- -
=
Motor
p
n
Nom
n
=
-----------------------------------------------
Slow speed
Slow speed factor
Resulting "slow speed frequency"
SIRIUS 3RW44 manual
GWA 4NEB 535 2195-02 DS 06

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